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Muscle‐fiber conduction velocity during concentric and eccentric actions on a flywheel exercise device
Author(s) -
Pozzo Marco,
Alkner Björn,
Norrbrand Lena,
Farina Dario,
Tesch Per A.
Publication year - 2006
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.20574
Subject(s) - isometric exercise , concentric , eccentric , electromyography , flywheel , muscle fatigue , physical medicine and rehabilitation , nerve conduction velocity , muscle fibre , vastus medialis , vastus lateralis muscle , mathematics , biomedical engineering , medicine , anatomy , physical therapy , physics , skeletal muscle , geometry , engineering , quantum mechanics , aerospace engineering
A gravity‐independent flywheel exercise device (FWED) has been proven effective as a countermeasure to loss of strength and muscle atrophy induced by simulated microgravity. This study assessed muscle‐fiber conduction velocity (CV) and surface EMG instantaneous mean power spectral frequency (iMNF) during brief bouts of fatiguing concentric (CON) and eccentric (ECC) exercise on a FWED in order to identify electromyographic (EMG) variables that can be used to provide objective indications of muscle status when exercising with a FWED. Multichannel surface EMG signals were recorded from vastus lateralis and medialis muscles of nine men during: (1) isometric, 60‐s action at 50% of maximum voluntary action (MVC); (2) two isometric, linearly increasing force ramps (0–100% MVC); and (3) dynamic CON/ECC coupled actions on the FWED. Muscle‐fiber CV and iMNF were computed over time during the three tasks. During ramps, CV, but not iMNF, increased with force ( P < 0.001). Conduction velocity and iMNF decreased with the same normalized rate of change in constant‐force actions. During CON/ECC actions, the normalized rate of change over time was larger for CV than iMNF ( P < 0.05). These results suggest that, during fatiguing, dynamic, variable‐force tasks, changes in CV cannot be indirectly inferred by EMG spectral analysis. This underlines the importance of measuring both CV and spectral variables for muscle assessment in dynamic tasks. Muscle Nerve, 2006