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Nonlinear force addition of newly recruited motor units in the cat hindlimb
Author(s) -
Clamann H. Peter,
Schelhorn Teresa B.
Publication year - 1988
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880111012
Subject(s) - motor unit , hindlimb , muscle contraction , motor unit recruitment , gastrocnemius muscle , anatomy , physics , mathematics , chemistry , materials science , physical medicine and rehabilitation , electromyography , medicine , skeletal muscle
The present experiments were designed to examine the interaction of simulaltaneoously active motor units. Pairs of medial gastrocnemius (MG) or soleus (Sol) units were stimulated individually and then together with constant frequency trains of 5–40 pulses per second. Stimulating two units asynchronously produced a smoother contraction than synchronous stimulation, but rarely a force increase. This contrasts with similar experiments on whole muscle bundles. A force increase may require that adjacent muscle fibers be active. The combined force to two motor units exceeded the algebraic sum of their separate forces by 12% in MG and 5% in Sol on average. The force a unit could sustain after a second unit fell silent was greater than the force the unit produced alone (21% in MG and 8% in Sol). We conclude that motor units produce more force when interacting than alone. During derecruitment the units remaining active produce more force than when recruited.