Effect of teeth clenching on muscle strength during repeated isokinetic knee extensions

Abstract

The purpose of this study was to investigate the effect of teeth clenching on isokinetic knee extension force during repeated voluntary contractions. We assessed isokinetic muscle strength in association with teeth clenching during 100 consecutive knee extensions at 60 degrees per second (deg/s) using a Cybex 6000 isokinetic dynamometer. In this study, 8 healthy male volunteers (28.4 ± 3.89 years) were asked to perform isokinetic contractions in an extended cycle of five contractions without teeth clenching followed by five contractions with the teeth clenching. The peak torque per body weight was statistically analyzed. In our results, the peak torque per body weight with teeth clenching were significantly greater than those without teeth clenching in the first 70 cycles ; however, no significant differences were shown at 71 ∼ 100 cycles. There was a significant negative correlation between the number of knee extensions and the difference in peak torque per body weight derived from with and without teeth clenching (r=-0.475, p<0.0001). Our findings reveal that the effect of teeth clenching on the isokinetic muscle strength of knee extension is dependent on muscular fatigue, and that the improving effect of teeth clenching on isokinetic muscle strength declines with increasing muscular fatigue.