Non-Uniform Changes in Muscle Fiber Conduction Velocity during Sustained Isometric Contraction of the Vastus Medialis Muscle

Document Type : Original Article

Abstract

Muscle fiber conduction velocity (MFCV) decreases during sustained fatiguing contraction due to metabolic 
accumulation. Differences in morphological and architectural characteristics of muscle fibers within the vastus 
medialis muscle may result in non-uniform metabolites accumulation and as consequence non-uniform 
changes in fiber conduction velocity. The aim of this study was to assess muscle fiber conduction velocity at 
the level of single motor unit in different locations of the vastus medialis muscle during sustained contraction. 
Surface and intramuscular EMG signals were recorded from two locations of the right vastus medialis muscle 
of ten healthy men during 70s isometric contraction at 20% of the maximal force. The distal location of the 
vastus medialis muscle resulted in a larger value of conduction velocity (p < 0.05) and greater conduction 
velocity rate of reduction (p < 0.05) during sustained contraction compared with the proximal region. These 
results indicated a non-uniform change in electrophysiological membrane properties at different locations of 
the vastus medialis muscle during sustained contraction.

Keywords

• conduction velocity
• fatigue
• muscle locations

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