The effect of the number of daily training sessions on skeletal muscle protein synthesis.

The purpose of this investigation was to examine the effects of training either once or three times/day on the principal stages of skeletal muscle. The experiments were carried out on male albino rats fed either 3 or 5 times/day a diet containing 20% protein. Experimental animals swam either once or 3 times/day, 6 days/week for 10 weeks with weights attached. The total duration of daily activity was equal for both groups and at 10 weeks each animal was swimming for 60 min/day with 3% of his body weight attached. All the animals were examined at rest after the 10-week training programs. The adequacy of the weight-loading and training schedules was estimated by body weight dynamics and such energy metabolites as creatine phosphate and glycogen. Skeletal muscle RNA and protein synthesis were studied by means of 14C-orotic acid and 14C-leucine incorporation, respectively. Quadriceps and gastrocnemius muscles were used for analysis in all experiments. It was found that the increase in the number of daily training sessions resulted in an increased content and intensity of synthesis of skeletal muscle proteins as evidenced by an increase in the content of amino acids in the muscle, an increased synthesis of both microsomal and ribosomal RNA, an increased stability of (poly-A)-containing messenger RNA, and an increased synthesis of all skeletal muscle protein fractions: myofibrillar, sarcoplasmic, and myostromal.