"ÍNDICE DE COORDENAÇÃO E PARAMETROS FISIOLÓGICOS A INTENSIDADES SUB-MÁXIMAS DE NADO"

Texto

(1)COORDINATIVE AND PHYSIOLOGICAL CHARACTERIZATION OF MODERATE AND HEAVY SWIMMING INTENSITIES. Dissertação apresentada às provas de Mestrado no ramo das Ciências do Desporto, na área de especialização de Treino de Alto Rendimento Desportivo, orientada pelo Professor Doutor Ricardo Fernandes e pelo Professor Doutor João Paulo Vilas-Boas, ao abrigo do Decreto-lei nº 74/2006 de 24 de Março. Este trabalho insere-se no projecto PTDC/DES/101224/2008 (FCOMP-010124-FEDER-009577) da Fundação da Ciência e Tecnologia. Presentation of Master Thesis in Sport Sciences, with specialization in High Performance Sports Training, under the supervision of Professor Dr. Ricardo Fernandes and Professor Dr. João Paulo Vilas-Boas, according to Decret-law nº. 74/. 2006. of. 24. of. March.. This. work. is. part. of. the. project. PTDC/DES/101224/2008 (FCOMP-01-0124-FEDER-009577) of Foundation for Science and Technology.. Pedro André Carneiro Morais Porto, 2011. I.

(2) FICHA DE CATALOGAÇÃO. Morais, Pedro (2011). Coordinative and physiological characterization of moderate and heavy swimming intensities. Porto: P. Morais. Master Thesis in Sport Sciences. University of Porto, Faculty of Sport.. KEY WORDS: SWIMMING, ARM COORDINATION, ENERGY COST, ANAEROBIC THRESHOLD. PALAVRAS CHAVE: NATAÇÃO, COORDENAÇÃO, CUSTO ENERGÉTICO, LIMIAR ANAERÓBIO.

(3) To all the swimmers that I had and have the pleasure to work with. To them I owe my motivation to continue to learn and investigate..

(4)

(5) ACKNOWLEDGMENTS At this point, I would like to express my gratitude to all that have supported me on the process of elaboration of this Masters Thesis.. To Prof. Dr. Ricardo Fernandes, for his orientation, interest and patience throughout this thesis. I also want to thank him for his contribute and support through my academic and professional career. I owe him a part of what I am today…. To Prof. Dr. João Paulo Vilas-Boas, for his scientific example and his inexhaustible wisdom. I also want to thank him for his interest and support throughout this work.. To Dr. Pedro Figueiredo for his contribute and interest on the elaboration of this thesis. To Eng. Pedro Gonçalves, for his help and patience to simplify “monsters” in workable images…. To Inês, not only for her contribute and help on the elaboration of this thesis, but must of all, for her friendship.. To Rodolfo and Manel for their interest and support along this journey.. To Vitória for her help and support in the final phase of this work.. To my parents, who by their efforts and sacrifices, I owe everything..

(6)

(7) This Thesis is based on the following papers, and abstracts which are referred in the text by their Arabic and Roman numerals, respectively:. 1. Morais, P.; Keskinen, K.L.; Seifert, L.; Chollet, D.; Vilas-Boas, J.P.; Fernandes, R.J. (2010). Relationship between Arm Coordination and Energy Cost in Front Crawl Swimming. In: Kjendlie, P. L., Stallman, R. K., Cabri, J. (Eds), Biomechanics and Medicine in Swimming XI. Norwegian School of Sport Science, pp. 74-76.. 2. Morais, P.; Vilas-Boas, J.P.; Seifert, L., Chollet, D., Fernandes, R. (2011). Arm Coordination, Stroke Parameters and Anaerobic Threshold assessment in Front Crawl Swimming. Submitted for publication to the Int J Sports Med.. I. Morais, P.; Vilas-Boas, J.P.; Seifert, L.; Chollet, D.; Keskinen, K. L. ; Fernandes, R. (2008). Relationship between energy cost and the index of coordination in front crawl – a pilot study. J Sports Sci; 26 (Supplement 1): 11. II. Morais, P.; Ribeiro, J.; Balonas, A.; Figueiredo, P.; Seifert, L.; Chollet, L.; Keskinen, K. L.; Vilas-Boas, J. P.; Fernandes, R. (2008). Arm coordination and intracyclic velocity variation during a time limit test at the velocity of VO2max. Archivos de Medicina del Deport, XXV (6)128: 587.. VII.

(8)

(9) TABLE OF CONTENTS. Chapter 1 General Introduction.. 1. Chapter 2 Relationship between Arm Coordination and Energy Cost in Front Crawl Swimming. Chapter 3 Coordinative and physiological characterization of moderate and heavy swimming intensities.. 7. 17. Chapter 4 General Discussion.. 33. Chapter 5 Conclusions. 43. Chapter 6 Suggestions for future research.. 45. Appendix I Relationship between energy cost and the index of coordination in front crawl – a pilot study. Appendix II Arm coordination and intracyclic velocity variation during a time limit test at the velocity of VO2max. Chapter 7 References.. 47. 51. 55. IX.

(10)

(11) INDEX OF FIGURES Figure 1. Direct relationships between velocity and IdC, and velocity and C (upper panel), and between IdC and C (lower Chapter 2. panel) for the total group of swimmers. Linear and. 13. polynomial regression equations and correlation values are indicated. Figure 1. Determinations of inflexion/drop point of blood lactate concentrations [La-] commonly defined as the individual anaerobic threshold (AnTind) index of coordination Chapter 3. (IdCinflex), stroke rate (SRinflex), and stroke length (SLdrop),. 23. from the relation between these parameters and swimming velocity. Appendix II. Figure 1. Evolution of IdC in the TLim-vVO2max test.. XI. 53.

(12)

(13) INDEX OF TABLES. Table 1 Chapter 2. O2max, IdC and C. obtained in each 200m step of the incremental protocol (n=7).. 12. Table 1. Means and standard deviations for swimming Chapter 3. velocity, index of coordination, stroke rate, stroke length and 24 [La-] for n=11. Table 2 Mean and standard deviation values for [La-] at rest, maximal [La-], [La-] corresponding to the individual anaerobic threshold, index of coordination value corresponding to the IdCinflex, stroke rate value corresponding to the SRinflex, stroke 25 length value corresponding to SLdrop, and the corresponding velocities to this phenomena, for total sample and both genders. Table 3. Correlation matrix between the velocity of the index of coordination inflexion point, individual anaerobic threshold, 26 stroke rate inflexion point and stroke length drop point.. Appendix I. Table 1. Mean values of Index of Coordination (IdC) and 49. Energy Cost (C).. XIII.

(14)

(15) ABSTRACT The index of coordination, that represents the time gap between the propulsion of the two arms, is a new area of interest in front crawl swimming. This parameter expresses the relation between the propulsive actions and the non propulsive actions of the stroke. The general purpose of this thesis was twofold: (i) to characterize the arm coordination and energy coast in front crawl swimming, observing the relationship between these tow parameters and (ii) to characterize arm coordination, stroke parameters and individual anaerobic threshold, looking to the relationship between these parameters in swimmers of both genders. Each swimmer performed an intermittent incremental test, with increments of 0.05m.s-1 each 200m stage (and 30s intervals), until exhaustion. Initial velocity was established according to the individual level of fitness and was set at the swimmer‟s individual performance on the 400m freestyle minus seven increments of velocity. Blood lactate concentrations were collected from the ear lobe, were assessed at rest, during the 30s intervals, immediately after each step and 1, 3, 5 and 7min after the end of the protocol. For each stage, 2 arm strokes were analysed to every 50m of the 200m. Results pointed out that index of coordination are related with physiological parameters. It was observed his relation with the energy cost of swimming (r=0.97, p<0.01). Furthermore it was observed that index of coordination does not increase linearly with swimming velocity, and a critical point was observed. The intensity at was observed this non-linear increase is highly related (r=0.82, p<001) with the intensity associated with the individual anaerobic threshold as with significant changes on stroke rate and a stroke length (r=0.79, p<0.01; r=0.74, p<0.01). Thus, it seems that furthermore other factors, changes on arm coordination could be connected to modifications on physiological parameters.. KEY WORDS:. SWIMMING,. ARM. COORDINATION,. ANAEROBIC THRESHOLD. XV. ENERGY. COST,.

(16)

(17) RESUMO O índice de coordenação, que representa o intervalo de tempo entre a propulsão dos membros superiores na técnica de crawl, é uma área de interesse recente na natação. Este parâmetro expressa a relação entre as acções propulsivas e as acções não propulsivas da braçada. Os objectivos gerais desta tese foram: (i) caracterizar a coordenação entre os membros superiores e o custo energético no nado de crawl, observando a relação entre estes parâmetros e (ii) caracterizar a coordenação dos membros superiores, parâmetros gerais da braçada e o limiar anaeróbio individual, analisando a relação entre estes parâmetros em nadadores de ambos os géneros. Cada nadador realizou um teste intermitente e incremental, com incrementos de 0.05ms-1 a cada patamar de 200m (e 30s de intervalo), até a exaustão. A velocidade inicial foi estabelecida de acordo com o nível individual de cada nadador na prova 400m livres, menos sete incrementos de velocidade. As concentrações de lactato sanguíneo foram recolhidas do lóbulo da orelha, em repouso, durante os 30s de intervalo, imediatamente após cada patamar e 1, 3, 5 e 7min após o término do protocolo. Para cada patamar, foram analisados dois ciclos de braçada em cada 50m. Os resultados revelaram que o índice de coordenação se encontra relacionado com o custo energético (r=0.97, p<0.01), e que o índice de coordenação não aumenta linearmente com a velocidade de nado, tendo sido identificado um ponto crítico, em que se assiste a um aumento não linear dos valores deste parâmetro. A intensidade a que foi observado o aumento não linear correlaciona-se (r=0,82, p <0,01) com a intensidade associada ao limiar anaeróbio individual, bem como com alterações significativas na frequência de braçada e distância por ciclo (r=0,79, p<0.01; r=0,74, p<0.01). Assim, para além de outros factores, os parâmetros fisiológicos parecem influenciar o comportamento da coordenação dos membros superiores no nado de crawl. PALAVRAS-CHAVE: NATAÇÃO, COORDENAÇÃO, CUSTO ENERGÉTICO, LIMIAR ANAERÓBIO. XVII.

(18)

(19) RESUME L'indice de coordination, qui représente l'écart de temps entre la propulsion des deux bras, est un nouveau domaine d'intérêt en natation. Ce paramètre exprime le rapport entre les actions propulsives et les actions non propulsives de la course. L'objectif général de cette thèse était: (i) de caractériser la coordination du bras et de la côte de l'énergie dans le nage de crawl, en observant la relation entre ces paramètres et (ii) de caractériser la coordination de bras, les paramètres biomécaniques générales et individuelle seuil anaérobie, la recherche sur la relation entre ces paramètres chez les nageurs des deux sexes. Chaque nageur a effectué un test incrémental intermittente, avec des incréments de 0,05 ms-1 200m chaque étape (et 30s intervalles), jusqu'à l'épuisement. La vitesse initiale a été établie la performance individuelle du nageur sur le 400m nage libre moins sept paliers de vitesse. Concentrations sanguines de lactate ont été recueillies à partir du lobe de l'oreille, ont été évalués au repos, dans les années 30 intervalles, immédiatement après chaque étape et 1, 3, 5 et 7 minutes après la fin du protocole. Pour chaque étape, 2 cycles de bras ont été analysées pour tous les 50m du 200m. Résultats fait remarquer que l'indice de coordination sont liés à des paramètres physiologiques. Il a été observé sa relation avec le coût de l'énergie (r = 0,97, p <0,01). En outre, il a été observé que l'indice de coordination n'augmente pas linéairement avec la vitesse de nage, et un point critique a été observé. L'intensité a été observée à cette augmentation non-linéaire est fortement relaté (r = 0,82, p <001) avec l'intensité associée au seuil anaérobie individuel que des changements significatifs sur la fréquence de cycle et de la distance de cycle (p r = 0,79, p <0,01 ; r = 0,74, p <0,01). Ainsi, il semble que les facteurs en outre, les changements sur la coordination bras pourraient être reliés à des modifications sur les paramètres physiologiques.. MOTS. CLÉS:. NATATION,. COORDENATION. ÉNERGÉTIQUE, SEUIL ANAÉROBIE. XIX. DU. BRAS,. COÛT.

(20)

(21) ABBREVIATIONS AND SYMBOLS Abbreviation/Symbol - Term (unit). AnT - anaerobic threshold C - energy cost of exercise cm - centimetre D - drag Ė – energy expenditure e.g. - example et al. - and collaborators i.e. - this is IdC – index of coordination AnTInd - individual anaerobic threshold IVV – intracycle velocity variation J - joules kg - kilogram -. -1. [La ] - blood lactate concentrations (mmol.l ) -1. l.min - liter per minute m - meter min - minute mmol.l-1 - millimoles per litter -1. m.s - meter per second n - number of subjects p - probability r - correlation coefficient s - second SD - standard deviation SLdrop - stroke length drop point. XXI.

(22) SPSS - statistical package for social sciences SRinflex - stroke rate inflexion point TLim-vVO2max - Time Limit test (to exhaustion) at the minimum velocity of VO 2max v – swimming velocity vAnT - velocity corresponding to the anaerobic threshold.  O2 - volume of oxygen consumed (ml.min-1 or ml.kg-1.min-1) V  O2max - maximal volume of oxygen consumed (ml.min-1 or ml.kg-1.min-1) V < - less than > - higher than * - denotes a significant difference % - percentage ± - more or less = - equal. XXII.

(23) CHAPTER 1 GENERAL INTRODUCTION. Swimming performance is influenced by a large group of factors. However, the area of confluence between the biomechanical and the bioenergetical factors the biophysics – represent, since the 1990‟s, one of the major themes of interest in swimming literature (Pendargast et al., 2003; Pendargast et al., 2006; Lafitte et al., 2004; Barbosa et al., 2005). Among the biomechanical factors, the stroke parameters (stroke rate, stoke length and stroke index) are considered as very important for swimmer‟s skill characterization. Furthermore, Chatard et al. (1990) observed that the temporal organization of the stroke, in high level swimmers, also represent an important mean of characterization of their skills. Since this pioneer study, the temporal organization of the stroke and the inter-arm coordination have been received the attention of the researchers and coaches (cf. Seifert et al., 2010 for a more detailed analysis). Eleven years ago, Chollet et al. (2000) proposed a method to quantify and qualify the inter-arm coordination on front crawl: the Index of Coordination (IdC). This index is based on the duration of the front crawl stroke phases (entry, pull, push and recovery) and measures the lag time between the end of the propulsive phase of one arm and the beginning of the propulsive phase of the other arm. The lag time is expressed as a percentage of the duration of a complete stroke cycle. According to the above referred authors, the IdC value reveals three possible coordination modes in the front crawl: opposition (when continuity between the two arm propulsions is observed, IdC = 0%), catch-up (when a time gap between the two arm propulsions is observed, IdC < 0%) and superposition (when an overlap of the two arm propulsion is observed, IdC > 0%). Seifert et al. (2004a) showed that the preferential inter-arm coordination is related with the pace adopted by the swimmer. In this sense, to slower paces. 1.

(24) (3000m to 200m), the swimmer adopt a catch-up pattern, and to faster paces (from 100m to maximal velocity) they tend to adopt superposition pattern. Although the IdC is described as a distinguish parameter of swimmer‟s ability and technique (Chollet et al., 2000), Seifert et al. (2004b) observed that it increases with the swimming velocity nonetheless the swimmer‟s characteristics or level. According to these authors, the concomitant increase of IdC with velocity is associated with the adaptations that the swimmer makes as a consequence of the change of same factors, such as the drag associated to the velocity increase (Schnitzler et al., 2007). In this sense, changes on arm coordination should be seen as an individual adaptation of the swimmer to a given context. Since the first study conducted by Chollet et al. (2000), other studies have been made on this theme. These studies attempt to understand the importance of the IdC on the performance and its relationship with other relevant parameters to swimming performance. They conclude that arm coordination is influenced by a large group of factors, such as personal „style‟ and gender (Seifert et al., 2004a), stroke rate (Potdevin et al., 2006), race paces and stroke length (Seifert et al., 2007), velocity and expertise (Lerda et al., 2001). The major conclusion of these studies was that the IdC characterize the swimmer‟s biomechanical and coordinative answer to a given velocity or intensity. Thus, arm coordination emerges not as a result of symbolic prescriptions of action patterns but rather as a consequence of the constraints imposed on action (Seifert et al., 2007). According to these last study three types of arm coordination constraints may be considered: (i) the organism constraints, associated with the swimmer, such as gender or body anthropometry; (ii) the environmental constraints, that are external to the organism and couth be manipulated by the experimenter, such the velocity, stroke rate and stroke length effect; and (iii) and the task constraints, that are the task goal or the instructions specifying the response dynamics, such as the pace effect. Additionally to these factors, the influence of other constraints remains unknown. In fact, Alberty et al. (2005) suggested that the metabolic factors may also have a considerable influence over the arm coordination, by relating the intracyclic velocity variations and the IdC in front. 2.

(25) crawl during exhaustive exercise, and observing it was observed that under fatigue conditions the IdC values increases (even when the velocity maintains or decreases). The purpose of this thesis was to characterize, in highly trained swimmers of both genders, coordinative and bioenergetical parameters in front crawl swimming, and the relation between them. It were conducted a number of investigations to understand the above-referred situation, being presented in Chapters 2 and 3, and in Appendix I and II of this thesis. Additionally, a general discussion was elaborated upon the overall results obtained from the above referred studies, and with the reports of the specialized literature (Chapter 4). The main corresponding conclusions are presented on Chapter 5, and some suggestions for future researches on Chapter 6. Firstly, it was conducted a case study (Appendix I) that aimed to relate IdC with energy cost (C) in a national level female swimmer who performed an intermittent incremental protocol, with increments of 0.05m.s-1 for each 200m stage (and 30s intervals) until exhaustion. This protocol was validated before (Cardoso et al., 2003), and was applied to swimmers of both genders (Fernandes et al., 2005), proficiency levels (Fernandes et al., 2006) and children swimmers (Fernandes et al., 2010). In fact, among the bioenergetical parameters, swimming economy is considered a parameter of major interest in the literature (Chatard et al., 1990; Troup et al., 1986; Pendargast et al., 2003) The C of swimming is considered as the total energy expenditure, above pre-exercise resting value, required for displacing the body over a given unit of distance (di Prampero et al., 1986; Pendargast et al., 2003), and is it seen as an important bioenergetical determinant of swimming performance (Costill et al., 1985; Zamparo et al., 2005; Figueiredo et al., 2011). According to Lavoie and Montpetit (1986), the total energy expenditure increases linearly with the velocity, presenting a high correlation. Since water resistance is related to velocity squared (D=k. v2), obviously the increase in the total energy expenditure as the velocity increase traduce the necessity of overcoming a higher water resistance (Holmér, 1974; Holmér et al.,. 3.

(26) 1983; Chatard et al., 1990; Vilas-Boas and Santos, 1994; Alves et al., 1996; Vilas-Boas, 1996). Therefore, energy expenditure (particularly the oxygen consumed (VO2) at a given sub-maximal velocity) is influenced by drag and swimming technique. From this, being the IdC a parameter that characterizes swimmers skills, it should be highly related with C. This pilot study was subsequently extended to a larger group of subjects, being as well used a partial correlation test between these two variables (IdC and C), removing the effect of velocity (Chapter 2). Being well known that velocity is one of the major predictors of IdC changes (Chollet et al., 2000; Seifert et al., 2007), it is expected to observe a parallel increase of IdC and C by the influence of velocity, once it has been proved the increase of the C with the increase of swimming velocity (Fernandes et al., 2005; Fernandes et al., 2006; Barbosa et al., 2008). The question if these two parameters are commonly influenced by velocity and are not significantly intercorrelated when removing the effect of velocity was partially solved in the study presented on Chapter 2, in which it was decided to analyze the partial correlation between the two variables. Thus, in order to answer to the question raised on the study presented on Chapter 2, it was tried to understand the relation between IdC and one of the most related parameters with swimming economy, the intracyclic velocity variation – IVV (cf. Appendix II). The IVV represents the fluctuations of the instantaneous velocity during a stroke cycle that result from the application of forces (resistive and propulsive) acting on the swimmer‟s body (Vilas-Boas, in press). Moreover, the link between IVV and the coordination of propulsive actions is not evident, since IVV reflects the swimmer‟s ability to coordinate propulsive forces (Vilas-Boas, 1996) and its magnitude depends on the combination of both resistive and propulsive forces acting on the swimmers body (Alberty et al., 2005), i. e. two swimmers may thus have the same coordination of propulsive actions but not the same streamline, which would lead to different IVV (Schnitzler et al., 2007). In this sense, the combination of the IdC with the IVV provides information about the effectiveness of the changes on propulsion made by the swimmer. Once the IdC gives temporal information about the management of propulsive actions,. 4.

(27) but provides no information about the intensity of the propulsive forces exerted or the resistive forces that the swimmer encountered. IVV and IdC thus seem to provide complementary information, as IdC gives temporal indications about swimmer‟s ability to coordinate their propulsive action whereas IVV gives kinetic indications about the consequences of propulsive and resistive force combinations. Thus, it was tried to understand how IdC is related with IVV and how this relation is reflected on C. Since the incremental and intermittent test employed is conducted until voluntary exhaustion, it was hypothesized that the effect of the accumulated fatigue, during a time limit test at minimum velocity that elicits the maximal oxygen consumption (vVO2max), tends to lead swimmers to increase their arm coordination in order to do not compromise swimming velocity. This fact is showed by the increase on the duration of the propulsive phases and the decrease of the propulsive phases values, and it should associated to less velocity fluctuation, even if this situation implies an increase in C. In Chapter 3, a new experimental study is presented. This work aimed to verify if there is a critical point on the relation between IdC and velocity related with the individual anaerobic threshold (AnTind). The AnTind represent the intensity above which it is observed an exponential increase in blood lactate concentrations ([La-]), and has been considered as a topic of great interest in swimming literature (Bonifazi et al., 1993; Costill et al., 1992; Kelly et al., 1992; McLellan and Cheung, 1992; Olbrecht 2000; Anderson et al., 2006). This parameter is used on performance prediction, in assessment of aerobic capacity, in swimming training intensities prescription, and in exercise intensity control (Denadai et al, 2000; Wakayoshi et al., 1992). The results from the most recent studies (Gastin, 2001; Rodriguez and Mader, 2003; Figueiredo et al., 2011) also stress out the importance of the aerobic metabolism on total energetic required for almost all the competitive exercise duration in swimming events. According to these previous findings, training at the intensity correspondent to AnTind consists on an important physiological goal in swimming training, in order to develop the swimmer‟s aerobic capacity (Rodriguez and Mader, 2003). Furthermore, the intensity associated to AnTind,. 5.

(28) represents not only a physiological transition, but also a biomechanical boundary. In fact, some studies have evidenced an intensity of exercise beyond which the stroke parameters become compromised (Keskinen and Komi, 1988; 1993; Wakayoshi et al., 1996; Dekerle et al., 2002; Dekerle et al., 2005), corroborating the findings of Weiss et al. (1988), that observed a relation between blood lactate accumulations and changes on stroke parameters. Although non study had been made in order to understand the relation between arm coordination and the AnT, but knowing that IdC is highly related with stroke rate and stroke length (Potdevin et al., 2006; Seifert et al., 2007a), and knowing as well that IdC does not have a linear increase with the velocity increase (Seifert et al., 2004a; Seifert et al., 2007a), it is expectable their relation. In the study presented on Chapter 3, we try to understand the relation between all these parameters (Stroke Rate, Stroke Length, IdC and AnTind). Being swimming a complex modality in which biomechanical and bioenergetic factors are inter-related, and inter-dependent, it is of great importance to understand the adaptations of the technical skill to the constraints imposed by the increase of the intensity. The present thesis pretends to go in this direction, trying to comprehend the interaction between these two domains, the bioenergetical, which is responsible to provide the energy required by the biological system to perform the swimming skill, and the biomechanical, responsible by the form that energy is converted in mechanical work.. 6.

(29) CHAPTER 2 RELATIONSHIP BETWEEN ARM COORDINATION AND ENERGY COST IN FRONT CRAWL SWIMMING. Morais, P.1 ; Keskinen, K.L.2 ; Seifert, L.3 ; Chollet, D.3 ; Vilas-Boas, J.P.1 ; Fernandes, R.J.1. 1University of Porto, Faculty of Sport, Cifi2d, Portugal 2 Finnish Society of Sport Sciences, Finland 3 University of Rouen, Faculty of Sport Sciences France. Proceedings of the XIth International Symposium for Biomechanics and Medicine in Swimming. Norwegian School of Sport Science, pp. 74-76.. 7.

(30) Abstract The aim of the study was to assess the relationship between the Index of Coordination (IdC) and the Energy Cost of exercise (C) in front crawl swimming. Seven high level swimmers performed a paced intermittent incremental protocol of 7 × 200m (0.05m.s-1 increments, 30s intervals), until maximal oxygen consumption intensities. IdC was assessed as the time gap between the propulsion of the two arms. Oxygen consumption was measured through direct breath by breath oximetry and lactate analyses were conducted at rest, in the intervals and at the end of exercise. Along the protocol, concomitant with the velocity raise, both C and IdC increased (r=0.98 and r=0.99, p<0.01, respectively). A very high relationship was also observed between IdC and C (r=0.99, p<0.01). However, when removing the effect of velocity, the relationship between IdC and C was not significant.. Key words: elite swimmers, energy cost, index of coordination. Introduction Performance in swimming is measured by the time that the swimmer needs to cover a specific distance. The capacity to reach and maintain a given velocity is highly dependent on biomechanical and physiological parameters. Among the biomechanical factors, the influence of the stroking parameters (stroke rate and stroke length) on swimming performance is well reported in the literature (Keskinen et al., 1993; Wakayoshi et al, 1995). Furthermore, it was shown that the temporal organization of the stroke is also important to characterise highly skilled performance swimmers (Chatard et al., 1990). More recently, attention has been given to these modifications on temporal organisation of arm stroke phases and arm coordination, assessed by the Index of Coordination (IdC), initially proposed by Chollet et al. (2000). The IdC in front crawl is based on the lag time between the propulsive phases of each arm, which quantifies three possible coordination modes (Chollet et al., 2000): opposition (continuity between two arm propulsions, IdC = 0%), catch-up (a time gap between the two. 8.

(31) arm propulsions, IdC < 0%) and superposition (an overlap of the two arm propulsions, IdC > 0%). According to Seifert et al. (2007), the arm coordination in swimming is influenced by some constraints: environmental constraints (e.g. active drag and velocity), task constraints (pace imposed, goal, instructions or rule of the task) and organism constraints (the swimmer speciality, anthropometric characteristics and gender). In addition to these constraints, it is also hypothesized that physiological parameters could influence the arm coordination in front crawl, being IdC sensitive to metabolic fatigue (Alberty et al., 2005). Thus, an increase in the IdC values seems not to be exclusively linked to an increase in velocity or to the above-referred factors. In fact, it is admissible that other parameters could explain the raise of the IdC values concomitant with the increase of swimming intensity (such as some physiological parameters). The idea that, physiological parameters could influence coordinative and biomechanical parameters (and vice-versa), has already been suggested, i.e. swimming economy is highly correlated with biomechanical parameters (Chatard et al., 1990; Vilas- Boas, 1996). More recently, it was also reported that the stroke mechanics are highly correlated with the energy cost of exercise (C) (Barbosa et al, 2008), a parameter generally used to quantify swimming economy. The assessment of the C in swimming is well reported in the literature since the 1970s, and is considered as the total energy expenditure required for displacing the body over a given unit of distance (Zamparo et al, 2005). Furthermore, it is accepted as an important bioenergetical determinant of swimming performance (Wakayoshi et al, 1995; Kjendlie et al., 2004; Fernandes et al., 2006). However, the body of scientific literature needs approaches on the relationships between the IdC and the C in trying to understand how these two variables may be connected. The present study aimed at assessing relationships between the IdC and the C in front crawl, especially at intensities ranging between 70% and 100% of the maximal oxygen consumption (V O2max). We hypothesised that if velocity is controlled, IdC and C are inversely related.. 9.

(32) Methods Seven high-level swimmers (17.0 ± 1.8 years; 168.0 ± 8.8cm; 58.4 ± 8.2kg) participant in national swimming championships were tested. Mean (± SD) main physiological characteristics were: 18.0 (6.9) % of fat mass, 54.9 (10.1) ml.kg1. .min-1. O2max and 7.5 (2.4) of blood lactate concentrations ([La-]) at 2max.. In an indoor 25 m swimming pool, the. participants performed an intermittent incremental protocol, with increments of 0.05m.s-1 each 200m stage (and 30s intervals), until exhaustion (Fernandes et al., 2003). Initial velocity was established according to the individual level of fitness and was set at the swimmer‟s individual performance on the 400m freestyle minus seven increments of velocity. Swimming velocity was controlled using a visual pacer (TAR 1.1, GBK-electronics, Aveiro, Portugal) with successive flashing lights, 2.5 m apart, on the bottom of the pool.. O2 was. measured through direct breath-by-breath oximetry (K4 b2, Cosmed, Rome, Italy) connected to the swimmer by a respiratory snorkel and valve system (Keskinen et al., 2003). Capillary blood samples (25 μl) for [La -] analysis were collected from the earlobe at rest, in the 30s rest interval, at the end of exercise and during the recovery period (YSI1500LSport auto-analyser, Yellow Springs Incorporated, Ohio, USA). The C was calculated by dividing total energy expenditure (Ė) by velocity (v) and converted to SI units, were 1 mlO2 is equivalent to 20.1 J (Zamparo et al., 2005; Fernandes et al., 2006):. C = Ė /v (1). 2. net (difference. between the value measured in the end of the stage and the rest value), and the blood lactate net (difference between the value measured in two 2. kg-1. mmol-1 proportionality constant and by Equation (2) (cf. Fernandes et al., 2006). 10.

(33) Ė=V. O2net + [La-]net (2). Two video cameras (JVC GR-SX1 SVHS and JVC GR-SXM 25 SVHS) were fixed on the lateral wall of the pool at a 10m distance perpendicular to the swimmers‟ plane of movement. The cameras were connected to a double entry and edited on a mixing table (Panasonic Digital Mixer WJ-AVE55 VHS), providing a dual-media image (Panasonic AG 7355), below and above the water surface (Vilas-Boas et al., 1996), at a frequency of 50 Hz (1:250/s shutter speed). For each step of the incremental protocol, two arm strokes were analysed in every 50m of the 200m. Arm stroking coordination was obtained through IdC (Chollet et al., 2000), being each arm stroke broken down into four phases: (i) entry and catch (corresponding to the time between the entry of the hand into the water and the beginning of its backward movement); (ii) pull (corresponding to the time between the beginning of the hand‟s backward movement and its arrival in a vertical plane to the shoulder); (iii) push (corresponding to the time from the position of the hand below the shoulder to its release from the water) and (iv) recovery(corresponding to the point of water release to water re-entry of the arm, i.e., the above water phase). The duration of each phase was measured for each arm-stroke cycle with a precision of 0.02s. The duration of the propulsive phases was the addition of the pull and the push phases, and the duration of the non-propulsive phases was obtained by the sum of the catch and the recovery phases (the duration of a complete arm-stroke was the sum of the propulsive and non-propulsive phases). The IdC was calculated as the time gap between the propulsion of the two arms as a percentage of the duration of the complete arm stroke cycle. Higher negative percentage values expressed an evident discontinuity in the inter-arm propulsion, tending to IdC=0% as the time gap was diminishing. Mean ± SD computations for descriptive analysis were obtained in each stage for all variables (all data were checked for distribution normality with the. 11.

(34) Shapiro-Wilk test). Pearson correlation coefficient and partial correlation were applied. Level of significance was established at 5%.. Results The mean ±. O2max, C, and IdC, obtained in each. step during the intermittent incremental test, are presented in Table 1. An increase of swimming intensity implies an increase of both C and IdC (Table 1).. Table 1. O2max, IdC and C obtained in each 200m step of the. incremental protocol (n=7). Step. v (m.s ).  O2max (%) V. C (J.kg .m ). IdC (%). 1. 1.15 ± 0.1. 72.1 ± 8.7. 9.4 ± 2.5. -12.5 ± 2.5. 2. 1.20 ± 0.1. 76.5 ± 9.1. 10.3 ± 2.8. -12.1 ± 2.7. 3. 1.25 ± 0.1. 77.8 ± 5.3. 10.1 ± 3.0. -11.8 ± 2.6. 4. 1.30 ± 0.1. 85.5 ± 3.3. 11.5 ± 3.2. -10.9 ± 2.6. 5. 1.35 ± 0.1. 90.9 ± 3.2. 12.7 ± 2.8. -9.7 ± 2.7. 6. 1.40 ± 0.1. 97.3 ± 3.2. 13.7 ± 2.4. -8.2 ± 2.7. 7. 1.45 ± 0.1. 100.0 ± 0.0. 14.0 ± 4.2. -6.8 ± 2.5. -1. -1. -1. The relationships between velocity and C, and velocity and IdC are shown in Fig. 1 (left panel), being possible to observe a high correlation value between these variables (r=0.98 and r=0.99, respectively, both for p<0.01). A strong relationship exists also between IdC and C (r=0.99, p<0.01, Fig. 1, right panel). However, when removing the effect of velocity (using partial correlation test), the relationship between IdC and C was not significant (r=0.42, p=0.40).. 12.

(35) Figure 1. Direct relationships between velocity and IdC, and velocity and C (upper panel), and between IdC and C (lower panel) for the total group of swimmers. Linear and polynomial regression equations and correlation values are indicated.. Discussion Despite a previous case study by Morais et al. (2008), and a study that was conducted with sprint swimmers performing at incremental sub-maximal intensities (Komar et al., 2010), the present study is the first that aimed to relate IdC and C in front crawl. The present results agree with both the referred studies, finding positive and significant r values between both variables. In this study, however, it was confirmed that this is true for velocity values ranging from very low t. O2max). All swimmers reached their. maximal aerobic power during the incremental protocol, which was assured by traditional physiological criteria (cf. Fernandes et al., 2003). Subjects presented O2max mean values similar to those described in the literature for experienced competitive swimmers (Wakayoshi et al, 1995; Rodriguez and Mader, 2003; Fernandes et al., 2006). The obtained mean values of [La -]max are in accordance with the literature for intensities of exercise corresponding to. 13.

(36) O2max (Fernandes et al., 2003; Rodriguez and Mader, 2003; Fernandes et al., 2006). Along the incremental protocol it was observed that an increase in the swimming intensity led to an increase of the IdC. This is consistent with previous studies that showed a raise of IdC values with increasing race paces, namely from 1500/800 to 50 m freestyle (Chollet et al., 2000; Seifert et al., 2004; Seifert et al., 2007). This increase seems to be a strategy that swimmers use to overcome higher active drag that is related with higher swimming velocity (Seifert et al., 2004). These data also reveals that swimmers changed their arm stroke coordination, from moderate to heavy exercise intensities, in order to be able to reach higher swimming velocity. In fact, this shift in IdC from a catch-up pattern to a pattern closer to the opposition coordination mode, aiming to achieve hig. O2max swimming intensity, was also. described before (Chollet et al., 2000; Seifert et al., 2004; Seifert et al., 2007). The values of IdC obtained in the present study were similar to those obtained in the previously mentioned studies and it did not reach positive values since IdC>0% only occurs after 93% of the swimmers maximal velocity, which corresponds to the 100 m maximal velocity (Seifert et al., 2004). Such as the IdC, the C values also increased with velocity. This fact has been described before for front crawl stroke with similar C values (Zamparo et al., 2005; Morais et al., 2008; Komar et al, 2010), and seems to be justified by the increasing power output (P = Dv) necessary to overcome drag (D), and presumably by the increase in internal work associated with a higher stroke rate. The main finding of this study was the very high direct relationship between IdC and C, which is, as stated, in accordance with previous studies in swimming, but also in human terrestrial locomotion, namely in the walk-run transition (cf. Seifert et al., 2007). Studies have been carried out in order to relate the C with other biomechanical parameters. Barbosa et al. (2008) showed that the C is highly related to stroke parameters, namely with stroke rate and stroke length, while Chatard et al. (1990) showed that C is dependent on swimming. 14.

(37) technique. In this sense, after observing that the IdC, a coordinative parameter, is strongly related with C, our results seems to be consistent with literature (Alberty et al., 2005), indicating that the mode of coordination might be an individual response to physiological constraints associated to the task. However, despite the agreement of the results of other approaches, the simple analysis of the r value obtained between IdC and C shows that the C increase with the increased continuity of technique (higher IdC), which seems to be paradoxal, being probably explainable by the fact that both parameters are strongly influenced by velocity (as shown in fig. 1). In accordance, we decided to analyse the partial correlation of the two variables removing the effect of velocity. Surprisingly, IdC and C did not correlate significantly (r=0.42, p=0.40). Furthermore, the obtained r value remains positive, while it was theoretically expected a negative relationship. Indeed, we hypothesised that, controlling the velocity effect, the reduction of propulsive discontinuities should allow the front crawl technique to become more economical, instead of implying higher energy costs. Samples with higher number of subjects as well as other factors (e.g. intracyclic velocity variation) should be searched to explain these apparently conflicting findings. Particularly, we recommend to study IdC and C at the same swimming velocity performed in different subjects, and in the same subjects manipulating coordination.. 15.

(38)

(39) CHAPTER 3 ARM. COORDINATION, STROKE PARAMETERS AND ANAEROBIC THRESHOLD. ASSESSMENT IN FRONT CRAWL SWIMMING. Morais, P.1; Figueiredo, P.1; Marques-Aleixo, I.1; Vilas-Boas, J.P.1, 2; Fernandes, R.J.1, 2. 1 University of Porto, Faculty of Sport, Portugal 2 CIFID2D. Submitted for publication. 17.

(40) Abstract The purpose of the present study was two-fold: (i) to analyse the behaviour of index of coordination in front crawl swimming, observing the eventual existence of an inflexion point on the relation between index of coordination and velocity and (ii) to observe if the eventual index of coordination inflexion point is coincident with the individual anaerobic threshold, and with changes in stroke rate and stroke length. Eleven high level swimmers performed a paced intermittent incremental protocol of 7 × 200m (0.05m.s-1 increments, 30s intervals). It was observed that index of coordination does not increase linearly with swimming velocity, and a critical point was observed. The intensity at was observed this non-linear increase is highly related (r=0.82, p<001) with the intensity associated with the individual anaerobic threshold as with significant changes on stroke rate and a stroke length (r=0.79, p<0.01; r=0.74, p<0.01). These findings seem to confirm that anaerobic threshold could induce changes in stroke organization and suggest that changes on arm coordination could be connected to physiological changes.. Introduction The study of the coordination between arm movements in front crawl is a major area of interest in today‟s swimming related literature (Seifert et al., 2010). The investigation of the changes in inter-arm coordination mode has been assessed by the index of coordination proposed by Chollet et al. (2000) and, since this pioneer work, several studies have been developed trying to understand the relationship between inter-arm coordination and other swimming performance related parameters. In fact, it was observed that coordination depends on a large number of factors, in accordance with the three types of constraints proposed by Newell (1986) and adapted by Seifert et al. (2007) for swimming: (i) the organism constraints, associated with the swimmer, such as gender or body anthropometry; (ii) the environmental constraints that are external to the organism and could be manipulated by the researcher, such as swimming velocity, stroke rate and stroke length and; (iii) the task constraints, particularly. 18.

(41) the task goal or the instructions specifying the response dynamics, such as the pace effect. More recently it was observed that inter-arm coordination in front crawl also might be linked with physiological parameters, such as the energy cost (Fernandes et al., 2010a; Seifert et al., 2010), confirming that coordinative parameters are related with the physiological ones, as previously demonstrated with stroking parameters (Keskinen et al., 1988; Wakayoshi et al., 1996; Dekerle et al., 2002; Dekerle et al., 2005). In the bioenergetical spectrum, the anaerobic threshold is one of the most studied parameters, being well related to swimming performance (McLellan and Cheung, 1992; Fernandes et al., 2010b). Moreover, it seems also able to influence the behaviour of the biomechanical parameters, being reported concomitant changes on some selected biomechanical parameters and blood lactate concentrations ([La-]) during incremental and constant load tests, evidencing that, technical changes could be related to metabolic modifications (Weiss et al., 1988; Keskinen et al., 1993; Wakayoshi et al., 1996). Indeed, the anaerobic threshold seems to represent not only a physiological transition but also a biomechanical boundary, and several studies reported a stroke length drop and a change on stroke rate behaviour coincident with the anaerobic threshold intensity (Keskinen et al., 1988; Keskinen et al., 1993; Dekerle et al., 2005). Knowing that index of coordination is positively related with the stroke rate (Potdevin et al., 2006) and negatively with the stroke length (Seifert el al., 2007), it is expected that the index of coordination presents a significant change coincident with the swimming intensity corresponding to the anaerobic threshold. In fact, Seifert et al. (2007) observed that index of coordination does not increase linearly with velocity when studied race paces from 3000m to maximal velocity, in front crawl. These authors found a non-linear adaptation in arm coordination and a critical point on index of coordination behaviour was observed at the intensity corresponding to the 200m race pace. These nonlinear adaptations on inter-arm coordination emerged when non-specific control parameters changed, from the interaction with various constraints, which act as stable attractors (Seifert et al., 2007).. 19.

(42) The purpose of the present study is two-fold: (i) to analyse the behaviour of index of coordination along a traditionally used intermittent incremental swimming protocol, observing the eventual existence of an inflexion point on the relation between index of coordination and velocity and (ii) to observe if the eventual index of coordination inflexion point is coincident with the individual anaerobic threshold, and with changes in stroke rate and stroke length. Understanding the index of coordination modifications through an intermittent incremental swimming protocol could provide information on swimmer‟s motor control that could help researchers and coaches to better detect the optimal pattern for a given intensity, and to diagnosis arm coordination changes along the training process.. Methods. Participants Eleven highly trained swimmers (5 males and 6 females) of 19.5 ± 0.7 and 17.0 ± 1.5 years old, 72.8 ± 14.4 and 58.4 ± 3.2kg of body mass, 180.0 ± 17.0 and 165.0 ± 3.2cm of height, and 5.0 ± 1.4 and 20.0 ± 2.2% of fat mass (respectively for males and females) volunteered to participate in the present study.. Swim Trials In a 25m indoor swimming pool, swimmers performed an intermittent incremental protocol, with increments of 0.05m.s-1 each 200m stage (and 30s intervals), until exhaustion (Fernandes et al., 2003). Initial v was established according to the individual level of fitness and was set at the swimmer‟s individual performance on the 400m freestyle event, minus seven increments of v. V was controlled using a visual pacer (TAR 1.1, GBK-electronics, Aveiro, Portugal) with successive flashing lights, 2.5m apart, on the bottom of the pool.. 20.

(43) Physiological Data Collection In the intermittent incremental protocol [La-] were assessed from blood samples collected from the ear lobe, at rest, during the 30s, and 1, 3, 5 and 7min after the end of the protocol (YSI1500LSport Auto-analyser, Yellow Springs, Inc., Yellow Springs, OH, USA).. Video Analysis Two synchronized video cameras (JVC GR-SX1 SVHS e JVC GR-SXM 25 SVHS), both fixed on the lateral wall of the pool at 10m of the swimmer line of movement and with the optical axis perpendicular to the swimmers‟ displacement direction, were used. The cameras were connected to a double entry audiovisual mixer (Panasonic AG 7355) and edited on a mixed table (Panasonic Digital Mixer WJ-AVE55 VHS), giving a double projection, up and above the water surface (Vilas-Boas, 1996).. Arm Movement Coordination Two arm strokes were analysed at every 50m of each 200m step, totalizing eight arm strokes. Arm stroke coordination was obtained through index of coordination (following the methodology proposed by Chollet et al., 2000). Each arm stroke was broken down into four phases: (i) entry and catch of the hand in the water, corresponding to the time between the entry of the and into the water and the beginning of its backward movement; (ii) pull phase, corresponding to the time between the beginning of the hand‟s backward movement and its arrival in a plane vertical to the shoulder; (iii) push phase, corresponding to the time from the position of the hand below the shoulder to its release from the water and; (iv) recovery phase corresponding to the point of water release to water re-entry of the arm, i.e., the above water phase. The duration of each phase was measured for each arm-stroke cycle with a precision of 0.02s.The duration of the propulsive phase was the sum of the pull and the push phases, and the duration of the non-propulsive phase was the. 21.

(44) sum of the catch and the recovery phases. The duration of a complete armstroke was the sum of the propulsive and non-propulsive phases. The index of coordination represented the time gap between the propulsion of the two arms as a percentage of the duration of the complete front crawl arm stroke cycle.. Stroke Parameters As in the inter-arm coordination assessment, two arm strokes were analysed at every 50m of the 200m step totalling eight arm strokes for stage. From the duration of each stroke, measured with the precision of 0.02s, was obtained the stroke rate, and the distance per cycle or stroke length was calculated from velocity vs. stroke rate ratio.. Determination of individual anaerobic threshold, index of coordination and stroke rate inflexion point and stroke length drop point From the assessed [La-], index of coordination, stroke rate and stroke length it were determined the exact point for the beginning of an exponential rise/drop of these parameters. This was accomplished by the [La-] (and index of coordination, stroke rate, stroke length) vs. velocity curve modelling method using a pair of regression lines (one linear and other exponential), as proposed before for the metabolic anaerobic threshold assessment (cf. Machado et al., 2006; Fernandes et al., 2010b). An illustration of this methodology is displayed in Figure 1. Anaerobic threshold was assumed to be the interception point, at the maximal fit situation, of a combined pair of regressions, being possible to determine the exact point for the beginning of an [La -] exponential rise. The same procedure was performed for index of coordination/velocity, stroke rate/velocity and stroke length/velocity (Figure 1) in order to examine if there is any non-linear increase on the relation between arm coordination, stroke rate and stroke length, and velocity to the studied intensities.. 22.

(45) -. Figure 1. Determinations of inflexion/drop point of blood lactate concentrations [La ] commonly defined as the individual anaerobic threshold (AnT ind) index of coordination (IdCinflex), stroke rate (SRinflex), and stroke length (SLdrop), from the relation between these parameters and swimming velocity.. Data Analysis Mean and standard deviation computations for descriptive analysis were obtained for all variables (all data were checked for distribution normality with the Shapiro-Wilk test). Pearson‟s correlation coefficient and t-test were also used. A significance level of 5% was accepted.. Results Values of means and standard deviations for swimming velocity, [La -], index of coordination, stroke rate and stroke length obtained in the incremental intermittent protocol are presented in Table 1. It is possible to observe an. 23.

(46) increase of [La-], index of coordination and stroke rate, and a decrease of stroke length values concomitant with the increase of the steps velocities.. Table 1. Means and standard deviations for swimming velocity, index of coordination, stroke -. rate, stroke length and [La ] for n=11.. Stage. Index of. Swimming -1. velocity (m.s ). coordination (%). Stroke rate. Stroke length. -1. -1. (cycles. min ). (m.cycle ). -. -1. [La ] (mmol.l ). 1. 1.27 ± 0.08. -12.50 ± 2.44. 27.78 ± 0.98. 2.68 ± 0.15. 2.13 ± 1.20. 2. 1.32 ± 0.07. -12.11 ± 2.59. 28.85 ± 1.27. 2.64 ± 0.15. 2.19 ± 1.07. 3. 1.35 ± 0.07. -11.76 ± 2.52. 29.70 ± 1.50. 2.54 ± 0.17. 2.26 ± 1.16. 4. 1.42 ± 0.08. -10.86 ± 2.47. 30.93 ± 1.39. 2.53 ± 0.16. 2.55 ± 1.39. 5. 1.45 ± 0.07. -9.74 ± 2.30. 32.26 ± 1.68. 2.49 ± 0.16. 3.33 ± 1.60. 6. 1.49 ± 0.07. -8.19 ± 2.46. 33.71 ± 1.49. 2.48 ± 0.16. 5.45 ± 2.07. 7. 1.54 ± 0.09. -6.95 ± 2.32. 35.29 ± 1.86. 2.45 ± 0.17. 7.90 ± 2.40. Data concerning the variables obtained in the incremental test: [La -] at rest, maximal [La-], [La-] corresponding to the individual anaerobic threshold, index of coordination inflexion point (IdCinflex), stroke rate inflexion point (SRinflex), stroke length drop point (SLdrop), and the corresponding velocities to these parameters phenomena are reported in Table 2, for total sample and by gender groups.. 24.

(47) -. -. -. Table 2. Mean and standard deviation values for [La ] at rest, maximal [La ], [La ] corresponding to the individual anaerobic threshold, index of coordination value corresponding to the IdCinflex, stroke rate value corresponding to the SRinflex, stroke length value corresponding to SLdrop, and the corresponding velocities to this phenomena, for total sample and both genders. Men. Women. Total Sample. (n=5). (n=6). (n=11). 0.72 ± 0.15. 0.73 ± 0.10. 0.72 ± 0.12. 8.73 ± 1.73. 10.59 ± 2.57. 8.87 ± 2.05. 3.51 ± 0.66. 3.32 ± 0.21. 3.45 ± 0.51. 1.38 ± 0.05. 1.31 ± 0.04. 1.33 ± 0.07. -11.06 ± 3.21. -10.17 ± 2.24. -10.19 ± 2.97. 1.38 ± 0.06. 1.33 ± 0.01. 1.34 ± 0.05. 29.79 ± 2.26. 30.65 ± 1.70. 30.50 ± 1.93. 1.37 ± 0.04. 1.33 ± 0.07. 1.36 ± 0.06. -1. 2.75 ± 0.21. 2.49 ± 0.07. 2.52 ± 0.19. v SLdrop (m.s ) *. 1.38 ± 0.05. 1.34 ± 0.03. 1.36 ± 0.05. -. l-1. [La ]rest (mmol. ) -. -1. [La ]max (mmol.l ) -1. AnTind (mmol.l ) -1. v AnTind (m.s ) ** IdCinflex (%) -1. v IdCinflex (m.s ) * -1. SRinflex (cycles.min ) -1. v SRinflex (m.s ) * SLdrop (m.cycle ) -1. ** p < 0.01; * p < 0.05 significant differences between gender groups -. Blood lactate concentrations at rest - [La ]rest; Maximal blood lactate concentrations obtained -. during the test - [La ]max; Blood lactate concentrations corresponding to the individual anaerobic threshold - AnTind; Swimming velocity corresponding to the individual anaerobic threshold - v AnTind; Index of coordination value at we assist to an inflexion point on the relation between the index of coordination and swimming velocity - IdCinflex; Swimming velocity corresponding to the index of coordination inflexion point - v IdCinflex; Stroke rate value at we assist to an inflexion point on the relation between the stroke rate and swimming velocity - SRinflex; Swimming velocity corresponding to the stroke rate inflexion point - v SRinflex; Stroke length value at we assist to an drop point on the relation between the stroke length and swimming velocity - SLdrop; Swimming velocity corresponding to the stroke length drop point - v SLdrop.. In addition to the statistical differences observed between gender groups, it seem important to highlight that no significant differences between the velocity corresponding to the IdCinflex, AnTind, SRinflex and SLdrop, were observed; on the. 25.

(48) contrary it was observed high and significant relationships between all the velocities associated to the critical points, as expressed in Table 3 that shows a correlation matrix between the velocities of IdCinflex, AnTind, SRinflex and SLdrop.. Table 3. Correlation matrix between the velocity of the index of coordination inflexion point, individual anaerobic threshold, stroke rate inflexion point and stroke length drop point. V IdCinflex. v AnTind. v SRinflex. v IdCinflex. -. v AnTind. 0.82**. -. v SRinflex. 0.79**. 0.91**. -. v SLdrop. 0.74**. 0.80**. 0.62*. v SLdrop. -. ** p < 0.01; * p < 0.05 Swimming velocity corresponding to the index of coordination inflexion point - v IdCinflex; Swimming velocity corresponding to the individual anaerobic threshold - v AnTind; Swimming velocity corresponding to the stroke rate inflexion point - v SRinflex; Stroke length; Swimming velocity corresponding to the stroke length drop point - v SLdrop.. Discussion To achieve a certain velocity, swimmers adopt an individual inter-limb coordination (Seifert and Chollet, 2009) with a concomitant individual ratio between stroke rate and stroke length (Craig et al., 1985; Pendergast et al., 2006), supported and/or influenced by bioenergetical variables, such as lactate production and degradation, oxygen consumption and heart rate variability (di Prampero et al., 2008). The present study was conducted at moderate and heavy intensities domains, where it was possible to observe this interplay. Regarding the inter-arm coordination, the observed increase of the IdC with the swimming velocity is in accordance with the literature regarding non-fatigue exercises, although maintaining a catch-up pattern (IdC<0%) during the whole. 26.

(49) test (Chollet et al., 2000; Seifert et al., 2007; Schnitzler et al., 2007; Strzala et al., 2007; Seifert et al., 2010). The modifications on stroke parameters (increase of stroke rate and decrease of stroke length) with velocity were also observed, in accordance with (Craig et al., 1985; Dekerle et al., 2005) suggesting the relationship between stroke parameters and arm coordination referred before (Seifert and Chollet, 2009). In addiction it was also observed the increase in [La ] with the increase of velocity, in line with related literature that reports an increase on energy expenditure with the increasing of velocity (Pendergast et al., 2003), in order to achieve or maintain a certain velocity. High velocities request a higher participation of the anaerobic system on the energy supply, leading to an increase on [La-] (Brooks et al., 2000). Another main finding of the present study was that the observed changes on inter-arm coordination, stroke parameters and [La-] with the velocity increase are not strictly linear at the studied swimming intensities, and a critical point was identified for all these parameters. Regarding the index of coordination sudden increase was already reported by Seifert et al. (2007), but for higher velocities at 200m pace. These authors stated that at this pace, swimmers changed suddenly their arm coordination increasing the index of coordination value, being this non-linear increase understudied as a transition between heavy and sever swimming paces. In our study the intensity at which transition occurred could be interpreted as a threshold between two different paces: the moderate and heavy swim paces. According Seifert et al. (2004) skilled swimming is inherently rhythmical and stable, although flexible modes of coordination between the arms emerge from the interaction between the mechanical properties of the water and the intrinsic dynamics of the body. Therefore, the increase on index of coordination value might be seen as an individual response of the swimmer to the constraints imposed by a particular task (Seifert et al., 2007), and reflects the intensity that the task is performed. Concerning stroke parameters, it was also observed that at a specific point the stroke rate increased and the stroke length decreased in a non-linear way. Similar results were found by Dekerle et al. (2002; 2005), which were linked to changes on blood lactate kinetics during incremental exercise. According these. 27.

(50) authors, when a specific task calls for endurance capacity the reduction of stroke length and the increase of stroke rate, becomes progressively greater. The results of our study highlight that the energy requirements seem to influence the biomechanical characteristics of stroking while swimming at the referred intensities (Weiss et al., 1988; Keskinen et al, 1988; Keskinen et al., 1993; Lepers et al., 2000). Data concerning the [La-], it was observed an inflexion point on blood lactate kinetics, frequently used to identify the individual anaerobic threshold intensity (Kinderman et al., 1979; Brooks et al., 2000; Machado et al., 2006; Fernandes et al., 2010b), being the obtained values in accordance with the ones found by Beneke (1995) and Wakayoshi et al. (1992). Afterwards, analysing the changes of arm coordination, stroke parameters and [La-] along the incremental intermittent protocol, it was observed a high and significant correlation between: the velocity corresponding to the individual anaerobic threshold and the velocity associated with IdCinflex, SRinflex, and SLdrop; the velocity associated with IdCinflex and SRinflex, and SLdrop; and lastly between the velocities associated with SRinflex, and the SLdrop (cf. Table 3). Furthermore, it was also observed that the velocities associated to the above referred phenomena, are quite similar, and no significant differences were obtained between them. The observed relation between stroke parameters and the anaerobic threshold seem to be in accordance with the studies conducted on this thematic (Dekerle et al., 2004; Dekerle et al., 2005), which have underlined similar changes up on the [La-] dynamics and the evolution of the stroking parameters, when the individual anaerobic threshold is reached. Swimmers can keep a low level of stroke rate and a high level of stroke length values throughout exercise performed at slow and predominantly aerobic velocities. However, when the intensity reaches the individual anaerobic threshold, the increase in stroke rate and the reduction in stroke length becomes progressively greater, as also been demonstrated by Keskinen et al. (1993), Dekerle et al. (2002) and Dekerle et al. (2005). Actually is commonly accepted that the anaerobic threshold intensity. 28.

(51) represents not only a physiological, but also a biomechanical boundary, where changes on [La-] are linked with changes on technical parameters (Craig et al., 1985; Weiss et al., 1988; Keskinen et al., 1993; Wakayoshi et al., 1996, Dekerle et al., 2002; Dekerle et al., 2005). To our knowledge no study was carried out to verify if changes on inter-arm coordination and changes on [La-] are connected, changes on arm coordination in aerobic exercise, provoked by modifications on physiological variables, have already been observed (Strzala et al., 2007; Alberty et al., 2009). These modifications on arm coordination can be better explained when regarding the relation between the stroke parameters and arm coordination. After the pioneer study conducted by Cholet et al. (2000), many others studies (Seifert et al., 2004; Schnitzler et al., 2007) had pointed out that the increase of index of coordination values with the velocity increase seem to be connected with the increase of stroke rate, and the decrease of stroke length. According Schnitzler et al. (2007) changes on index of coordination values reflect changes on the relative duration of the arm propulsion (the push phase in particular) and on the relative duration of the non-propulsive phase (the catch phase in particular) that leads to changes on stroke rate and stroke length (Keskinen et al., 1993; Chollet et al., 2000; Potdevin et al., 2006; Seifert et al., 2007). According to Alberty et al. (2009) this modifications on arm coordination and stroke parameters might be interpreted has a response of the swimmer to achieve a certain velocity, minimising the effects of the drag force increase, resultant of the velocity increase. Thus our results seem to highlight the relation between arm coordination and the stroke parameters, and the influence of the physiological parameters over them, although the inverse situation also is acceptable (Barbosa et al., 2010). Furthermore other technical parameters, such stroke rate (Dekerle et al., 2002), stroke length (Dekerle et al., 2005), changes on [La-] also seem to be connected with simultaneous changes on arm coordination. Several. assumptions. in. relation. to. biomechanical,. physiological,. and. neuromuscular parameters have been proposed to explain movement patterns changes at the anaerobic threshold intensity, not only in swimming, but also in. 29.

(52) other cyclic activities, as cycling and running. Indeed, changes in motor unit recruitment, muscle perfusion, grow of the neuromuscular fatigue and local muscle fatigue have mainly been evoked (Vercruyssen et al., 2002; Lepers et al., 2000). Nonetheless the results of our study, and from the literature, the key factors that decide preferred movement patterns, remain a topic of discussion. In fact the energy requirements seem to influence the stroking characteristics at the studied intensities. As suggested by Figueiredo et al. (2009), changes on arm coordination, linked to muscular endurance limitations, appear to be a compensatory mechanism used by swimmers, to obtain the most efficient arm coordination for a particular context. The declined ability to develop the force necessary to overcome the resistance to forward movement, beyond the anaerobic threshold could account for the decrease in stroke length and the concomitant increase in stroke rate, in order to maintain a certain velocity as suggested by Dekerle et al. (2005) and through them the coordination of arm movements. These findings seem to confirm that anaerobic threshold could induce changes in stroke organization and suggest that changes on arm coordination could be connected to physiological changes.. Conclusion It seem that at moderate and heavy paces the relation of the anaerobic threshold and the stroke organization, play an important roll on swimming performance. Furthermore, the stroke parameters, the index of coordination can be a useful criterion to control the technical parameters and the intensity of aerobic training loads at the same time, once it seems to reflect the effects of exercise at anaerobic threshold and the stroke organization. It appears to be a useful tool for coaches and scientists in order to better understand the technique modifications at aerobic exercise, more specifically at the individual anaerobic threshold intensity. Indeed, we can also refer that our results highlight the need to include the index of coordination in the control of aerobic training. Improvements on swimming technique could be achieved, with trials. 30.

(53) that consist in maintaining certain arm coordination with a higher swimming speed, or maintaining the anaerobic threshold velocity with a lower index of coordination value.. ACKNO WLED GEMENTS This study was supported by grant: PTDC/DES/101224/2008 (FCOMP-010124-FEDER-009577). 31.

(54)

(55) CHAPTER 4 GENERAL DISCUSSION. Arm coordination, assessed by the index of coordination (IdC) is a topic of great interest among the scientific swimming community (Chollet et al., 2000; Seifert et al., 2007a; Seifert et al., 2010a; Seifert et al., 2010b), since it has been evidenced its relation with swimming performance. Furthermore, it is well known the importance of the connections established between the coordinative and the physiological parameters in swimming (Craig et al., 1985; Vilas-Boas et al., 1993; Dekerle et al., 2002; Pendargast et al., 2006). However, only recently the relationships between these parameters start to receive the attention on the literature. Some time ago, Alberty et al. (2005) suggested that the metabolic factors could have a considerable influence on arm coordination. In this study, that relates the intracyclic velocity variations (IVV) with the IdC in front crawl swimming during exhaustive exercise, it was observed that under fatigue conditions the IdC values increased even when the velocity was maintained or decreased. In this sense, the increase of the IdC should not be automatically linked to a velocity rise, but viewed as a consequence of all the constrains imposed by the context where the action occurs (Seifert et al., 2007a), and where the physiological variables couth also play a role (Seifert et al., 2010b). In this context, the aim of the present thesis was to study the relationship between the coordinative and physiological parameters of front crawl swimming performed at moderate and heavy intensities. In the different studies that integrate this thesis, we have investigated the relation between arm coordination (assessed by the IdC), and some selected biomechanical parameters (stroke rate, stroke length and IVV), with some of the most relevant physiological factors for swimming performance (energy cost of swimming and the anaerobic threshold).. 33.

(56) The energy cost of swimming (C), a parameter generally used to quantify swimming economy, is seen as an important bioenergetical determinant of swimming performance (Wakayoshi et al., 1995; Kjendlie et al., 2004; Fernandes et al., 2005; Fernandes et al., 2006; Barbosa et al., 2010), being his assessment well reported in swimming literature since the 1970s. Some time ago, Chatard et al. (1990) and Vilas-Boas (1996), and more recently Barbosa et al. (2005), observed that swimming economy is highly related with the biomechanical parameters, suggesting that physiological parameters could influence coordinative and biomechanical parameters (and vice-versa). Indeed, Costill et al. (1985) had already demonstrated the importance of C on stroke technique, and its subsequent influence over the aerobic performance. Therefore, in order to know if arm coordination is significantly related with C, it was accomplished a case study (Appendix I), in which the relationship between these parameters during an incremental intermittent protocol was analyzed, what was confirmed. The results obtained in this case study were lately corroborated by a larger group of swimmers (Chapter 2). The main finding of these studies was that arm coordination varies with the swimming economy, once that IdC and C seems to be highly related. Although no study has been conducted in order to relate the IdC with C, the studies carried out to relate the C with other biomechanical parameters and more specifically with stroke parameters, obtained high correlations between them (Chatard et al., 1990; Vilas-Boas, 1996; Barbosa et al., 2008). Knowing that the IdC is well related with the stroke parameters, once changes on the stroke organization induce modifications on stroke rate and stroke length (Seifert et al., 2004a; Potdevin et al., 2006; Seifert et al., 2007a), the findings of these studies seem to support our results. Since the pioneer study conducted by Chollet et al. (2000), a large number of studies have observed the increase of IdC concomitant with swimming velocity (Millet et al., 2002; Seifert et al., 2004a; Seifert et al., 2007a; Seifert et al., 2007b). It seems that this IdC increase, searching a more continuous arm synchronization, is conducted to increase swimmer‟s propulsive force (Seifert et al., 2004a) in way to achieve a certain velocity. In order to minimise the effects. 34.

(57) of the drag force increase, resultant of the velocity increase (Alberty et al., 2005), but also to maintain the propulsive impulse, and try to limit the velocity loss (Seifert et al., 2004a), swimmers tend to change their stroke organization, that is reflected on the increase of IdC value. In the same way, Fernandes et al. (2005), Fernandes et al. (2006) and Barbosa et al. (2008) have described the increase of the C with the increase of velocity, apparently due the increase of drag forces. The results of our studies corroborate the above referred studies: it was observed that the IdC, as the C, increases with velocity, being our values consistent with the ones described before. However, and despite the agreement of our results with others, this relation between the IdC and the C was theoretically expected, once these parameters seem to be equally influenced by the swimming velocity. In this sense, in Chapter 2, we decided to analyze the partial correlation between these two variables, removing the effect of v. Surprisingly, IdC and C did not correlate significantly. Furthermore, it was obtained a positive r value, while it was expected a negative relationship, once that the C increases with the increase continuity of arm synchronization (higher IdC). Indeed, we hypothesized that, controlling the velocity effect, the reduction of propulsive discontinuities should allow the front crawl technique to become more economical, instead of implying higher C. In order to better understand these apparent conflicting findings, we have tried to understand (Appendix II) the relation between IdC and IVV, once IVV, and its relation with the IdC (Alberty et al., 2005; Schnitzler et al., 2007) can be seen as a swimming efficiency indicator. Previous results available in literature support the hypothesis that IVV should be taken as an indicator of the C of locomotion, being inversely related to swimming economy (Fujishima and Miyashita, 1998) and to the maximal velocity attainable by a given swimming technique (Vilas-Boas, 1996). The results of this study indicated that arm coordination changes during the time limit test (to exhaustion) at the minimum velocity of maximal oxygen consumption (TLim-vVO2max), but not significantly for all the subjects. This is in. 35.