Effects of a 5-week plyometric exercise program on vertical jump performance on rigid and sand surface

Szwajca, S., Stelzer, L., Zentgraf, K., Eils, E.

Zusammenfassung

INTRODUCTION: Plyometric training has demonstrated to be efficient in improving power-related measurements in athletic performance and muscle-tendon behaviour during stretch shortening cycle (SSC) exercise (Markovic, 2007; Hirayama et al., 2017). In handball, many actions require such attributes. Recently, beach handball was announced to be included into the Olympic Games and is currently, played by indoor handball players during their summer break. Although there are pronounced differences in playing on either rigid or sand ground, information regarding training to optimize performance for each format remains relatively unknown. Therefore, the aim of this study was to examine the effect of a 5-week plyometric exercise program on vertical jump performance on rigid and sand surface. METHODS: 22 participants (24±3yrs, 177.8±9.1cm, 77.7±11.6kg) were assigned into control (CON, n=9) or plyometric training (PT, n=13) group. While CON proceeded with their normal training routines, PT participated in a 5-week PT regime (2 sessions/week each 45 min) consisting of plyometric exercises on firm ground with a progressive increase in the number of jumps (from 80 to 180). Testing was con- ducted 48h before (pre) and after (post) PT regime on sand (s) and rigid (r) ground. Jump performance was investigated via vertical dis- placement of a back marker attached to the body (CMJ, DJ) and reactive strength index (DJ). Surface electromyography (sEMG) evaluation examined preactivation (PA) and short latency response (SLR) of tibialis anterior (TA), gastrocnemius medialis (GM), vastus medialis (VM) and biceps femoris (BF), and ratio of root-mean-square (rRMS) of (TA/GM) and (BF/VM) during DJ only. Magnitude-based inferences (MBI) were used to describe probabilities of substantial differences between conditions. RESULTS: There were observed improvements of 4.2%, 5.5% and 6.2% for CMJ (PT r), DJ (PT r) and RSI (PT s), respectively. However, no meaningful changes (possibly positive) were perceived in other performance variables. For sEMG, PA and SRL of TA, GM, BF and VM were deemed predominantly unclear pre to post. rRMS (BF/VM) was found likely and very likely positive for both groups and conditions (ES 0.66 to 1.71), whereas rRMS (TA/GM) was observed to be likely (ES -0.46) and very likely negative (ES -0.61) for PT on both conditions. CONCLUSION: A 5-week PT program on firm ground was not sufficient to markedly enhance vertical jump performance on sand surface in the PT group. Although co-activation of agonist/antagonist muscles was optimized, it remains unclear whether a PT performed on firm ground is practically relevant for indoor team handball players preparation due to negligible improvements in CMJ, DJ and RSI perfor- mance. In accordance with Binnie et al. (2014) we suggest that preparation on sand should be preferred as greater training adaptions to be achieved. REFERENCES: Binnie et al. (2014). J Sports Sci, 32(1), 8-15. Hirayama et al. (2017). Front Physiol, 8:16, 1-9. Markovic G. (2007). BJSM, 41(6), 349-355.