Evaluation Of Stretch Shortening Cycle Performance Of Upper Limbs

PURPOSE: The purpose of this study was to suggest an indicator for the Rebound Jump-index (RJ-index) of upper limbs that reflects the Stretch-Shortening Cycle performance (SSC performance) of the upper limbs, and elucidate the inter-trial reliability and the criterion-related validity of this indicator. METHODS: The subjects were 31 male university track-and-field athletes between the ages of 18 and 21 years. Using an optical sensor, five rebound jumps with the upper limbs were performed on-site, and a jump height derived from the ground contact time and airborne time was calculated. The jump height was further divided by the ground contact time, and treated as the RJ-index of the upper limbs. For the rebound jumps, we instructed the subjects to keep their elbows as straight as possible during ground contact, keep the ground contract time short, and jump high. At the start of measurement, the hip joint angle was fixed to be 0°, and both upper limbs were kept perpendicular to the floor. In order to verify the reproducibility (inter-trial reliability) of the RJ-index measurement values of the upper limbs, we performed the same measurements 2 weeks later and derived the intraclass correlation coefficients (ICC) between the measurement values. In addition, To assess the criterion-related validity of the RJ-index of the upper limbs, we performed to the correlation between the RJ-index measurement and the shot put records. RESULTS: ICC (1,1) between the RJ-index measurement of upper limbs (0.19+0.07) and the re-measurement (0.18+0.08) was ρ=0.83, and ICC (1,2) was ρ=0.91. These values indicate that the measurement reproducibility was relatively high. Upon deriving the partial correlation coefficient assuming age and weight as control variables, a relatively high correlation was seen between the RJ-index of the upper limbs and the shot put records (r=0.59, p<0.01). CONCLUSIONS: Therefore, we think that it is apparent that the RJ-index of the upper limbs had a definite inter-trial reliability and this test may possibly have criterion-related validity as an assessment test for SCC performance of the upper limbs.