Heart rate variability and intensity of habitual physical activity in middle-aged persons

Purpose: In the middle-aged, it has been shown that moderate physical activity is associated with increased global HR variability (HRV) and vagal-related HRV indexes. However, the relative effect of quantity and intensity of physical activity on HRV is still unknown. The purpose of this study was to compare HRV indexes in three groups of subjects presenting different long-term physical activity profiles: sedentary subjects (SED) with low-energy expenditure (PAEE) and two groups of subjects with equivalent moderate PAEE, but differing in terms of intensity of physical activity (active (ACT) and sportive (SP) individuals). Methods: Forty-three middle-aged subjects (61.2 +/- 4.3 yr) were divided into the three groups on the basis of a physical activity questionnaire (Modified Baecke Questionnaire for Older Adults). Physical activity was evaluated by accelerometry for 1 wk. Time and frequency domain HRV indexes were determined during quiet periods in the morning on 5-min stationary R-R interval segments under controlled breathing. Quality of life was evaluated using the SF-36 Health Survey Questionnaire. Results: SP spent more time in moderate to very high activities than ACT (2.1 +/- 0.1 vs 0.6 +/- 0.1 h(.)wk(-1); P < 0.05) and less time in very light to light activities (62.8 +/- 2.0 vs 73.7 +/- 1.7 h(.)wk(-1); P < 0.05). SP presented higher vagal-related HRV indexes than SED (P < 0.05), whereas increases in ACT were less marked. ACT and SP had similar health status scores, which were higher than for SED (P < 0.05). Conclusions: In older adults with different lifestyles, habitual moderate PAEE is associated with better self-estimated overall health status and higher vagal-related HRV indexes compared with subjects with low PAEE, especially when moderate- to very high-intensity physical activities are undertaken.