Effects of Strength Training on Work Capacity and Parasympathetic Heart Rate Modulation During Exercise in Physically Inactive Men

Abstract

This study was designed to assess the effects of strength training on work capacity and parasympathetic heart rate modulation during exercise in physically inactive men. Seventy-four men aged 20-45 were randomly assigned to training (n=52) and control (n=22) groups. Training groups underwent 10-weeks of progressive strength training. Body composition, one-repetition maximum half-squat and maximal oxygen uptake were measured before and after the intervention. Respiratory gases, heart rate and blood lactate were recorded during a VO2max test on a cycle ergometer. Parasympathetic heart rate modulation was analyzed based on the standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) and its normalized unit (SD1n). Muscle strength and lean body mass increased in the training group. Compared to the control group, time to exhaustion increased significantly in the training group (p<0.05). SD1 and SD1n were elevated in the training group at submaximal exercise intensities (100 W, p<0.05). Blood lactate decreased at submaximal intensities when compared to the control group. Strength training increased exercise capacity, and improved vagal modulation of heart rate at submaximal exercise intensities. These changes may have favourable cardiovascular health implications for sedentary men during normal daily activities.