DIFFERENCES IN MUSCLE CONTRACTILE CHARACTERISTICS AMONG BODYBUILDERS,ENDURANCE TRAINERS AND CONTROL SUBJECTS

Citation
J. Jurimae et al., DIFFERENCES IN MUSCLE CONTRACTILE CHARACTERISTICS AMONG BODYBUILDERS,ENDURANCE TRAINERS AND CONTROL SUBJECTS, European journal of applied physiology and occupational physiology, 75(4), 1997, pp. 357-362
Citations number
35
Categorie Soggetti
Physiology
ISSN journal
03015548
Volume
75
Issue
4
Year of publication
1997
Pages
357 - 362
Database
ISI
SICI code
0301-5548(1997)75:4<357:DIMCCA>2.0.ZU;2-T
Abstract
The purpose of this investigation was to compare the myosin heavy chai n (MHC) isoform expression of the triceps brachii muscle and isoinerti al, isometric and isokinetic strength indices in competitive bodybuild ers (CB, n = 5), recreational resistance trainers (RT, n = 5): enduran ce-trained rowers (ER, n = 5) and control (C, n = 5) subjects. Muscle tissue samples were analysed for MHC isoform content using 6% sodium d odecyl sulphate-polyacrylamide gel electrophoresis. The CB possessed s ignificantly smaller (P < 0.05) percentage of MHC type IIb proteins [1 2.92 (SD 7.08)%] than RT [30.08 (SD 6.58)%] ER [31.20 (SD 2.74)%] and C [38.22 (SD 2.95)%] groups (i.e. CB < RT = ER < C). While the content of MHC type IIa isoforms did not differ significantly between the two resistance-trained groups [CB = 55.76 (SD 5.38)%; RT = 45.72 (SD 7.8) %], CB presented significantly more type IIa MHC isoforms than ER [42. 84 (SD 2.98)%] and C [34.72 (SD 1.57)%] subjects (i.e. CB = RT > ER = C). The MHC type I protein content did not differ significantly among RT [24.20 (SD 4.89)%] ER [25.38 (SD 1.67)%] and C [27.06 (SD 1.81)%] g roups. The CB [31.32 (SD 2.67)%] presented significantly more type I M HC isoforms only in comparison with RT. However, when changes in the p ercentage of MHC type I isoforms were converted to effect sizes (ES), it appeared that low statistical power rather than the absence of an e ffect accounted for the nonsignificant differences between CB and othe r groups (i.e. CB > RT = ER = C). Significant differences existed in i soinertial strength among the trained athletes (i.e. CB > RT > ER = C) , while isometric and isokinetic strength were not significantly diffe rent among any of the trained groups. However, the ES transformation o f data demonstrated that large differences existed between resistance- trained groups and ER for isometric and isokinetic: strength (i.e. CB approximate to RT > ER approximate to C). A statistically significant negative correlation (P < 0.001) was found between MHC type IIb isofor ms and isoinertial strength index (r = -0.68). The MHC type IIa protei ns were positively related to all the strength measures considered (r = 0.51 -0.61; P < 0.001). These data demonstrated different patterns o f MHC isoform expression among the different groups of athletes and it is suggested that these differences on occasion may affect the expres sion of strength.