Effect of Plyometric Training on Sand and Grass on the High Jumping Performance of Secondary School Volleyball Players.

Abstract

Developing jumping ability is important for volleyball performance, especially for young athletes who have limited physical size, which puts them at a disadvantage in competition.This research aimed to compare the effectiveness of plyometric training on sand versus grass surfaces on vertical jump performance in secondary school volleyball players.The study employed an experimental design with a sample of 20 male volleyball players aged 12-15 years from schools under the Lampang Primary Educational Service Area Office 3, Wang Nuea District, Lampang Province. Participants were simple randomly sampling by lottery into two equal groups of 10 players each: a sand-surface plyometric training group and a grass-surface plyometric training group. Both groups followed identical plyometric training programs comprising Multiple Box to Box Jump, Depth Jump, Jump and Reach, and Split Squat Jump exercises. The training program was divided into two phases: Phase 1 (1^st -4^th weeks) with 3 sets of 10 repetitions per exercise, and Phase 2 (5^th -8^th weeks) with 3 sets of 15 repetitions per exercise, with 2-minute rest periods between sets and 3-minute rest periods between exercises. Training sessions were conducted three times per week for 8 weeks. Vertical jump ability was measured by the Counter Movement Jump technique using a Vertec™ Vertical Jump Tester before and after the 8-week training program. Data were analyzed using Mann-Whitney U Test and Wilcoxon Signed Rank Test. Results showed no statistically significant differences between the two groups in baseline characteristics including age, weight, height, body mass index, and volleyball experience (p > 0.05). Pre-training vertical jump heights for the sand and grass training groups were not statistically different (37.90±11.37 and 42.50±6.55 centimeters, respectively, p > 0.05). After 8 weeks of training, both groups showed improvements in jump height, but there was no statistically significant difference between the groups (39.00±13.61 and 42.10±7.85 centimeters, respectively, p > 0.05). The changes in vertical jump ability following training did not differ significantly between the sand and grass training groups (1.10±3.11 and 0.04±2.67 centimeters, respectively, p = 0.280). The study concludes that 8 weeks of plyometric training on either sand or grass surfaces can improve vertical jump performance in volleyball players, with no significant difference between the two training surfaces. Therefore, coaches can select the training surface based on availability and contextual suitability without compromising the development of vertical jump ability in secondary school volleyball players.