Journal article
Muscle activity differs with load compliance during fatiguing contractions with the knee extensor muscles
Experimental brain research, Vol.203(2), pp.307-316
06/2010
DOI: 10.1007/s00221-010-2233-3
PMID: 20358188
Abstract
The purpose of this study was to determine the influence of load compliance on the time to failure and rate of change in electromyographic (EMG) activity when the knee extensor muscles performed fatiguing contractions against submaximal loads. The low-compliance condition required the subject to exert a force against a rigid restraint (force control), whereas the high-compliance condition involved maintaining the knee joint angle while supporting an equivalent inertial load (position control). Both contractions were sustained for as long as possible. Each subject exerted a similar net torque about the knee joint during the force and position tasks; the target force corresponded to a force at the ankle equal to 20% of the maximal voluntary contraction (MVC) force. Thirteen healthy adults (25 +/- 7 year) participated in the study. MVC forces before the force and position tasks were similar (189 +/- 40 N vs. 179 +/- 43 N, P = 0.4), and the target force was 36 +/- 8 N. The time to task failure was longer for the force task (224 +/- 114 s) than for the position task (110 +/- 36 s, P < 0.05), but MVC force declined to a similar level immediately after task failure for the two tasks (-31 +/- 16%). The briefer time to failure for the position task was accompanied by greater rates of increase in agonist EMG amplitude and the pressor response. Coactivation ratios, in contrast, were similar for the two tasks and did not contribute to task differences in time to failure. These findings indicate that it was more difficult to sustain a submaximal contraction with the knee extensor muscles when the task required position control, despite comparable net muscle torques for the low- and high-compliance tasks.
Details
- Title: Subtitle
- Muscle activity differs with load compliance during fatiguing contractions with the knee extensor muscles
- Creators
- Thorsten Rudroff - Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA. thorsten.rudroff@colorado.eduJamie N JusticeStephen MatthewsRena ZuoRoger M Enoka
- Resource Type
- Journal article
- Publication Details
- Experimental brain research, Vol.203(2), pp.307-316
- Publisher
- Germany
- DOI
- 10.1007/s00221-010-2233-3
- PMID
- 20358188
- ISSN
- 0014-4819
- eISSN
- 1432-1106
- Grant note
- NS043275 / NINDS NIH HHS
- Language
- English
- Date published
- 06/2010
- Academic Unit
- Neurology; Health and Human Physiology
- Record Identifier
- 9984002490502771
Metrics
26 Record Views