Force developmental phase and reliability in explosive and voluntary grip exertions

The purposes of this study were to clarify the reliability of two types of grip exertions, explosive grip exertion and voluntary grip exertion up to t he maximal grip strength and to examine their force patterns using force-ti me parameters. Subjects were 100 healthy young male volunteers (age: 17.8 /-2.50 yr.) who had no upper limb injury. Grip strength was measured two ti mes with voluntary grip and then two times with explosive grip. 11 paramete rs derived from the force-time curve were selected to measure the developme ntal phase of muscle contraction. The reliability of maximal grip strength in explosive and voluntary grip exertions was very high (intraclass correla tion=.95, .93). The difference between two trials in explosive grip tended to be smaller than that for voluntary grip, and reliability of the exertion pattern was higher for explosive grip than voluntary grip. The times to re ach 90% of the maximal grip strength and the maximal grip strength in explo sive grip were shorter than those in voluntary grip. The other 8 force-time parameters had higher values in explosive grip than voluntary grip and hig her reliabilities. The force-time parameters reflect the properties of expl osive exertion. The results suggest the possibility that static explosive s trength could be evaluated using these force-time parameters.