Test–retest reliability of drop jumps in students aged seven and eight: exploratory investigation

Purpose: The drop jump test has been widely used for adolescent and adult athletes to monitor improvements in reactive strength index. However, little research has examined the use or reliability of drop jumps assessment with primary school children. Therefore, we aimed to assess the test–retest reliability of reactive strength index (RSI) tests in healthy physical education students within the primary school setting. Methods: Twelve students (six females and six males) aged seven and eight years were tested in two sessions one week apart. Familiarization sessions took place before the main trials. The test protocol included drops jumps from 10 cm, 20 cm and 30 cm box heights and RSI was calculated by dividing jump height (cm) by contact time (s). Results: Good to excellent intra-session reliability (intraclass correlation coefficient ≥ 0.80) was noted at both testing sessions for the RSI obtained after drop jumps from 10, 20, 30 cm box heights. The intersession reliability for drop jumps from all heights was high, with no significant difference between the two sessions (r = 0.81–0.97, p = 0.30–0.94). Conclusion: RSI assessment through low–moderate drop jump heights shows good potential to be a reliable method. Current findings could be of value to teachers assessing the effectiveness of resistance training movement activities in the physical education program