O estudo piloto foi realizado junto a uma amostra de 30 pacientes. Destes, 10 pacientes foram descontinuados do estudo ainda na etapa I por motivos: suspensão médica para o treinamento físico (50%), desistência do treinamento físico por motivos financeiros (30%) e faltas consecutivas às sessões de treinamento físico (20%). Os resultados do estudo piloto foram utilizados para a realização do cálculo amostral.
Dentre os 20 pacientes que permaneceram no estudo piloto, 65% são do sexo feminino, média de idade de 55,0±10,9 anos, 4,5±4,0 anos de escolaridade, inativos profissionalmente (65,%) e com renda mensal individual 1,1±1,1 salários mínimos e familiar de 3,3±1,2 salários mínimos.
A hipótese de diagnóstico médico mais frequentre nesta amostra foi também a HAS (100,0%) Em relação aos dados do ecocardiograma, observou-se fração de ejeção média de 65,9±5,3%. A Tabela 2 apresenta a distribuição das variáveis e a relação entre os sintomas cardiovasculares e as medicações em uso da população estudada no estudo piloto.
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Tabela 2: Caracterização da amostra do Estudo Piloto (n=20). Campinas, 2011.
Variável Média (dp)* Mediana IQR** Distribuição em
Categorias
N %
Idade 55(10,9) 58,5 20,7
Escolaridade (anos) 4,5(4,0) 4,0 7,0
Renda Mensal familiar§ 3,3(1,2) 2,5 3,3
Sintoma Cardiovascular palpitação edema fadiga dispnéia lipotímia precordialgia 9 8 7 7 5 5 45 40 35 35 25 25
Hipótese Diagnóstica HAS
Coronariopatia RM*** 20 2 2 100 10 10 Medicação Antitrombótico Diurético Estatina Bloqueador canal Ca IECA**** β bloqueador Ant. Recept. Angio
12 10 10 8 7 7 6 60 50 50 40 35 35 30
* dp= desvio padrão **IQR= Interquartile range (Quartil 75- Quartil 25) ***RM = Revascularização do Miocárdio **** IECA = inibidor enzima conversora de angiotensina; § Salário Mínimo= R$ 510,00
Em relação aos pacientes descontinuados do estudo piloto, 50% da amostra pertenciam ao grupo intervenção e 50% ao grupo controle, 50% da amostra são do sexo masculino, com média de idade de 51±8,6 anos, 9±3,2 anos de escolaridade, renda mensal individual de 1,6±1,7 salários mínimos e familiar de 3,5±2,4 salários mínimos e inativos profissionalmente (70,0%) A principal hipótese de diagnóstico médico foi a HAS (90,0%).
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Tabela 3: Distribuição das variáveis dos pacientes descontinuados do Estudo Piloto (n=10).
Campinas, 2011
Variável Média (dp)* Mediana IQR** Distribuição em
Categorias
N %
Idade 51(8,6) 51,0 12,2
Escolaridade (anos) 9(3,2) 8,0 2,2
Renda Mensal familiar§ 3,5(2,4) 2,7 3,2
Sintoma Cardiovascular Precordialgia Palpitação fadiga edema dispnéia lipotimia 4 3 3 2 2 1 40 30 30 20 20 10
Hipótese Diagnóstica HAS
Coronariopatia RM*** 9 2 1 90 20 10 Medicação Diurético Antitrombótico Bloqueador canal Ca Estatina IECA**** β bloqueador Ant. Recept. Angio
8 6 5 4 4 3 1 80 60 50 40 40 30 10
* dp= desvio padrão **IQR= Interquartile range (Quartil 75- Quartil 25) ***RM = Revascularização do Miocárdio **** IECA = inibidor enzima conversora de angiotensina; § Salário Mínimo= R$ 510,00
No estudo piloto, a intensidade do treinamento dada pela velocidade crítica do PDE foi reajustada sempre que pacientes detectavam uma percepção de esforço inferior a pontuação 13 pela escala de Borg. Foi observado que esse reajuste correspondeu a uma média de 5% de aumento da velocidade crítica. A escala de Borg foi essencial para o ajuste do treinamento.
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Os resultados deste estudo estão apresentados sob a forma de artigos submetidos à publicação em periódicos internacionais.
19. Artigo referente Etapa 1. BENEFITS OF USING A NON-EXHAUSTIVE PROTOCOL TO DETERMINE THE INTENSITY OF AEROBIC TRAINING IN THE CONTEXT OF CARDIOVASCULAR DISEASE
20. Artigo referente Etapa 2. EFFECTIVENESS OF EDUCATIONAL INTERVENTION PROGRAM FOR MAINTAINING THE PHYSICAL ACTIVITY BEHAVIOUR AFTER CARDIAC REHABILITATION
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BENEFITS OF USING A NON-EXHAUSTIVE PROTOCOL TO DETERMINE THE INTENSITY OF AEROBIC TRAINING IN THE CONTEXT OF CARDIOVASCULAR DISEASE
Abstract
The aim of this study was to evaluate the benefits of a program of aerobic exercise training based on non-exhaustivedouble efforts protocol as a method to prescribe the exercise intensity among cardiovascular disease patients. This quasi-experimental study used a pre-post- intervention design with a 12-week follow-up and enrolled 67 patients. The intensity of the aerobic exercise training was based on the results of four aerobic exercise tests carried out at random orderat different intensities on a motorized treadmill. The non-exhaustive double efforts protocol was based on estimations of oxygen consumption and heart rate deltas obtained at each test to determine the critical speed. The aerobic exercise training consisted of walking on a treadmill/ 3x week /12 weeks. The target outcomes were: physical capacity (oxygen uptake at effort testing, critical speed from non-exhaustive double efforts protocol; and the Veterans Specific Activity Questionnaire) and cardiometabolic risk factors (waist circumference, body composition and lipid profile). Results: At the end of the follow-up, there was an increase of 14.4% in oxygen uptake (p< 0.0001) and an increase in the critical speed of 12.3% (p<0.0001). Additionally, a reduction in waist circumference of 2.8% (p<0.0001) and an increase of 6.2% in HDL-cholesterol (p=0.0159) were observed. Conclusion: The physical training based on the intensity estimated by the non-exhaustive double efforts protocol resulted in significant improvements in physical capacity as well as in some cardiovascular risk markers. Thus, the protocol seems to be an interesting method for intensity prescription of the physical training of cardiovascular disease patients.
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Key words: exercise; exercise test; exercise tolerance; physical fitness; intervention studies;
cardiovascular disease.
Introduction
The reduction of mortality related to cardiovascular diseases can at least in part be attributed to an increase in exercise capacity which may be the result of regular aerobic exercise [18,19]. Furthermore, physical activity has demonstrated impact on cardiometabolic risk factors, as well as the indicator of visceral obesity and lipid profile [28,32].
As a result, clinical guidelines stress the importance of exercise training as part of cardiac rehabilitation programs (CRP) [1,13,16,29]. However, there is a paucity of alternative protocols
to determine the training intensity, when the gold standard protocol to determine physical capacity, the cardiopulmonary exercise testing (CPX), is not available especially by financial constraints [5].
Protocols using submaximal parameters have been described as potential interesting alternative methods for physical activity prescription in the context of cardiovascular disease (CVD) [25]. The rational of these protocols is based on the identification of the transition zone
from the aerobic to anaerobic metabolism as the zone for exercise prescription. This interval marks the upper limit of an almost exclusively aerobic metabolism toward a predominance of anaerobic metabolism, but in which a steady state is still possible. Thus, it indicates the intensity of an activity in which the maximal steady state or work rate can be maintained through all the performance of a longstanding submaximal exercise [2] for a given individual [21,24]. For this reason, the intensity of activity encompassed in this transition zone can be considered appropriate to improve cardiorespiratory fitness [18,31].
Different protocols permit the identification of the metabolic transition zone in humans [9,18,27,35]. Among those, there is the non-exhaustive double efforts (NEDE) protocol
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developed in the ‗80s by Chassain (1986) aimed at determining aerobic capacity. This method is based on physiological responses of heart rate (HR), oxygen uptake (VO2) and blood lactate to
exercise. This procedure assumes that the aerobic-anaerobic transition is delimited by the highest exercise intensity at which the physiological variables are in a steady state and which aerobic metabolism still prevails over the anaerobic metabolism, during a constant-load exercise. The protocol consists of four intermittent double bouts of non-exhaustive exercise at different intensities, with 3-min of effort intercalated by 1.5 min of rest. At the end of each double effort, the deltas of the aforementioned physiological variables are determined, resulting in four deltas to each variable. The maximal steady state is determined from a linear interpolation (speed versus deltas) and the y-intercept of linear interpolation is the "null delta variable" equivalent to the critical velocity (CV) which theoretically represents the maximal steady state of these variables. The NEDE does not result in body exhaustion, which may be considered as a great advantage for individuals presenting limitations to perform physical efforts as CVD patients. The applicability and potential advantages based in this protocol has been described in humans and animal models [6,7,17,22,23]. But, to the best of our knowledge, no study evaluated the benefits of NEDE among CVD patients, in the clinical context of CRP. The greatest advantage of NEDE application among this population is the non-exhaustive characteristics of the protocol and the possibility to determine, individually, the physical training intensity for obtaining aerobic and cardiovascular improvements. Furthermore, it is possible to determine this intensity without a maximal effort application, broadening the use of the protocol in the clinical context. Thus, the aim of this study was to evaluate the benefits of an aerobic exercise training (AET) program based on NEDE protocol as a method to prescribe the exercise intensity for CVD patients. The benefits of the protocol were evaluated by the changes observed in aerobic capacity and clinical variables related to cardiovascular risk.
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METHODS
This is a quasi-experimental study with a pre-post-intervention design. Measures were obtained after the initial assessment at baseline (T0), and at the end of the program (T3), after
12-week aerobic exercise training (AET). The study was conducted at a service of cardiovascular rehabilitation of a public ambulatory of medical specialties in Southeast Brazil.
Participants
The population consisted of patients both sexes, classified as low risk for physical training (classes A and B) according to the criteria of the American Heart Association [13] with coronary artery disease (CAD) or hypertension stage I and II referred by the cardiologist after risk stratification and medical release to TEC routine and consequently to the CRP. Patients
presenting obesity grade III (Body Mass Index (BMI)>40kgm2); complex not controlled ventricular arrhythmias, insulin-dependent diabetes mellitus, valve disease or no physical condition to exercise were excluded.
The study was conducted in accordance with resolution 196/96 of the National Health Council and approved by the local Ethical Committee (Document No. 286/2011). All participants gave written informed consent.
INTERVENTION
Determination of training intensity by the Non-Exhaustive Double Efforts protocol (NEDE).
In this study, NEDE protocol was used as a prescriptive method to determine the training intensity. This protocol was adapted for CVD patients. The peak metabolic equivalents (peak
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METs) were derived from CPX. For determination of the intensity of the AET, patients performed four aerobic exercise double efforts on a motorized treadmill (Inbrasport/ Super ATL/Porto Alegre/RS/Brazil) at different intensities. The 4 tests were accomplished in two days, using submaximal efforts intensities equivalent to 70%, 65%, 60%, and 55% of the peak activities [3] (Figure 1). For each test, non-exhaustive double-intermittent efforts bouts of 180 seconds were METs derived from CPX which were further converted into speed (km/h) based on the Compendium of physical performed at the same intensity intercalated by a 90 seconds of rest. The intensities were carried out at random order. Measures of oxygen consumption (VO2) and
HR were obtained at the end of each effort. HR and VO2 delta measures were calculated by
subtracting the values of these variables obtained at the end of the second 3-min effort (E2) from the values of the first 3-min effort (E1) for each intensity, (ΔHR= HRE2 – HRE1, and ΔVO2= VO2 E2
- VO2 E1) (Figure 2). Then, a linear interpolation done, based on the deltas of HR and VO2 with
their respective speeds. The y-intercept of linear interpolation was the "null delta" equivalent to the critical speed in which the variables HR and VO2 are theoretically at a maximal steady state
[9]. Afterwards, two different linear equations were obtained for each variable and the presenting greater linearity (R2 closer to 1) was used to identify the critical speed (Figure 3), which was further used to prescribe the intensity of AET in km/h. The critical speed identified from the delta zero corresponds theoretically to the highest exercise intensity in which the aerobic metabolism predominates, representing also the point of transition between the aerobic and anaerobic metabolisms (Figure 3).
Aerobic training (AET).
The AET consisted of 35 min treadmill (Johnson Health Tech Co./GS 500/Taichung/Taiwan) walking sessions, three times a week, during 12 weeks. Each exercise session was broken down into 10 min of warm-up with stretching to upper and lower limbs, 35
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min of aerobic training in the speed determined by the NEDE and 10 min of cool-down. The maximum absences allowed were 3 sessions. Blood pressure, HR, pulse, and ratings of perceived exertion by the Borg scale were assessed at the beginning and at the ending of each session. Criteria used to interrupt the training were: cardiovascular symptoms, decrease in systolic BP levels above 15 mmHg or ventricular arrhythmia. The appropriateness of the exercise intensity was re-evaluated after 4 weeks of training. Another NEDE was performed for all participants and the training intensity was adjusted for those presenting scores of 12 and less on the Borg Scale (perception of an easy task).
OUTCOME MEASURES
Physical capacity.
Physical capacity was measured by the cardiopulmonary exercise testing, using the direct measure of uptake VO2, the gold-standard for its evaluation, the VO2 estimated from ergometer used in the effort testing and the subjective measure questionnaire (VSAQ), indicating the perception of physical capacity.
Cardiopulmonary Exercise Testing.
Symptom limited maximal exercise testing with VO2 analysis was performed on a
treadmill (Inbrasport/Super ATL/Porto Alegre/RS/Brazil) using Ramp protocol. The ramp protocol was personalized to achieve a peak exercise of between 8-12 minutes. The exercise was terminated for generalized fatigue, symptom or sign limits, or electrocardiographic changes. The patient was connected to a metabolic gas analyzer (VO2000, Aerosport, Medgraphics, St Paul, Minnesota) through which the gas samples were collected and measured each 10 seconds during the test. Peak VO2 was defined as the maximum oxygen consumption attained at the end
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of exercise testing. ―Measured METs‖ were determined by directly measured VO2 (milliliters per
kilogram body weight per minute) divided by 3.5. ―Estimated METs‖ were determined from treadmill speed and grade at peak exercise according to the American College of Sports Medicine recommendations [4].
The CPX was not only used to estimate the physical capacity as an outcome for the traininig protocol, but also to determine the intensities of the NEDE protocol. The CPX was used as parameter in this study, considering its value as gold standard in the determination of physical capacity.
Veterans Specific Activity Questionnaire (VSAQ).
The VSAQ-Brazilian version [11] consists of a list of activities presented in progressive order according to METs, allowing determination of different intensities of daily activities limited by cardiovascular disease symptoms or physical exhaustion. The scale ranges from 1 to 13 METs. The VSAQ score is age-adjusted by using a nomogram according to the equation: METs = 4.7 + 0.97 (VSAQ) - 0.06 (age) [36].
Metabolic Evaluation
Waist circumference.
Waist circumference was determined as the greater of two measurements calculated to the nearest 0.1 cm midway between the lower rib margin and the iliac crest after a normal expiration [12].
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Body composition.Body composition was measured with a bioimpedance scale (InBodyR20/Biospace Co./South Korea) with patients in orthostatic position. The patient was instructed to not eat and not drink liquids 8 hours before, have urinated and evacuated, don´t do exercises before testing and women shouldn´t be menstruating. The balance presented information regarding weight (kg), fat mass (kg), body mass index (BMI) calculated as a ratio of weight to height (kg/m2) and the percentage of body fat (%).
Lipid profile.
Lipid profile was measured from fasting blood samples that were drawn after an overnight 12-hour fast. Total cholesterol (TC), High-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) were measured. The Low-density lipoprotein - cholesterol (LDL-C) was determined by the Friedewald equation for TG <300 mg / dl [30].
STATISTICAL ANALYSES
Initially, data were screened for normality, homogeneity of variance within each group and outliers. Afterwards, the paired t-test and the Wilcoxon Signed-Rank test were used respectively for variables exhibiting normal and non-normal distribution to compare repeated measures, assessing difference in score from pre to post test. The software SAS for Windows, version 9.2 (Statistical Analysis System Institute Inc., Cary, NA, 2002-2003) was used for all analyses. The significance level of p-value <0.05 was adopted.
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RESULTS
From the 118 patients initially screened to participate in the study, 90 were actually recruited. Reasons for exclusion were: suspension of the medical authorization to participate in the PCR (n=17); refusal to take part in the study (n=10), and death (n=1). From the 90 enrolled patients, 67 patients completed the follow-up, with a attrition of 25%. Twenty-three patients were discontinued for the following reasons: abandonment (n=14) and suspension of medical authorization to continue the PCR (n=09).
Participants who completed the program were in average 55.7 ± 10.2 years old, female (68.6%) with a medical diagnosis of hypertension (54 or 80.6%), CAD (5or 7.5%), or hypertension + CAD (8 or 11.9%). Regarding the associated risk factors or comorbidities, 37.3% participants presented dyslipidemia; 8.9% were smokers; and 89.5% were in overweight or obese with a mean body mass index of 30.3 ± 53.8kg/m2 (Table 1).
AET guided by the NEDE promoted a significant increase of the APC and this according to the direct measure of VO2 max (mL.kg-1.min-1)(20.5 ± 4.8 x 24.0 ± 6.6, p<0,0001) as well as
the METs estimated by ergometer used in the effort testing (8.0 ± 2.4 x 10.1 ± 2.5, p<0,0001). It represents an improvement in average of 14.4% in the VO2 max, and of 20.8% in the METs
estimated by CPX. In fact, 57% of patients showed an increase ≥10% in VO2 max and 79% of
patients showed an increase ≥10% in the METs estimated by ergometer. Regarding the NEDE Protocol, there was a significant increase in critical speed reached at the end of the AET (5.0 ± 0.9 x 5.7 ± 1.1, p<0.001) (Table 2).
Although an augmentation has been noted also for the perceived APC measured by the VSAQ, this difference was not statistically significant (Table 2).
There was a general improvement of the variables related to the metabolic profile. Significant reduction were observed for the waist circumference (cm) (103.9 ± 11.8 x 101.3 ±
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11.6, p<0,0001) with a reduction of 2.8%. The HDL-C (mg/dL) levels (45.3 ± 9.8 x 48.1 ± 12.7, p=0,0159) exhibited an significant increase of 6.2%. Decreasing, but not statistically significant differences were observed for the other metabolic evaluations: COL-T (mg/dL), LDL-C (mg/dL), TRIGL (mg/dL), BMI (kg/m2) and percentage body fat.
DISCUSSION
This study was aimed at evaluating the benefits of a APT based on NEDE protocol for the determination of individualized prescription of aerobic exercise intensity for CRP patients.
The protocol was adapted for a moderate training intensity between 55-70% of the VO2 max as
recommended by ACSM for non-conditioned individuals [14].
In the last 30 years, there was a significant progression in the studies involving the comprehension of the effects of exercise in the transition zone from aerobic and anaerobic metabolism [9,27,35]. Regarding the NEDE, previous studies had already used protocols based in this method comparing the correlations between the critical speed with the maximal lactate steady state (MLSS) in humans and in rats, indicating that this method offers a potential determination of aerobic capacity [6,22,23]. But how effective could be the protocol in improving exercise capacity and changing cardiovascular risk markers among CRP patients remained a
question to be investigated.
In this study, we used the CPX in a direct incremental test, to prescribe the 70% predictive loads of the METs max and then, determine the intensities of the NEDE protocol. It is unquestionable that the direct spirometry, as a gold standard at determining the physical capacity, would be sufficient to individualize the prescription of exercise intensity with higher accuracy than the NEDE protocol. But the purpose of its use in this study was to count on a gold standard to evaluate the benefits of the NEDE protocol, which has been never used before to
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prescribe the training intensity in cardiac rehabilitation. In the future, it is possible to consider the use of other measure to identify the intensity corresponding to 70 % of the METs max from VSAQ, a self-reported measure of physical capacity.
In the final evaluation, after aerobic training, we could demonstrate by the direct spirometry an increase of peak VO2 in average by 3.46 mL/kg/min, equivalent to 0.99 METs.
Considering the indirect values, estimated from ergometer used in the effort testing, the increase of VO2 was in average 7.4 mL/kg/min, equivalent to 2.1 METs after 12 weeks after the beginning
of the AET. Both measures point to a substantial improvement of the physical capacity.
It´s well known that aerobic exercise programs increase maximal oxygen uptake (VO2
max). Systematic review and meta-analysis concerning coronary heart diseases patients showed that exercise training interventions improve VO2 max in average by 2.3 mL/kg/min (0.66
MET; net change between the training and control groups). It is also observed that the effect is larger when the interventions imply aerobic training [34].
Additionally, meta-analysis indicate that 1MET increases in aerobic capacity are associated with 13% and 15% decreases in the risk of all-cause and CHD mortality in healthy men and women, respectively [19]. This is well in line with large observational studies that have indicated that 1MET increase in aerobic capacity translates to a 12–13% improvement in