Related Experiment Video
Updated: May 17, 2026
Postural Organization of Gait Initiation for Biomechanical Analysis Using Force Platform Recordings
Published on: July 26, 2022
Changes in constraint of proximal segments effects time to task failure and activity of proximal muscles in knee
Peter C Poortvliet1, Kylie J Tucker, Paul W Hodges
1The University of Queensland, Centre for Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, Brisbane, Australia.
Objective:
Maintenance of a limb position against external load (position-control) fails earlier (time to task failure: TTF) than maintenance of identical force against rigid restraint (force-control). Although possibly explained by physiological differences between contractions, we investigated whether less constraint of movements in other planes and proximal segments (commonly less in position-control tasks) shortens TTF.
Methods:
Seventeen adults (32±7 years) contracted knee extensor muscles to task failure in a position-control task, with and without constraint of motion in other planes and proximal segments, and a force-control task with constraints. Electromyography of knee extensors, their antagonist and hip muscles was recorded with force/position.
Results:
TTF was shorter for position-control without (161±55 s) than with constraint (184±51 s). Despite identical constraint, TTF was shorter in position- than force-control (216±56 s). Muscle activity and position variability at failure was greater without constraint.
Conclusion:
Constraint of motion of proximal segments and other planes increases position-control TTF with less muscle activity and variability. As TTF differed between force- and position-control, despite equivalent constraint, other factors contribute to shorter position-control TTF.
Significance:
Results clarify that differences in the TTF between position- and force-control tasks are partly explained by unmatched restriction of motion in other planes and proximal segments.
