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The Journal of Sports Medicine and Physical Fitness 2020 Oct 22

DOI: 10.23736/S0022-4707.20.10469-9

Copyright © 2020 EDIZIONI MINERVA MEDICA

language: English

Myosin heavy chain expression relationships to power-load and velocity-load curves

Michael T. LANE 1 , Andrew C. FRY 2

1 Exercise Physiology Laboratory, Eastern Kentucky University, Richmond, KY, USA; 2 Osness Human Performance Laboratories, University of Kansas, Lawrence, KS, USA


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BACKGROUND: Velocity- and power-based training are popular methods of determining training session loads and volumes. One factor that may influence load-velocity and load-power properties of an individual is the myosin heavy chain (MHC) composition of the muscle.
PURPOSE: To examine the relationship between MHC composition and both load-velocity and load-power properties of muscle performance.
METHODS: 42 Men with a variety of training backgrounds took part in this study ( ±SD; age=22.4±3.5 yrs, hgt=1.78±0.07 m, BW=78.7±13.3 kg). After testing leg extension one repetition maximum (1 RM), subjects performed maximal effort leg extensions at loads from 30% - 90% 1 RM. Muscle biopsies from the vastus lateralis were analyzed via SDS-PAGE electrophoresis technique for MHC content (IIx=13.8±12.9%, IIa=49.4±10.3%, I=36.8±11.3%). Leg extension rotational velocity and power were plotted against relative loads for all subjects.
RESULTS: Significant correlations (p<.05) were observed for MHC IIa with all performance variables (i.e., slopes, intercepts, peaks and relative loads). Relationships indicated that greater %MHC IIa was associated with greater velocity intercepts, more negative load-velocity slopes, greater maximal power, and with maximal power occurring at a lower relative intensity (% 1 RM).
CONCLUSIONS: These data indicate that muscle velocity and power characteristics appear to be partially influenced by MHC content in a manner consistent with single muscle fiber contractile properties.


KEY WORDS: Skeletal muscle; Fiber type; Leg extension; Kinetics; Kinematics

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