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1 Department of Integrative Physiology, University of Colorado, Boulder, CO, USA; Exercise Sceince Program, Department of Physical Therapy, Marquette University, Milwaukee, WI, USA
2 Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
* To whom correspondence should be addressed. E-mail: Sandra.Hunter{at}marquette.edu.
The purpose was to compare the time to task failure for a sustained isometric contraction performed at a submaximal intensity with the elbow flexor muscles by young and old men who were matched for strength. Eight young men (18-31 years) and 8 old men (67-76 years) sustained an isometric contraction at 20% of maximal voluntary contraction (MVC) torque until the target torque could no longer be achieved for at least 5 s. The maximal torque exerted at the wrist was similar for the young and old men before the fatiguing task (65.9 ± 8.0 N.m vs. 65.4 ± 8.7 N.m, P > 0.05) and they experienced similar reductions in MVC torque after the fatiguing contraction (31.4 ± 10.6%, P < 0.05). The time to task failure was longer for the old men (22.6 ± 7.4 min) compared with the strength-matched young men (13.0 ± 5.2 min, P < 0.05), despite each group sustaining a similar torque during the fatiguing contraction (P < 0.05). The increases in torque fluctuations, electromyographic (EMG) bursting activity, and heart rate were greater for young men compared with the old men, and were less at task failure for the old men (P < 0.05). Mean arterial pressure (MAP) increased at a similar rate for both groups of men (P > 0.05), whereas the averaged EMG activity and rating of perceived exertion (RPE) reached similar values at task failure for the young and old men (P > 0.05). These findings indicate that the longer time to task failure for the old men when performing the submaximal contraction was not due the absolute target torque exerted during the contraction.
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