Variation in limb support influences the time to task failure for a postural contraction.
The authors compared the time to task failure and muscle activation for a sustained isometric submaximal contraction with the dorsiflexor muscles when the support of the foot varied while supporting an inertial load (position task). Participants performed a supported position task (n = 8) or an unsupported position task (n = 15) while maintaining a constant angle at the ankle with an inertial load equivalent to 20% of maximal isometric contraction torque until task failure. The time to failure for the supported position task (M = 15.4 min, SD = 6.8 min) was longer than for the unsupported position task (M = 10.0 mn, SD = 6.2 min, p = .01). Electromyographic activity of the tibialis anterior differed between tasks (Session x Time, p = .028). Increasing foot support during a position task decreased muscle fatigability and altered activation of the primary agonist indicating the importance of limb support to minimize fatigue during prolonged activation of the dorsiflexor muscles.
Yoon
Tejin
T
Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, WI 53201, USA.
Hawe
Rachel
R
Hunter
Sandra K
SK
D000293:Adolescent; D000328:Adult; D001915:Braces; D004576:Electromyography; D005260:Female; D005528:Foot / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007866:Leg / Q000502:physiology; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology; D016059:Range of Motion, Articular; D012016:Reference Values; D013647:Task Performance and Analysis; D013997:Time Factors; D016474:Weight-Bearing; D055815:Young Adult