# Comparison of Jump-Landing Biomechanics during and after Fatigue: Investigation on the Optimal Timing of Screenings under Fatigue

## TL;DR

This study examines how volleyball players' jump-landing movements change during and after fatigue, offering guidance on when to conduct injury risk assessments.

## Contribution

The study introduces a decision tree to guide optimal timing for biomechanical screenings during or after fatigue.

## Key findings

- Fatigue significantly alters pelvis-trunk and lower limb joint angles during spike jump-landings.
- Kinematic changes are more pronounced during fatigue compared to after fatigue.
- A decision tree is proposed to inform screening timing based on biomechanical alterations.

## Abstract

Fatigue has been considered a risk factor for sports injuries, modulating full-body jump-landing biomechanics. Biomechanical assessments of jump-landing manoeuvres are typically performed before and after short-term fatigue protocols, but changes during the protocol are often neglected. Therefore, this study investigated spike jump-landing strategy alterations during and following a short-term fatigue protocol in volleyball. Forty-three healthy, adult, male volleyball players participated in this study. Three-dimensional full-body kinematics were collected when performing spike jump-landings before, during and after a short-term fatigue protocol specific for volleyball. Full-body sagittal plane joint angles were calculated and analysed with curve analysis using one-way repeated measures ANOVA and post-hoc paired sample t-tests to investigate fatigue effects (p < 0.05). A significant main effect of fatigue was found for all kinematic variables (p = 0.015−0.041). More specifically, more pelvis-trunk flexion and less hip, knee, and ankle (dorsi-) flexion were observed during and after the protocol compared to baseline (p = 0.001−0.003). Moreover, less hip and knee flexion was observed during the protocol compared to after fatigue (p = 0.001−0.005). In conclusion, significant kinematic changes were found with fatigue, and these were somehow more pronounced during fatigue, possibly due to decreased attention towards the jump-landing task execution. A decision tree was provided to help researchers, coaches and/or clinicians in determining whether screenings should be better performed during or after fatigue, based on practical considerations.