A-40 Free Communication/Poster - Fitness Assessment Strategies for Children and Adolescents

Abstract

PURPOSE: The purposes of the present study were twofold: 1) to determine if the model used for estimating the physical working capacity at the fatigue threshold (PWCFT) during incremental cycle ergometry could be applied to treadmill running to derive a new neuromuscular fatigue threshold, and 2) to compare the running velocities associated with the PWCFT, ventilatory threshold (VT), and respiratory compensation point (RCP). METHODS: Fifteen moderately-trained males and females (mean age ± SD = 21.5 ± 1.3 yrs; 68.7 ± 10.5 kg; 175.9 ± 6.7 cm) volunteered to perform an incremental treadmill test that began at 6.0 mph (1% grade) and increased 1.0 mph every two minutes until volitional fatigue. Expired gas samples were collected for the determination of VT and RCP. During each 2-min stage of the test, six, 10-second electromyographic (EMG) samples were recorded from the vastus lateralis. The EMG amplitude (μVrms) values were calculated for each 10-second epoch and separately plotted across time for each stage (i.e. running velocity) of the test. The PWCFT was then determined by averaging the highest running velocity that resulted in a non-significant (P > 0.05) slope coefficient for the EMG amplitude versus time relationship, with the lowest running velocity that resulted in a significant (P < 0.05) positive slope coefficient. RESULTS: The one-way ANOVA with repeated-measures and post-hoc analyses indicated there were significant mean differences in running velocities between the VT (7.0 ± 0.8 mph) and PWCFT (8.7 ± 1.4 mph), and the VT and RCP (8.7 ± 1.1 mph), but not between the PWCFT and RCP. In addition, there were significant zero-order correlations for VT versus PWCFT (r = 0.70), RCP versus PWCFT (r = 0.70), and VT versus RCP (r = 0.91). CONCLUSIONS: The findings of the present study indicated that the PWCFT model used to estimate the onset of neuromuscular fatigue during cycle ergometry could be applied to incremental treadmill running. Theoretically, the PWCFT treadmill test estimates the maximal running velocity that can be sustained for an extended period of time without fatigue-induced increases in muscle activation. The present findings also indicated that the PWCFT and RCP occurred at the same exercise intensity (i.e. running velocity) and thus, may be related to a common physiological mechanism of fatigue.