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Influence of countermovement depth on the countermovement jump-derived reactive strength index modified
Pérez-Castilla, Alejandro Weakley, Jonathon García-Pinillos, Felipe Rojas, F. Javier García-Ramos, Amador
Pérez-Castilla, Alejandro
Weakley, Jonathon
García-Pinillos, Felipe
Rojas, F. Javier
García-Ramos, Amador
Abstract
This study aimed to investigate the effect of countermovement depth on the magnitude of the countermovement jump (CMJ) derived reactive strength index modified (RSImod), and to compare the RSImod between the CMJ performed with a self-preferred knee flexion angle (CMJpref) and the CMJ performed from a pre-determined knee flexion angle (CMJrefer) with the countermovement depth more similar to the CMJpref. Sixteen subjects (11 males and 5 females; age 25.1 ± 6.3 years, body mass 69.7 ± 10.2 kg, body height 172.9 ± 8.1 m) randomly performed in a single session the CMJpref and CMJs from five pre-determined knee flexion angles (60°, 75°, 90°, 105°, and 120°). Our results showed that lower knee flexion angles were generally associated with greater RSImod values with the CMJ performed at 60° showing the greatest RSImod (P ≤ 0.049; effect size [ES] range = 0.19–0.63). The greatest RSImod for the CMJ performed at 60° was caused by the proportionally lower values of the time to take-off (ES range = 0.65–1.91) compared to the decrease observed in jump height (ES range = 0.11–0.25). The RSImod was higher for the CMJpref compared to the CMJrefer (P < 0.001; ES = 0.34) due to a higher jump height (P = 0.021; ES = 0.14) and reduced time to take-off (P < 0.001; ES = 0.85). These results indicate that practitioners should be careful when interpreting an individual’s changes in RSImod when the countermovement depth is not similar across the testing sessions. However, since the use of pre-determined knee flexion angles negatively impacts the RSImod, we encourage practitioners to use the CMJpref but only compare the RSImod when CMJs are performed using consistent countermovement depths.
Keywords
force platform, jump height, jumping ability, knee flexion angle, vertical jump
Date
2021
Type
Journal article
Journal
European Journal of Sport Science
Book
Volume
21
Issue
12
Page Range
1606-1616
Article Number
ACU Department
School of Behavioural and Health Sciences
Faculty of Health Sciences
Faculty of Health Sciences
Relation URI
Source URL
Event URL
Open Access Status
License
All rights reserved
File Access
Controlled