Kryściak K, Celichowski J, Drzymała-Celichowska H, Gardiner PF, Krutki P. Force regulation and electrical properties of motor units in overloaded muscle.
Muscle Nerve 2015;
53:96-106. [PMID:
25900834 DOI:
10.1002/mus.24690]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2015] [Indexed: 11/08/2022]
Abstract
INTRODUCTION
The influence of long-term muscle overload on force regulation and electrical properties of motor units (MUs) was investigated in rats.
METHODS
Compensatory overload of the medial gastrocnemius was induced by tenotomy of its synergists. Electrophysiological experiments were performed on functionally isolated MUs 3 months after the surgery.
RESULTS
Force-frequency curves for overloaded MUs were shifted rightward compared with control, thus MUs developed the same relative tetanic forces at higher frequencies. Higher force increase was achieved in response to an increase in stimulation frequency in overloaded fast MUs compared with control. The optimal tetanic contraction, characterized by the highest force-time area per pulse, was evoked at higher stimulation frequencies for all overloaded MUs except FF. Only minor adaptive changes in MU action potentials occurred.
CONCLUSIONS
Compensatory muscle overload leads to substantial modifications in MU force development mechanisms, which are MU-type-specific and influence whole muscle force regulation.
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