The effect of the exhaustive enduring exercise training on the amount of the skeletal muscle protein and isometric tetanic force of rats

A study was conducted to examine the effects of exhaustive enduring exercise training on the skeletal muscle of rats. Twenty-six male Wistar rats were divided into 3 groups : an exhaustive training group (EE). a free-eating control group (Co), and a pair weight group in which body weight was matched to EE (PW). The rats in EE were forced to run on a treadmill with an inclination of 0 ̃ 3, 6 days/week for 4 weeks. At first the rats ran at a constant speed for 60 min. Then we gradually added 2 m/min to the basic speed every minute until they were exhausted. The tread-mill speed was 20 m/min during the first, 30 m/min during the second, 35 m/min during the third, and 40 m/min during the final week. The muscle wet weight, the quantity of the muscle protein and the isometric tetanic force were measured with the soleus and extensor digitorum longus (EDL). Food restriction induced significant decreases in EDL weight. Exhaustive enduring exercise training induced noteworthy decreases in soleus weight, but remarkable gains in EDL weight. It also induced significant changes of the quantity of the muscle protein in the two muscles, which corresponded to the changes in muscle weight. The isometric tetanic force of both muscles was not affected by food restriction. The isometric tetanic force showed a significant decreases in EDL in EE comparison Co. The isometric tetanic force of the soleus did not show a significant decreases. However, its degree of decrease corresponded to that of the muscle protein. These findings illustrate that exhaustive endur-ance exercise training induces degradation of the soleus and hypertrophy of the EDL. However, it also decrease the muscle force which generals the capacity of the two muscles. We think that this phenomenon depends on the skeletal muscle characteristics, such as fiber type, and eccentric or concentric contraction.