Citation

Griffith EE, Yoon T, Hunter SK. J. Appl. Physiol. (APS Bethesda) 2010; 108(6): 1510-1519.

Affiliation

Marquette University.

Copyright

(Copyright © 2010, American Physiological Society)

DOI

10.1152/japplphysiol.01396.2009

PMID

20299610

Abstract

The purpose was to compare the time to failure and muscle activation of young and old adults for a sustained isometric submaximal contraction with the dorsiflexor muscles when the foot was restrained to a force transducer (force-control task) compared with supporting an equivalent inertial load unrestrained in the sagittal plane (position-control task). Seventeen young adults (23.6 +/- 6.5 yrs) and 12 old adults (70.0 +/- 5.0 yrs) performed the force-control and position-control tasks at 30% maximal voluntary contraction (MVC) until task failure on separate days. Despite the similar load torque for each task, the time to failure for the force-control task was longer than the position-control task (10.4 +/- 4.5 min vs 8.6 +/- 3.4 min, respectively; P = 0.03) for both the young and old adults. The old adults however, had a longer time to task failure than the young adults for both tasks (11.4 +/- 4.4 min vs. 8.1 +/- 2.1 min, respectively; P = 0.01) with no interaction of age and task (P = 0.83). The rate of increase in agonist and antagonist RMS EMG, agonist EMG bursting activity, mean arterial pressure and heart rate during the fatiguing contraction was greater for the position-control task than the force-control task for both the young and old adults. The old adults had a less rapid rate of increase in EMG activity, fluctuations in motor output and cardiovascular measures compared with the young adults for both tasks. Development of fatigue can be manipulated in both young and old adults by providing greater support to the foot during daily and ergonomic tasks that require prolonged activation of the lower leg. Minimizing load compliance to only one degree of freedom during a position-control task maintained the greater fatigue resistance with age for an isometric contraction. Key words: muscle fatigue, tibialis anterior, dorsiflexion, aging.

Language: en