Effect of teeth clenching on isometric and isokinetic strength of ankle plantar flexion

To investigate the effect of voluntary teeth clenching on the isometric and isokinetic exercises of the lower limbs, the association of muscle strength (peak torque, PT) and muscle activities (integrated electromyographic activity per unit of time, iEMG/s) of the three muscles of the triceps surae with teeth clenching during isometric and isokinetic plantar flexion were simultaneously measured for 12 healthy male volunteers using a Cybex 6000 Extremity Testing and Rehabilitation System and a surface EMG analyzing system. The statistical analysis demonstrated that for the isometric exercise, PT and each iEMG/s significantly increased in association with teeth clenching, and a positive correlation existed between the biting force and each variable. In contrast, no association was found with teeth clenching for the isokinetic exercise. In this study, therefore, it was found that the effect of teeth clenching differed between the isometric and isokinetic exercises.