Effects of fatigue on activation profiles and relative torque contribution of elbow flexor synergists.
The purpose of this study was to examine changes in elbow flexion synergies as a result of fatigue. Subjects performed a series of five isometric contractions at 10% maximum voluntary contraction step intervals. Pre- and post-fatigue surface electromyograms for the muscles were rectified, integrated, normalized, a representative equation determined using the least-squares method, and the equations numerically differentiated. The differentiated curves represent the change of excitation (and therefore, change of isometric torque) with respect to the change in resultant torque (dIEMG/dT). Pre-fatigue synergy, as indicated by the dIEMG/dT, was characterized by both co-activation and trade-off patterns. The nature of the synergy was changed as a result of fatigue. This technique, focusing upon synergistic patterns, quantifies differences in excitation profiles in a manner not previously described.
Grabiner
M D
MD
Department of Physical Education and Exercise Science, University of Southern California, Los Angeles 90089-mc 0652.
Robertson
R N
RN
Campbell
K R
KR
D000328:Adult; D001696:Biomechanical Phenomena; D004550:Elbow / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*