Effects of exercise on emerging and traditional cardiovascular risk factors

Background. Common cardiovascular disease risk factors (e.g., insulin and aerobic fitness) are improved with exercise; however, few studies have addressed the potential for training to modify emerging cardiovascular disease risk factors such as homocysteine and high-sensitivity C-reactive protein. Methods. Sedentary adults (n = 324, 48.9 +/- 8.4 years) were randomized to four groups differing in training intensity (moderate = 45-55% or high = 65-75% of heart rate reserve) and frequency (low = 3-4, 30-min sessions/week or high = 5-7, 30 min-sessions/week). Results. Within-group changes in homocysteine, insulin, and aerobic fitness were significant (all P < 0.0125). Furthermore, homocysteine increased in the high-intensity-low-frequency (0.98 +/- 2.32 mumol/L) and high-intensity-high-frequency (0.93 +/- 2.56 mumol/L) groups, while aerobic fitness increased in the moderate-intensity-high-frequency (0.99 +/- 2.01 mL min(-1) kg(-1)) and high-intensity-high-frequency (1.77 +/- 2.97 mL min(-1) kg(-1)) groups (all P < 0.003). The change in aerobic fitness was greater in the high-intensity-high-frequency compared to the moderate-intensity-low-frequency group (1.77 +/- 2.97 vs. 0.36 +/- 2.10 mL min(-1) kg(-1), P = 0.0014) (effect size estimate = 0.60 mL mm(-1) kg(-1)). The main effects for intensity, with respect to the change in insulin (effect size estimate = 0.46 muU/mL), and frequency, with respect to the change in aerobic fitness (effect size estimate = 0.38 mL min(-1) kg(-1)), were significant (P < 0.0125). Conclusion. Although frequent bouts of higher intensity exercise were particularly effective in reducing fasting insulin and improving fitness, they resulted in slightly increased homocysteine levels. (C) 2004 The Institute For Cancer Prevention and Elsevier Inc. All rights reserved.