The assessment of single-leg drop jump landing performance by means of ground reaction forces: A methodological study

Abstract

Background: Time to stabilization (TTS) and dynamic postural stability index (DPSI) are outcome measures based on ground reaction force (GRF) that are often used to quantify dynamic postural stability performance following a drop jump landing. However, their interrelations, as well as the overlap with other dynamic measures and static single-leg postural sway, are unknown. Research question: What is the relation among TTS and DPSI, how are they related to impact forces and dynamic postural sway, and how are all these dynamic measures related to static postural sway? Methods: A sample of 190 elite soccer players performed four single-leg drop jump landings. TTS in three directions (vertical, anteroposterior, and mediolateral), and DPSI were intercorrelated (Pearson's r), and related to impact forces and the magnitude of horizontal GRF (HGRF) from 0.4 to 2.4 s and 3.0-5.0 s following landing. All these measures were also correlated to HGRF in the static phase (i.e., 5.3-11.7 s). Results: The TTS measures were significantly interrelated (r = 0.28-0.53), but were not significantly correlated to DPSI. TTS was more strongly related to HGRF0.4-2.4 s (r = 0.54-0.75) than to HGRF3.0-5.0 s (r = 0.32-0.54) or impact forces (r=-0.28-0.36). Vertical TTS was not significantly related to impact forces. The DPSI was most strongly related to the vertical peak force (r = 0.85), and was not significantly related to HGRF of the dynamic periods. Furthermore, TTS and dynamic HGRF were significantly related to static HGRF (r = 0.34-0.80), while DPSI and impact forces were not. Significance: TTS and DPSI do not represent similar aspects of single-leg jump landing performance. The ability to stabilize posture seems to be represented by TTS and dynamic postural sway, which partly overlaps with static postural sway. In contrast, DPSI and vertical peak force mainly reflect the kinetic energy absorption during impact. The findings can help to better understand the meaning of the outcome measures, and to translate results to rehabilitation or prevention programs.

Postural Stability in Single-Leg Quiet Stance in Highly Trained Athletes: Sex and Sport Differences

“…Single-leg body sway parameters can be used for analyzing the static performance of stabilization in the condition of unilateral distribution of body weight, which is usual in sports activities. Good single-leg stabilization characteristic reflects on the smaller increase in vertical force and the shorter weight transfer in different movement tasks [17,18]. The single-leg stance test is also recommended for clinicians as a useful tool for a brief assessment of the risk of falling [19].…”

Validity of the frame subtraction method in dynamic postural stability

“…First, the DPSI did not correlate with the sum of the frame subtraction scores in any plane. The DPSI reflects the COM deceleration immediately after the jump landing, which indicates kinematic energy absorption [ 15 ]. In this study, the peaks of the frame subtraction scores were indicated immediately after single-leg jump landing.…”

“…The DPSI is indicated by the ground reaction force (GRF) that combines its components, such as the medial‒lateral stability index (MLSI), anterior‒posterior stability index (APSI), and vertical stability index (VSI). Since the DPSI is calculated by integrating the GRF components in three directions, it could comprehensively represent the ability to absorb the GRF in jump landing [ 15 ]. The DPSI is therefore a highly reliable and precise measure of dynamic postural stability [ 8 ].…”

Reliability of a novel dynamic test of postural stability in high-level soccer players

“…More importantly, outcome measures based on these forces, cannot be calculated. Parameters calculated from horizontal forces, such as TTS and absolute average forces, could provide relevant information on postural stability [ 47 , 48 ]. Another limitation of this study was the limited sample size (n = 42), although this was larger than in a recent study assessing reliability of drop landing [ 44 ].…”