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. 1979 Feb;287:33–43. doi: 10.1113/jphysiol.1979.sp012643

Motor unit organization of human medial gastrocnemius.

R A Garnett, M J O'Donovan, J A Stephens, A Taylor
PMCID: PMC1281479  PMID: 430414

Abstract

1. The properties of fifty-seven motor units in human medial gastrocnemius have been studied using controlled intramuscular microstimulation, glycogen depletion and muscle biopsy. 2. Motor units could be divided into three classes on the basis of their mechanical properties. Type S units were slow, small and fatigue resistant. Type FR units were fast, intermediate in size, and fatigue resistant. Type FF units were fast, large and fatigable. 3. Glycogen depletion of a number of type S and FF units revealed them to be composed of type 1 and type 2b muscle fibres respectively. 4. The results suggest that during slowly increasing voluntary contractions where units are recruited in order of size, type 1 and 2a muscle fibres would be employed at low force levels followed by type 2b muscle fibres in stronger contractions.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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