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F19U FREE COMMUNICATION/POSTER SKELETAL MUSCLE II

FATIGUE BREAKPOINT OF CONCENTRIC ISOKINETIC KNEE EXERCISE AND ITS RELATIONSHIP TO THE MECHANOMYOGRAPHIC SIGNAL

Schmitz, R J.1; Westwood, K C.1

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Medicine & Science in Sports & Exercise: May 2001 - Volume 33 - Issue 5 - p S262
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Mechanomyography (MMG) measures the oscillations of contracting skeletal muscle. This study examined the ability of MMG amplitude to predict the fatigue breakpoint of the knee extensors during isokinetic extension exercise. Ten subjects (5 males and 5 females) (age = 21.8 ± 4.3 yr, ht = 171.7 ± 8.4 cm, mass = 67.5 ± 12.1 kg) underwent isokinetic exercise (100 continual maximal effort contractions at 180°·sec−1. Peak torque (PT) and MMG signal from the vastus lateralis were collected simultaneously during the exercise protocol. The MMG signal was collected using standard piezoelectric crystal collection techniques. PT and MMG root mean square (rms) amplitude were calculated from each repetition of knee extension. Using regression techniques the breakpoints between the fatigue phase and the endurance phase of the isokinetic exercise for the PT and MMG rms amplitude data were calculated to be 32.5 ± 8.5 and 46.7 ± 16.1 contractions, respectively. There was no significant relationship between the PT and MMG rms amplitude over time (p>.05). However, during the fatigue phase (contractions 1 - 46) there was a significant correlation between PT and MMG rms amplitude (p < .05) R2 = 0.38). These results suggest that the rms amplitude of the MMG signal can predict fatigue in the vastus musculature during the initial (fatigue) phase of repeated high-velocity isokinetic exercise.

©2001The American College of Sports Medicine