Relationship Between Drop Jump Training–Induced Changes in Passive Plantar Flexor Stiffness and Explosive Performance

Abstract

Passive muscle stiffness is positively associated with explosive performance. Drop jump training may be a strategy to increase passive muscle stiffness in the lower limb muscles. Therefore, the purpose of this study was to examine the effect of 8-week drop jump training on the passive stiffness in the plantar flexor muscles and the association between training-induced changes in passive muscle stiffness and explosive performance. This study was a randomized controlled trial. Twenty-four healthy young men were divided into two groups, control and training. The participants in the training group performed drop jumps (five sets of 20 repetitions each) 3days per week for 8weeks. As an index of passive muscle stiffness, the shear moduli of the medial gastrocnemius and soleus were measured by shear wave elastography before and after the intervention. The participants performed maximal voluntary isometric plantar flexion at an ankle joint angle of 0° and maximal drop jumps from a 15cm high box. The rate of torque development during isometric contraction was calculated. The shear modulus of the medial gastrocnemius decreased for the training group (before: 13.5±2.1kPa, after: 10.6±2.1kPa); however, such a reduction was not observed in the control group. There was no significant group (control and training groups)×time (before and after the intervention) interaction for the shear modulus of the soleus. The drop jump performance for the training group improved, while the rate of torque development did not change. Relative changes in these measurements were not correlated with each other in the training group. These results suggest that drop jump training decreases the passive stiffness in the medial gastrocnemius, and training-induced improvement in explosive performance cannot be attributed to change in passive muscle stiffness.

The Influence of Daily Exercise on Muscle Echo Intensity and Stiffness in Young Women

“…For instance, Mannarino et al [32] observed an increase in the shear modulus of the VL after eight weeks of resistance training. Contrary to this finding, Ando et al [33] showed a significantly decrease in MG shear modulus after the same duration of drop jump training. More interestingly, muscle stiffness had a positive correlation with sprint performance and a negative correlation with endurance performance [14] implying that the physiological importance of muscle stiffness differs depending on exercise type.…”

Effects of Plyometric Jump Training on the Reactive Strength Index in Healthy Individuals Across the Lifespan: A Systematic Review with Meta-analysis

“…1 for exclusion reasons). Finally, 61 studies were considered eligible for this meta-analysis [ 19 , 25 , 87 – 145 ], of which 60 were written in English, and one in German [ 144 ].…”

“…Nonetheless, studies included in this meta-analysis that applied different PJT frequencies also applied a different total number of jumps. For example, one study applied three weekly PJT sessions over a period of 8 weeks [ 87 ] with an RSI improvement of ~ 54% after a total of 2400 jumps. In contrast, another study [ 90 ] applied two weekly PJT sessions over a period of 8 weeks, with a RSI improvement of ~ 20% after a total of 660 jumps.…”

The relationship between elastography-based muscle properties and vertical jump performance, countermovement utilization ratio, and rate of force development

“…Contrary to our findings, a previous study also reported a positive association between gastrocnemius shear modulus and drop jump performance (Ando et al 2021a ). Interestingly, gastrocnemius shear modulus however decreased after a drop-jump training intervention (Ando et al 2021b ), without concomitant changes in RFD. Considering the participants in that study were not trained athletes, the authors suggested that drop jump training could enforce lengthening of muscles fascicles, which could result in decreased shear modulus at a given muscle length by altering the length-tension relationship and thus leading to less passive tension at a given muscle length (Brughelli and Cronin 2007 ).…”