Author(s): OZGOR, N., AYTAC, T., KOSE, M.G., KIN ISLER, A., Institution: BAŞKENT UNIVERSITY, Country: TURKEY, Abstract-ID: 2211

INTRODUCTION:
Gymnastics requires repeated jumping, landing and precise neuromuscular control. The drop jump (DJ) is commonly used to assess reactive performance because it involves short ground contact times and effective use of the stretch-shortening cycle (Wilder et al., 2021). The reactive strength index (RSI), calculated as jump height divided by contact time, is a key indicator of DJ performance. Although drop height affects neuromuscular and mechanical responses, the optimal DJ height in young gymnasts has not been clearly established (Moir et al., 2022). Therefore, this study aimed to determine optimal bilateral and unilateral DJ heights in young female gymnasts.
METHODS:
Twenty-two young female gymnasts (11.1 +/- 1.5 years, range 9-14) participated. Following anthropometric assessment, bilateral DJs were performed from 20, 30 and 40 cm, and unilateral DJs from 10 to 30 cm in 5 cm increments (Bassa et al., 2012). Participants kept their hands on their hips and were instructed to minimize ground contact time while maximizing jump height. Two trials per height were completed and the best trial was used for analysis. Jump height was calculated from flight time, and RSI was computed as jump height divided by contact time (Bishop et al., 2019). Optimal height was defined as the condition with the highest RSI (Byrne et al., 2017). For unilateral analysis, the limb with the higher mean RSI across all heights was classified as the strongest limb, while the contralateral limb was defined as the weakest.
RESULTS:
The effect of drop height on reactive strength index (RSI) was examined using repeated-measures ANOVA. For bilateral drop jumps (20, 30 and 40 cm), no significant main effect of height was observed (F(2,42) = 0.55, p = 0.582, eta p2 = 0.03), although the highest mean RSI was recorded at 30 cm. In contrast, a significant main effect of height was found for unilateral drop jumps in the strongest limb (10-30 cm) (F(4,84) = 4.38, p = 0.003, eta p2 = 0.17). Post-hoc comparisons (Bonferroni) indicated that RSI at 10 cm was significantly greater than at 20, 25 and 30 cm (p < 0.05). A similar significant effect was observed for the weakest limb (F(4,84) = 5.08, p = 0.001, eta p2 = 0.19), with RSI at 10 cm significantly greater than at 30 cm (p = 0.026). These findings suggest that bilateral RSI is relatively stable across heights, whereas unilateral reactive performance is optimized at lower drop heights, particularly 10 cm.
CONCLUSION:
These results demonstrate that drop height does not significantly influence bilateral RSI within the tested range in young female gymnasts, although the highest mean value was observed at 30 cm, suggesting potential practical relevance. However, unilateral reactive performance is clearly height-dependent, with optimal values observed at 10 cm. Therefore, lower unilateral drop heights should be considered when assessing and prescribing reactive strength training in this population.