Original articleNonuniform Activity of Human Calf Muscles During an Exercise Task
Section snippets
Overview
All subjects had pre- and postexercise T2 sequences and pre-exercise T1 sequences of the right or both legs while secured in a volumetric coil. The T1-weighted images were used to help define the anatomy within axial sections. Subjects performed heel raises after the pre-exercise scans. T2-weighted sequences were performed immediately after each exercise bout, and there was a rest period of at least 40 minutes between exercise bouts. Forty minutes of rest was chosen because T2 time recovers
Results
Two subjects were not used for analysis because their pre-exercise images had extensive noise that made these sections unreliable to use as the baseline measurement to determine percentage change with exercise.
Discussion
There are many muscles that can contribute to the plantarflexion force necessary for heel raises, including those muscles analyzed in our study. All of these muscles had changes in T2 time, but the changes were not equal among muscles and there was some intersubject variability. In particular, the medial gastrocnemius was more active than the lateral gastrocnemius. In addition, the peroneus longus, which is typically thought of as primarily an evertor or abductor of the foot, is active. Most
Conclusions
Because multiple muscles usually contribute to a movement, knowledge of the global functioning (organization of whole limb or segment) of the neuromuscular system is critical for understanding normal movement and developing new treatments and evaluative tools for patients. Thus, we must be able to simultaneously determine the activity of many spatially dispersed groupings of active muscle units. Traditional electromyographic recording techniques have been used to try to determine global
Acknowledgments
We thank Marsha Ward and Janet Kindschuh for technical assistance, Sara Giordano for comments on the manuscript, and George Cotsonis for help with statistical analyses and interpretation.
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Supported by the National Institute of Child Health and Human Development (grant no. HD 32571).
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