Contractile Properties of Skeletal Muscle from Trained Miniature Pig
Format of Original
Pflügers Archiv: European Journal of Physiology
The isometric contractile properties of the tibialis anterior muscle were measured in situ in male miniature pigs. The pigs were divided into three groups at 2 months of age; one group trained by endurance running, the second group trained by sprint running and the third group served as an unexercised control. After 7 months of training, the endurance group ran continuously for 60 min at 95 m/min and a 5% slope and the sprint group ran ten 60 sec sprints at 198 m/min and a 10% slope, each sprint interspersed with a 1 min rest interval. The mean values for contraction time, one-half relaxation time, twitch tension, tetanus tension and twitch-tetanus ratio were not significantly different (P>0.05) among the three groups. Fatigability was measured by stimulating the muscle preparation for 45 min at a frequency of 4 impulses/sec. Both trained groups maintained a significantly higher (P<0.05) percentage of their maximal twitch tension than the control group over the 45 min period. These results support previous research which suggest that isometric contractile properties of whole, heterogeneous muscle resist change after chronic, physiological exercise programs. However, both types of training produced increased skeletal muscle endurance.