Abstract:
The exercise dose required to elicit positive modifications of cardiovascular disease (CVD) risk factors in individuals at risk for CVD remains unclear. PURPOSE: To determine the effect of exercise training volume on cardiorespiratory fitness as indicated by maximal oxygen uptake (VO2max), insulin resistance, traditional (LDL, HDL, and total cholesterol, glucose, blood pressure and body mass) and non-traditional (C-reactive protein) CVD risk factors in sedentary, overweight/obese individuals at moderate risk of CVD. METHODS: Fifty-seven individuals were randomised into one of four groups: 1) non-exercise control (n=13); 2) LVMI (n=15; low-volume, moderate-intensity exercise (8 kcal/kg/week)); 3) HVMI (n=15; high-volume, moderate-intensity exercise (16 kcal/kg/week)); or 4) HVHI (n=14; high-volume, high-intensity exercise (16 kcal/kg/week)) for 12 weeks. Only controls, LVMI and HVMI were examined in this thesis. Linear regression models, which controlled for age and gender, were used to determine the effect of exercise training volume on the mean change in outcomes over 12 weeks. RESULTS: HVMI demonstrated a significantly greater increase in VO2max compared to controls (P=0.04) and LVMI (P=0.03). Changes in insulin resistance did not reach statistical significance among groups (P=0.1). Exercise groups had a significant reduction in systolic blood pressure (≈11 mmHg) compared to controls (P≤0.02), but were not significantly different from each other (P=0.81). HDL cholesterol increased more in HVMI than LVMI (P=0.04); however, there were no significant differences among groups in body mass, waist circumference and other serum lipid parameters. CONCLUSION: Previously sedentary, middle-aged, overweight and obese individuals demonstrate a greater increase in VO2max with high volume compared to low volume exercise training. Findings from the current study may allow for more appropriate tailoring of exercise volume recommendations to help reduce the burden associated with CVD.
