Force– and power–time curve comparison during jumping between strength‐matched male and female basketball players

Abstract

The purpose of this study was to compare force- and power-time curve variables during jumping between Division I strength-matched male and female basketball athletes. Males (n = 8) and females (n = 8) were strength matched by testing a one-repetition maximum (1RM) back squat. 1RM back squat values were normalised to body mass in order to demonstrate that strength differences were a function of body mass alone. Subjects performed three countermovement jumps (CMJ) at maximal effort. Absolute and relative force- and power-time curve variables from the CMJs were analysed between males and females. Average force- and power-time curves were generated for all subjects. Jump height was significantly greater (p ≤ .05) in males than females. Absolute force was higher in males during the concentric phase, but not significantly different (p ≥ .05) when normalised to body mass. Significance was found in absolute concentric impulse between sexes, but not when analysed relative to body mass. Rate of force development, rate of power development, relative peak force, and work were not significantly different between sexes. Males had significantly greater impulse during the eccentric phase as well as peak power (PP) during the concentric phase of the CMJ than did females in both absolute and relative terms. It is concluded that sex differences are not a determining factor in measured force during a CMJ when normalised to body mass between strength-matched subjects. However, eccentric phase impulse and concentric phase PP appear to be influenced by sex differences independent of matching strength levels.

Understanding the Key Phases of the Countermovement Jump Force-Time Curve

“…The most important consideration here is that a consistent approach to BW determination is applied to enable fairer data comparisons between trials, sessions and athletes. The reason for the suggested weighing duration of 1 second is largely a consequence of a study conducted by Street et al (28) which showed that weighing durations of ≥ 1 second leads to a ≤ 1% overestimation of JH (calculated based on the impulse-momentum relationship) when compared to the maximum weighing duration of 2 seconds (29). A ≤ 1% overestimation of JH is considered acceptable (22,28), thus we recommend that the weighing phase should last for ≥ 1 second.…”

“…The reason for the suggested weighing duration of 1 second is largely a consequence of a study conducted by Street et al (28) which showed that weighing durations of ≥ 1 second leads to a ≤ 1% overestimation of JH (calculated based on the impulse-momentum relationship) when compared to the maximum weighing duration of 2 seconds (29). A ≤ 1% overestimation of JH is considered acceptable (22,28), thus we recommend that the weighing phase should last for ≥ 1 second. It is essential, however, that the athlete remains stood upright and as still as possible during the weighing phase as it is vital that center of mass (COM) velocity and displacement equal zero at the onset of movement for the numerical integration method to be accurate (29).…”

“…those which include strain gauges versus piezoelectric sensors) then we refer them to an excellent applied article by Beckham et al (2). An important point to note is that researchers and practitioners should attempt to establish sources of error associated with whichever force platform they use, in line with previous investigations (28,29). It might be that some force platforms demonstrate a poor ability to register rapid changes in force (1), for example, and so the data may need to be treated, in the form of digital filtering, before being analyzed.…”

“…It is essential, however, that the athlete remains stood upright and as still as possible during the weighing phase as it is vital that center of mass (COM) velocity and displacement equal zero at the onset of movement for the numerical integration method to be accurate (29). Street et al (28) showed that, when subjects were stood still, integrating the force-time data using the trapezoid rule (i.e. commencing forward dynamics procedures) anywhere from 0-1.5 seconds (the time range tested) before the onset of movement had no meaningful effect on JH.…”

“…To achieve this, the different CMJ phases must be identified using robust methodologies; this has not always been the case in the research literature and so warrants discussion with a view to its practical application (24,25). This may be because the identification of some CMJ phases requires the derivation of other variables from force-time data, or due to the many different terms used across studies to describe the different CMJ phases (5,10,11,(18)(19)(20)(21)(27)(28)(29).…”