Ankle flexor muscles in the cat: Length‐active tension and muscle unit properties as related to locomotion

G. E. Goslow, W. E. Cameron, D. G. Stuart

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

The mechanical properties of the whole muscle and fast‐twitch muscle units of the cat hindlimb pretibial flexors have been explored and related to normal locomotion. Tibialis anterior (TA) is parallel‐fibered and functionally crosses a single joint, the ankle, whereas extensor digitorum longus (EDL) is pinnate and spans the ankle, knee, metatarsophalangeal and interphalangeal joints. The active tetanic tension of TA remains near its peak value over a range of muscle lengths associated with normal ankle movement. In contrast, the length‐tension curve of EDL is sharply peaked. However, normal corollary action of the knee, ankle and metatarsophalangeal joints during stepping minimizes EDL's excursion and maintains it at or near a length optimal for peak tension development. EDL is capable of producing synchronous but sterotyped digit and ankle movements while TA provides for independent ankle flexion at all relevant joint angles. The mechanical properties of 84 TA and 98 EDL fast‐twitch muscle units were studied by measuring twitch contraction time (≤45 msec), peak tetanic tension, response to repetitive stimulation, and contractile fatigue resistance during electrical stimulation of single alpha axons, functionally isolated from ventral root filaments. These mechanical properties were essentially similar for both muscles with the exception of mean peak tetanic tension which was 30% lower for TA units (14 gm‐wt) than for EDL units (20 gm‐wt). A high proportion of units in both muscles demonstrated fatigue resistance which is reflective of the repetitive, phasic demand upon these muscles during locomotion.

Original languageEnglish (US)
Pages (from-to)23-37
Number of pages15
JournalJournal of Morphology
Volume153
Issue number1
DOIs
StatePublished - Jul 1977

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Developmental Biology

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