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A multimuscle state analysis of adult motor learning

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A multimuscle state analysis of adult motor learning. / Spencer, John P.; Thelen, Esther.

In: Experimental Brain Research, Vol. 128, No. 4, 1999, p. 505-516.

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Spencer, John P. ; Thelen, Esther. / A multimuscle state analysis of adult motor learning. In: Experimental Brain Research. 1999 ; Vol. 128, No. 4. pp. 505-516.

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@article{e669f50d883842838679a27e6d9a58c9,
title = "A multimuscle state analysis of adult motor learning",
abstract = "We introduce a new EMG state analysis to test two competing hypotheses about the role of muscle coactivity in learning a complex, multijoint reaching movement. Following Bernstein, one hypothesis is that as a task is learned, coactivity should decrease as degrees of freedom are released and limb stiffness is reduced. An alternative hypothesis is that as movement speed increases with learning, muscle coactivity should increase, possibly to stabilize joints against high inertial forces. Three participants performed a vertical reaching movement identical to that used by Schneider et al. We monitored the activity of four arm and shoulder muscles as participants completed 100 practice trials. Each frame of EMG activity was assigned to one of 16 possible combinations of the four monitored muscles based on an on-off activation threshold. This analysis yielded a time-based summary of muscle coactivity during the movement and across practice trials. Results of the state analysis supported the second hypothesis. As participants decreased their movement times over practice, coactivity increased - participants used more three- and four-muscle coactivity states. Changes were especially dramatic during the braking phase of the Up and Down portion of the vertical movement. When participants performed deliberately slow movements after speeded practice, three- and four-muscle coactivity was suppressed. We suggest that increased use of muscle coactivity may serve to counteract unwanted rotational forces generated during fast movements.",
keywords = "EMG, Motor learning, Movement speed, Muscle coactivity",
author = "Spencer, {John P.} and Esther Thelen",
year = "1999",
doi = "10.1007/s002210050873",
language = "English",
volume = "128",
pages = "505--516",
journal = "Experimental Brain Research",
issn = "0014-4819",
publisher = "Springer",
number = "4",

}

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TY - JOUR

T1 - A multimuscle state analysis of adult motor learning

AU - Spencer, John P.

AU - Thelen, Esther

PY - 1999

Y1 - 1999

N2 - We introduce a new EMG state analysis to test two competing hypotheses about the role of muscle coactivity in learning a complex, multijoint reaching movement. Following Bernstein, one hypothesis is that as a task is learned, coactivity should decrease as degrees of freedom are released and limb stiffness is reduced. An alternative hypothesis is that as movement speed increases with learning, muscle coactivity should increase, possibly to stabilize joints against high inertial forces. Three participants performed a vertical reaching movement identical to that used by Schneider et al. We monitored the activity of four arm and shoulder muscles as participants completed 100 practice trials. Each frame of EMG activity was assigned to one of 16 possible combinations of the four monitored muscles based on an on-off activation threshold. This analysis yielded a time-based summary of muscle coactivity during the movement and across practice trials. Results of the state analysis supported the second hypothesis. As participants decreased their movement times over practice, coactivity increased - participants used more three- and four-muscle coactivity states. Changes were especially dramatic during the braking phase of the Up and Down portion of the vertical movement. When participants performed deliberately slow movements after speeded practice, three- and four-muscle coactivity was suppressed. We suggest that increased use of muscle coactivity may serve to counteract unwanted rotational forces generated during fast movements.

AB - We introduce a new EMG state analysis to test two competing hypotheses about the role of muscle coactivity in learning a complex, multijoint reaching movement. Following Bernstein, one hypothesis is that as a task is learned, coactivity should decrease as degrees of freedom are released and limb stiffness is reduced. An alternative hypothesis is that as movement speed increases with learning, muscle coactivity should increase, possibly to stabilize joints against high inertial forces. Three participants performed a vertical reaching movement identical to that used by Schneider et al. We monitored the activity of four arm and shoulder muscles as participants completed 100 practice trials. Each frame of EMG activity was assigned to one of 16 possible combinations of the four monitored muscles based on an on-off activation threshold. This analysis yielded a time-based summary of muscle coactivity during the movement and across practice trials. Results of the state analysis supported the second hypothesis. As participants decreased their movement times over practice, coactivity increased - participants used more three- and four-muscle coactivity states. Changes were especially dramatic during the braking phase of the Up and Down portion of the vertical movement. When participants performed deliberately slow movements after speeded practice, three- and four-muscle coactivity was suppressed. We suggest that increased use of muscle coactivity may serve to counteract unwanted rotational forces generated during fast movements.

KW - EMG

KW - Motor learning

KW - Movement speed

KW - Muscle coactivity

UR - http://www.scopus.com/inward/record.url?scp=0032834749&partnerID=8YFLogxK

U2 - 10.1007/s002210050873

DO - 10.1007/s002210050873

M3 - Article

C2 - 10541744

AN - SCOPUS:0032834749

VL - 128

SP - 505

EP - 516

JO - Experimental Brain Research

JF - Experimental Brain Research

SN - 0014-4819

IS - 4

ER -

ID: 64348441