Kinematic and Neuromuscular Measures of Intensity During Plyometric Jumps

Abstract

The aim of this study was to assess jumping performance and neuromuscular activity in lower limb muscles after drop jumps (DJ) from different drop heights (intensity) and during continuous jumping (fatigue), using markers such as reactive strength, jump height, mechanical power and surface electromyography (sEMG). The eccentric (EC) and concentric (CON) sEMG from the medial gastrocnemius (MG), biceps femoris (BF) and rectus (R) muscles were assessed during all tests. In a cross-sectional, randomized study, eleven volleyball players (age 24.4±3.2 years) completed 20 to 90-cm (DJ20 to DJ90) drop jumps and a 60-s continuous jump test. A one-way ANOVA test was used for comparisons, with Sidak post-hoc. The α level was <0.05. Reactive strength was greater for DJ40 compared to DJ90 (p<0.05; ES: 1.27). Additionally jump height was greater for DJ40 and DJ60 compared to DJ20 (p<0.05; ES: 1.26 and 1.27, respectively). No clear pattern of neuromuscular activity appeared during DJ20 to DJ90: some muscles showed greater, lower, or no change with increasing heights for both agonist and antagonist muscles, as well as for eccentric and concentric activity. Mechanical power, but not reactive strength, was reduced in the 60-s jump test (p<0.05; ES: 3.46). No changes were observed in sEMG for any muscle during the eccentric phase nor for the R muscle during the concentric phase of the 60-s jump test. However, for both MG and BF, concentric sEMG was reduced during the 60-s jump test (p<0.05; ES: 5.10 and 4.61, respectively). In conclusion, jumping performance and neuromuscular markers are sensitive to DJ height (intensity), although not in a clear dose-response fashion. In addition, markers such as mechanical power and sEMG are especially sensitive to the effects of continuous jumping (fatigue). Therefore, increasing the drop height during DJ does not ensure a greater training intensity and a combination of different drop heights may be required to elicit adaptations.

Effects of Relative Drop Heights of Drop Jump Biomechanics in Male Volleyball Players

“…Therefore, 100 %CMJH may be the turning point for any observed biomechanical changes in the relative drop heights for DJ plyometric training intensity. These findings were similar to previous investigations from absolute drop heights that reported both rapid and powerful DJ performance increased from 35- [37] and 40-cm [38,39] and reported those as the turning point compared to greater heights. Larger drop heights may lead to decrements of DJ performances due to a reduction from the SSC, which might be a protective strategy for preventing muscle and tendon injury associated with a higher impact GRF [8,9,19].…”

“…The DJ performance remained unchanged with incremental drop heights in the current study, which agreed with Bassa et al [40] and Bencke et al [41] but contrasted with Prieske et al [37], Andrade et al [38] and Lesinski et al [39]. Prieske et al [37] reported that both the DJH and RSI increased with drop heights from 20-to 50-cm and from 20-to 35-cm, respectively, in 239 adolescent handball players, irrespective of sex.…”

“…Further, they showed that the 50-cm drop-height induced additional increments to the DJH but at the expense of ground contact time, therefore, reducing RSI. Andrade et al [38] and Lesinski et al [39] reported using a drop height of 40-cm resulted in the greatest RSI. The discrepancy in these findings may be attributed to the number of participants, biodiversity of participants and their DJ technique between investigations.…”

Optimal Reactive Strength Index: Is It an Accurate Variable to Optimize Plyometric Training Effects on Measures of Physical Fitness in Young Soccer Players?

“…Athletes from the OPT group performed maximal-effort vertical-oriented drop jumps from an individualized box height to allow the achievement of optimal reactive strength. Individualization of box heights for the athletes in the OPT group was according to protocols previously described (3,22). Briefly, all athletes were asked to perform a maximal-effort vertical-oriented drop jump from fixed box heights of 10-cm, 20-cm, 30-cm, 40-cm, and 50-cm.…”

“…However, although power output and reactive strength index (RSI) may augment with initial increases in drop height, if height continues to increase the jump performance may be impaired (22). Moreover, increasing the drop height during drop jumps does not ensure greater electromyographic responses in all targeted muscle groups (3). Thus, the use of "optimal drop heights" based on the highest RSI values have been suggested as a simple and effective way to prescribe plyometric training routines (22).…”