Effect of extra-weight loading and aerobic running training on contractile properties of gastrocnemius muscle in hamsters

ABSTRACT

The effect of extra-weight loading was studied using Syrian [CHF 148] hamsters. Thirty animals were divided into three groups sedentary control [SC], sedentary extra-weight loaded [SEW] and extra-weight loaded and aerobic running training [EWAT]. The animals were made to carry extra weight [15% of body weight] continuously for 8 weeks. Additionally, aerobic running training was provided to the EWAT group with gradually increased loading. Contractile characteristics of gastrocnemius muscles were determined in vitro. Means of body mass and gastrocnemius mass were compared. Body mass and gastrocnemius mass increased significantly in the SEW group. Twitch tension was enhanced in both the SEW and EWAT groups. Tetanic tension was significantly higher only in the EWAT group. Compared to the SC group, time to peak and half relaxation time significantly increased in gastrocnemius muscles of SEW hamsters and decreased in EWAT hamsters. The tension values for development during tetanic contraction and decline during relaxation were considerably higher for the EWAT group. Similar values were obtained for the SC and SEW groups. The findings indicate that, whereas constant extra-weight loading may increase muscle mass, it decreases muscle contraction speed and does not affect muscle tension. In contrast, constant extra-weight loading combined with aerobic running training enhances the contractile characteristics of muscles