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 μmol/L) and high-intensity–high-frequency (0.93 ± 2.56 μmol/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 min−1 kg−1). The main effects for intensity, with respect to the change in insulin (effect size ESTIMATE = 0.46 μU/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.