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Related Experiment Videos

Integrated electromyogram and oxygen uptake during positive and negative work

B Bigland-Ritchie, J J Woods

    The Journal of Physiology
    |September 1, 1976
    PubMed
    Summary

    Muscle activity and oxygen consumption are lower during eccentric (negative) work compared to concentric (positive) work, even when producing the same force. This finding highlights differences in muscle fiber recruitment and energy demands during different types of exercise.

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    Area of Science:

    • Exercise Physiology
    • Biomechanics
    • Muscle Physiology

    Background:

    • Understanding the energetic cost and neural activation patterns of different muscle contraction types is crucial for optimizing training and rehabilitation.
    • Previous research has indicated potential differences in efficiency between concentric and eccentric muscle actions, but detailed quantitative comparisons are needed.

    Purpose of the Study:

    • To quantitatively compare the integrated electromyogram (i.e.m.g.) and oxygen uptake during positive (concentric) and negative (eccentric) work at various pedaling rates.
    • To investigate the relationship between muscle activity, oxygen consumption, and mechanical torque during cycling.

    Main Methods:

    • Simultaneous measurement of integrated electromyogram (i.e.m.g.) from vastus lateralis and steady-state oxygen uptake during cycling on a motorized ergometer.

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  • Performance of standardized positive and negative work at 50 rev/min and other pedaling rates, with varying torque levels.
  • Analysis of linear relationships (r > 0.98) between i.e.m.g., oxygen consumption, and mean pedal torque, assessing reproducibility over several months.

    • Main Results:

    • Linear relationships were observed between i.e.m.g., oxygen consumption, and pedal torque, with high reproducibility.
    • The ratio of i.e.m.g. slopes for positive versus negative work was 1.96 ± 0.12.
    • The ratio of oxygen uptake slopes for positive versus negative work was significantly higher at 6.34 ± 0.82.

    Conclusions:

    • Eccentric muscle contractions require less muscle fiber activity and significantly less oxygen uptake to produce the same external force compared to concentric contractions.
    • These findings suggest a substantial energetic advantage and reduced neural demand during muscle stretching (eccentric exercise) across various cycling speeds.
    • The discrepancy in ratios highlights the complex interplay between muscle activation, mechanical output, and metabolic cost during different modes of exercise.