VALIDATION OF THE PHYSICAL WORKING CAPACITY AT THE FATIGUE THRESHOLD TREADMILL TEST

Abstract

The purposes of the present study were twofold: 1) to determine the physical working capacity at the fatigue threshold (PWCFT) during an incremental treadmill test, and 2) to examine the validity of this fatigue threshold through constant-velocity runs to exhaustion at 90, 100, and 110% of the estimated PWCFT. Twelve aerobically-trained males (mean age±SD=24.6±5.4 years, running volume=69.9±46.0 km·wk-1, n=9) and females (22.3±2.3 years, 45.6±4.6 km·wk-1, n=3) volunteered to perform a treadmill test to exhaustion with electromyographic (EMG) signals recorded from the m. vastus lateralis on four separate visits. The First visit required each subject to complete an incremental treadmill test to exhaustion for determination of their PWCFT. During the second, third, and fourth visit, the subjects completed a treadmill run to exhaustion at a constant velocity that corresponded to 90, 100, or 110% of their PWCFT in random order. The linear regression analyses indicated there were no significant (p>.05) changes in muscle activation (i.e. EMG amplitude) across time to exhaustion during the constant velocity runs at 90% (60.00±0.00 min) and 100% (48.86±14.59 min) PWCFT, but significant (p<.05) increases occurred at 110% PWCFT (19.44±10.26 min). Thus, the findings of the present study indicated that the PWCFT treadmill test was able to accurately estimate the fastest running velocity that could be maintained for an extended period of time without evidence of neuromuscular fatigue.

Key words: muscle activation, EMG amplitude, running, PWCFT