Dose-response relationship between very vigorous physical activity and cardiovascular health assessed by heart rate variability in adults: Cross-sectional results from the EPIMOV study.

The minimum amount of physical activity needed to obtain health benefits has been widely determined. Unlikely, the impact of extreme amounts of very vigorous physical activity (VVPA, ≥ 8 metabolic equivalents) to the heart remains controversial. We aimed to evaluate the dose-response relationship between VVPA and heart rate variability (HRV) in adults. We selected 1040 asymptomatic individuals (60% women, 42 ± 15 years, 28 ± 6 kg/m2) from the Epidemiology and Human Movement Study (EPIMOV). Participants remained in the supine position for 10 min, and we selected an intermediate 5-min window for HRV analysis. The standard deviation of the RR intervals, root mean square of RR intervals, successive RR intervals that differ > 50 ms, powers of the low-and high-frequency bands and Poincaré plot standard deviations were quantified. Participants used a triaxial accelerometer (Actigraph GT3x+) above the dominant hip for 4-7 consecutive days for quantifying their physical activity. We also evaluated the maximum oxygen uptake ([Formula: see text]) during an exercise test. We stratified participants into five groups according to the VVPA in min/week (group 1, ≤ 1.50; 2, 1.51-3.16; 3, 3.17-3.54; 4, 3.55-20.75; and 5, > 20.75). The linear trends of the HRV through the quintiles of VVPA were investigated. We used logarithmic transformations to compare the five groups adjusted for age, sex, cardiovascular risk, and [Formula: see text]. We found a better HRV with increased VVPA for all HRV indices studied (p trend < 0.05). However, group 5 did not differ from group 4 (p > 0.05) for none of the indices. We conclude that there is an incremental benefit of VVPA on HRV of asymptomatic adults. Since we found neither additional benefits nor the harmful impact of amounts of VVPA as high as 22 min/week on HRV, our results should not discourage asymptomatic adults to perform VVPA.

Screening for physical inactivity among adults: the value of distance walked in the six-minute walk test. A cross-sectional diagnostic study.

CONTEXT AND OBJECTIVES: Accelerometry provides objective measurement of physical activity levels, but is unfeasible in clinical practice. Thus, we aimed to identify physical fitness tests capable of predicting physical inactivity among adults. DESIGN AND SETTING: Diagnostic test study developed at a university laboratory and a diagnostic clinic. METHODS: 188 asymptomatic subjects underwent assessment of physical activity levels through accelerometry, ergospirometry on treadmill, body composition from bioelectrical impedance, isokinetic muscle function, postural balance on a force platform and six-minute walk test. We conducted descriptive analysis and multiple logistic regression including age, sex, oxygen uptake, body fat, center of pressure, quadriceps peak torque, distance covered in six-minute walk test and steps/day in the model, as predictors of physical inactivity. We also determined sensitivity (S), specificity (Sp) and area under the curve of the main predictors by means of receiver operating characteristic curves. RESULTS: The prevalence of physical inactivity was 14%. The mean number of steps/day (≤ 5357) was the best predictor of physical inactivity (S = 99%; Sp = 82%). The best physical fitness test was a distance in the six-minute walk test and ≤ 96% of predicted values (S = 70%; Sp = 80%). Body fat > 25% was also significant (S = 83%; Sp = 51%). After logistic regression, steps/day and distance in the six-minute walk test remained predictors of physical inactivity. CONCLUSION: The six-minute walk test should be included in epidemiological studies as a simple and cheap tool for screening for physical inactivity.