MUSCULAR ADAPTATION AND STRENGTH DURING THE EARLY PHASE OF ECCENTRIC TRAINING - INFLUENCE OF THE TRAINING FREQUENCY

We investigated the effects of different training frequencies on maxim um isometric voluntary contraction (MVC) force and plasma concentratio ns of muscle proteins during the early phase of eccentric training. MV C and plasma concentrations oi creatine kinase (CK) and slow-twitch sk eletal (cardiac beta-type) myosin heavy chain (MHC) fragments were mea sured before and 4 and 7 d ater performing the first and last training task. Training tasks, which comprised 70 high-force eccentric contrac tions involving the thigh muscles (single leg), were performed under s upervision in three groups (A, B, C) at the beginning and at the end o f the study period (7 wk). In addition, groups A (hr = IO) and B (N = 10) trained during the study period starting I wk after the first trai ning task. Group A performed one training task once a week for 5 wk an d group B (N = 10) twice a week for 2 wk and three times a week during the subsequent 3 wk. Iii all three groups the first training task res ulted in delayed CK and MHC peaks and decrements in MVC, which were co mparable (P > 0.05). Only training regimen B resulted in a significant increase in the MVC. Compared with the first training task training r egimens, A and B significantly (P < 0.01) reduced the increase in seru m muscle protein and muscle function impairment. The responses to the last training task did not differ significantly between groups A and B . In group C the responses after the second training task did not diff er significantly from those observed after the first task. Our results suggest that, compared with group A, additional eccentric exercise in group B is the essential basis for the increase in muscle strength du ring the early phase of eccentric Raining without further benefits for muscular adaptation. in group C we found no muscular adaptation.