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Oxygen availability and motor unit activity in humans

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Summary

Six men were studied to determine the interrelationships among blood supply, motor unit (MU) activity and lactate concentrations during intermittent isometric contractions of the hand grip muscles. The subjects performed repeated contractions at 20% of maximal voluntary contraction (MVC) for 2 s followed by 2-s rest for 4 min with either unhindered blood circulation or arterial occlusion given between the 1st and 2nd min. The simultaneously recorded intramuscular MU spikes and surface electromyogram (EMG) data indicated that mean MU spike amplitude, firing frequency and the parameters of surface EMG power spectra (mean power frequency and root mean square amplitude) remained constant during the experiment with unhindered circulation, providing no electrophysiological signs of muscle fatigue. Significant increases in mean MU spike amplitude and frequency were, however, evident during the contractions with arterial occlusion. Similar patterns of significant changes in the surface EMG spectra parameters and venous lactate concentration were also observed, while the integrated force-time curves remained constant. These data would suggest that the metabolic state of the active muscles may have played an important role in the regulation of MU recruitment and rate coding patterns during exercise.

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Authors and Affiliations

  1. Laboratory of Applied Physiology, College of Liberal Arts and Sciences, Kyoto University, Sakyo-ku, 606, Kyoto, Japan

    Toshio Moritani, Masashi Shibata & Tamaki Matsumoto

  2. School of Health, Physical Education and Recreation, Ohio State University, 43210, Columbus, OH, USA

    W. Michael Sherman

  3. Department of Health and Physical Education, Kyoto College of Art, 606, Kyoto, Japan

    Minoru Shinohara

Authors
  1. Toshio Moritani
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  2. W. Michael Sherman
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  3. Masashi Shibata
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  4. Tamaki Matsumoto
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  5. Minoru Shinohara
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Moritani, T., Sherman, W.M., Shibata, M. et al. Oxygen availability and motor unit activity in humans. Europ. J. Appl. Physiol. 64, 552–556 (1992). https://doi.org/10.1007/BF00843767

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  • DOI: https://doi.org/10.1007/BF00843767

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