title: Muscular adaptation and strength during the early phase of eccentric training: influence of the training frequency.
abstract: We investigated the effects of different training frequencies on maximum isometric voluntary contraction (MVC) force and plasma concentrations of muscle proteins during the early phase of eccentric training. MVC and plasma concentrations of creatine kinase (CK) and slow-twitch skeletal (cardiac beta-type) myosin heavy chain (MHC) fragments were measured before and 4 and 7 d after performing the first and last training task. Training tasks, which comprised 70 high-force eccentric contractions involving the thigh muscles (single leg), were performed under supervision in three groups (A, B, C) at the beginning and at the end of the study period (7 wk). In addition, groups A (N = 10) and B (N = 10) trained during the study period starting 1 wk after the first training task. Group A performed one training task once a week for 5 wk and group B (N = 10) twice a week for 2 wk and three times a week during the subsequent 3 wk. In all three groups the first training task resulted in delayed CK and MHC peaks and decrements in MVC, which were comparable (P > 0.05). Only training regimen B resulted in a significant increase in the MVC. Compared with the first training task training regimens, A and B significantly (P < 0.01) reduced the increase in serum 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 differ 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 during the early phase of eccentric training without further benefits for muscular adaptation. In group C we found no muscular adaptation.
authors.affiliation: Department of Medical Chemistry and Biochemistry, University of Innsbruck Medical School, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Sorichter
authors.forename: J
authors.initials: J
authors.lastname: Mair
authors.forename: A
authors.initials: A
authors.lastname: Koller
authors.forename: P
authors.initials: P
authors.lastname: Secnik
authors.forename: V
authors.initials: V
authors.lastname: Parrak
authors.forename: C
authors.initials: C
authors.lastname: Haid
authors.forename: E
authors.initials: E
authors.lastname: Müller
authors.forename: B
authors.initials: B
authors.lastname: Puschendorf
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D003402:Creatine Kinase / Q000097:blood; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction; D007866:Leg / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins / Q000097:blood; D018482:Muscle, Skeletal / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000097:blood; D013997:Time Factors; D019210:Troponin I / Q000097:blood
chemical_list: D009124:Muscle Proteins; D019210:Troponin I; D003402:Creatine Kinase; D018995:Myosin Heavy Chains