Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions.

Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions. Research Abstract Details 

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Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions. Abstract Text:

B T Ballantyne,C G Kukulka,G L Soderberg,

Previous work on multifunctional muscle has suggested that motor unit recruitment during a combined force task is the result of an interactive effect of weighted inputs acting simultaneously on the motoneuron pool. The present study shows that a similar effect describes motor unit activation in a two-joint muscle as forces are combined at both proximal and distal attachments. The recruitment thresholds of single motor units in medial gastrocnemius muscle were determined during combined knee flexion and plantarflexion isometric contractions. Slow isometric ramp contractions in knee flexion were produced while maintaining various background levels of plantarflexion force. The combination of knee flexion and plantarflexion forces at which a motor unit initially discharged was used to characterize recruitment as represented by the slope of the regression line fit to the individual data points. Each subject completed two experiments; one at each of two knee joint angles, with the ankle joint fixed at 90 degrees. The effect of knee angle was assessed by comparing the slopes of the regression lines that characterized motor unit recruitment at each knee angle. Motor units in medial gastrocnemius were recruited when the linear sum of the forces exerted in plantarflexion and knee flexion exceeded a certain threshold of combined force. Specifically, the apparent force threshold of recruitment in knee flexion decreased as the level of force maintained in plantarflexion increased. Further, evidence is provided indicating that the linear relationship describing recruitment in two-joint muscle is dependent upon joint angle.(ABSTRACT TRUNCATED AT 250 WORDS)

Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions. Publishing Authors By Initials

BT Ballantyne,CG Kukulka,GL Soderberg,

For similar musculoskeletal, neural, and ocular physiology: nervous system physiology: nervous system physiologic processes: neural conduction: recruitment, neurophysiological research abstracts see: musculoskeletal, neural, and ocular physiology: nervous system physiology: nervous system physiologic processes: neural conduction: recruitment, neurophysiological research

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Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions. Journal Published:

PUBLICATION TYPE: Research Support, U.S. Gov't,

Journal: Experimental brain research. Experimentelle Hirnfo

VOLUME: 93

Page Numbers: 492-8

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ISSN: 0014-4819

DAY: 15

MONTH: 02

YEAR: 1993

Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions. Information

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LANGUAGE: eng

NlmUniqueID: 43312

Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions. Keywords Mesh Terms:

KEYWORDS: Recruitment, Neurophysiological

MESH TERMS: physiology

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Grant and Affiliation Information for Motor unit recruitment in human medial gastrocnemius muscle during combined knee flexion and plantarflexion isometric contractions.

AFFILIATION: Physical Therapy Graduate Program, University of Iowa, Iowa City 52242.

Country: GERMANY

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MEDLINETA: Exp Brain Res

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