Comparing the effects of akimbo and bent-in-front arm positions on jump metrics : Validity and reliability of a modified 10/5 repeated jump test

The purpose of this study was to compare the effects of two arm positions, akimbo and the newly introduced bent-in-front, on jump metrics in the ten-to-five repeated jump test (10/5 RJT) and to evaluate the reliability and validity of new modified bent-in-front variation. In contrast to akimbo, bent-in-front arm variation allows participants to use their arms freely by holding them with free hands, with parallel arms bent in front of chest and elbows pointing downward without swinging. This new arm position was designed to alleviate postural control difficulties and ensure smooth movement during repeated jumps on the force plate. However, the 10/5 RJT was designed to measure lower-body stretch–shortening cycle (SSC) performance, and it is unknown whether the bent-in-front arm variation would affect jump performance, such as arm swing. If the arms can be freed without interfering with jump performance, it would be possible to determine lower-body SSC performance without the contribution of the arms and have the advantage of postural control assistance. Fifty-five healthy sports science students who regularly participated in intercollegiate or recreational sports performed 10/5 RJT with arms akimbo and bent-in-front during two sessions. Four jump metrics, including the reactive strength index, and four reliability and validity statistics, including intraclass-correlation-coefficients, were estimated. The results indicated no significant differences in the jump metrics between two arm variations. Bent-in-front arm variation can be deemed as a valid and reliable test. Therefore, the newly introduced 10/5 RJT with arms bent-in-front can be used to evaluate SSC performance in this cohort.