Effects Of A 4-month Exercise Training On Fitness, Body Composition, Blood Pressure And Autonomic Function

Abstract

Increased heart rate variability (HRV) and reduced heart rate (HR) at rest have been associated with lower mortality rate. Additionally, increases in total and central body fat are suggested to play an important role in sympathetic nervous system activation. There is evidence from cross-sectional studies that trained individuals have higher HRV, lower resting HR and less body fat than those untrained. However, on old age adults only few studies have been conducted to investigate HRV changes induced by exercise training, although not providing definitive conclusions. PURPOSE: To investigate the effects of a 4-month exercise training programs, using different exercise modes, on HRV, resting HR, aerobic fitness, blood pressure (BP), and body composition in old age individuals. METHODS: Fifty-nine older adults (68,4 ± 5,5yr) were randomized into three groups: 1) aerobic training (AT; n=20, 15-45min, 3 days/wk), 2) resistance training (RT; n=19, 15-45min, 3 days/wk) and 3) control (CG; n=20, no exercise). Groups were evaluated at baseline and after 4 months. Using a heart rate monitor, five-min recordings were carried-out after a 15-min resting period in the supine position to obtain low (LF) and high (HF) frequency indexes of HRV. Resting BP and HR were measured with an automated blood pressure monitor. The 6-minute walk test was used to evaluate aerobic fitness. Percent body fat (%BF), trunk fat and lean mass were also evaluated by Dual-energy X-ray absorptiometry. The Wilcoxon test was used to compare median pre and post-test values in each group (p<0.05). RESULTS: After 4 months, no significant differences were observed in HRV and resting HR. Conversely, aerobic fitness improved in the exercise training groups (AT - P<0.001; RT - P =0.034). SBP decreased in all groups (AT, P=0.008; ST, P=0.015; CG, P=0.048). Surprisingly, AT group, but not RT group, increased (P=0.004) lean mass. Trunk fat and %BF decreased in AT (P<0.001; P =0.001) and ST (P=0.034; P =0.012) groups but not in CG. CONCLUSIONS: Exercise training failed to improve HRV and resting HR. However, both modes of exercise training were able to ameliorate body composition and aerobic fitness in older adults. Supported by FCT (PTDC/DES/108780/2008; SFRH/BD/33124/2007).