Phase-Specific Predictors of Countermovement Jump Performance That Distinguish Good From Poor Jumpers

Abstract

Krzyszkowski, J, Chowning, LD, and Harry, JR. Phase-specific predictors of countermovement jump performance that distinguish good from poor jumpers. J Strength Cond Res 36(5): 1257-1263, 2022-The modified-reactive strength index (RSImod) is commonly examined during the countermovement vertical jump (CMJ) to assess neuromuscular characteristics (i.e., explosiveness, fatigue, adaptation, etc.) of an athlete. However, both phase-specific variables explaining RSImod and corresponding differences between good and poor jumpers are not well understood in trained populations. This study sought to (a) identify predictors of RSImod during the CMJ based on phase-specific temporal and rate of force development (RFD) variables, and (b) identify differences in those predictors between performers with high and low RSImod performances from a sample of collegiate male basketball players (n 5 22; 20 6 2 years; 1.99 6 0.06 month; 93.8 6 7.5 kg). Subjects performed 3 maximal effort CMJ trials while ground reaction force data was recorded using 2 force platforms. Phase-specific temporal and RFD variables were calculated and entered into separate stepwise regression models using backward elimination to identify predictors RSImod. Individuals were then categorized into high (n 5 11; RSImod 5 0.68 6 0.10) and low (n 5 11; RSImod 5 0.48 6 0.04) RSImod groups according to the overall median RSImod (RSImod 5 0.55). Independent t-tests (a 5 0.05) were conducted and supplemented by Cohen's d effect sizes (d $ 1.2, large) to compare groups relative to significant predictors identified by the linear regression models and related variables. The temporal regression model (R 2 5 0.530) retained unloading time and concentric time, whereas the RFD regression model (R 2 5 0.429) retained unloading RFD and braking RFD. The high RSImod group exhibited significantly greater RSImod scores (d 5 2.51, p , 0.001) and jump heights (d 5 1.58, p , 0.001), shorter times to takeoff (d 5 1.27, p 5 0.007) and concentric times (d 5 1.51, p 5 0.002), and a greater braking RFD (d 5 1.41, p 5 0.005) than the low RSImod group. Individuals targeting enhanced CMJ performance may consider exploring strategies or interventions to develop quicker unloading and concentric phases and increasing eccentric RFD abilities.

Movement competency and measures of isometric and dynamic strength and power in boys of different maturity status

“…This explanation is supported by the significantly greater RSI mod observed by the post‐PHV group over both the pre‐ and circa‐PHV cohorts despite having a greater time to takeoff. Higher RSI mod values typically reflect explosive jump performance and are characterized by greater absolute force, power, and velocity within the eccentric phase 39 . Therefore, the data indicate that maturity improves the eccentric phase‐specific qualities relevant to CMJ performance.…”

“…Higher RSI mod values typically reflect explosive jump performance and are characterized by greater absolute force, power, and velocity within the eccentric phase. 39 Therefore, the data indicate that maturity improves the eccentric phase-specific qualities relevant to CMJ performance.…”

Factors influencing optimum countermovement jump performance and movement strategy in Championship professional football players: implications for player profiling

“…McMahon et al (2017b) used the modified reactive-strength index defined as the ratio of jump height and time to take-off (as opposed to the flight time:contraction time ratio used in the present study), observing that better performance was associated with greater peak force, peak power, and peak velocity in the eccentric and concentric phases of double-legged CMJ. Krzyszkowski et al (2020) used the same outcome measure and employed a similar group stratification technique as used in the present study, differentiating good and poor jumpers from a sample of collegiate basketball players. Greater rate of force development in a braking phase, differentiated from the unloading phase and demonstrating greater deconstruction of the downward phase than employed in the current study, and a shorter time to takeoff were key to good performance.…”

Optimization-based subject-specific planar human vertical jumping prediction: Model development and validation

“…GRFs within all jumping phases are related, as a better force application strategy with one or more phase can result in a greater jumping. [37][38][39][40] In this study we only compare the maximum GRFs during the weighting, unweighting, braking, and propulsion phases between the experiment and the simulation. Figure 4 shows that the difference between the experiment and the simulation in the maximum GRFs during the jump was in the range of 0.45%-2.23%.…”