Author(s): AMINIAGHDAM, S., WÖRGÖTTER, S., SCHARBERT, J., BÖHMER, M., BAUMERT, P., FINK, C., Institution: UMIT TIROL– PRIVATE UNIVERSITY FOR HEALTH SCIENCES AND HEALTH TECHNOLOGY, Country: AUSTRIA, Abstract-ID: 2164

INTRODUCTION:
Along the standardization–ecological-validity continuum, hands-on-hips single-leg countermovement jumps (SL-CMJ) provide repeatable stretch–shortening cycle (SSC) benchmarks but are self-paced and context-poor. Semi-immersive extended reality (XR) can add ball-coupled, externally timed goals (e.g., heading) while retaining laboratory-grade kinetics, potentially revealing soccer-relevant jump–landing strategies (1). We compared XR jump–head–land (XR-JHL) with SL-CMJ and tested moderation by sex and limb dominance.
METHODS:
Forty-five competitive amateur soccer players (22 males, 23 females; dominance = preferred kicking leg) performed bilateral SL-CMJ and XR-JHL using a semi-immersive XR system (MotumXR). In XR-JHL, athletes used arms freely, timed the jump to head a time-standardized, height-scaled virtual ball at a prescribed contact height, and landed on the same force plate. 3D kinematics (Qualisys; 200 Hz) and ground reaction forces (AMTI; 1000 Hz) were synchronized with MotumXR and displayed on a wall screen (4.85×2.75 m; viewing distance 5.33 m). Valid trials required ball contact, clean force-plate contact, and a stable single-leg landing. Outcomes were jump height, RSI, and discrete sagittal-plane peak trunk/lower-limb kinematics and kinetics (moments, power). Mixed ANOVA tested Condition (XR-JHL vs SL-CMJ) with Sex and Dominance (α=0.05).
RESULTS:
Compared with SL-CMJ, XR-JHL increased jump performance (height +4.0–6.4 cm; Sex×Condition×Dominance p=.018; RSI +13%, p<.01). XR-JHL induced a more extended jump strategy (lower trunk/hip/knee flexion; ankle dorsiflexion −2°) with higher loading (knee moment +0.33; ankle moment +0.48–0.61; all p≤.007) and a distal shift in positive power (knee +1.41; ankle +2.41 W·kg⁻¹) with lower hip positive power (−0.61 W·kg⁻¹). Dominance effects were present (Dom < NonDom for ankle dorsiflexion, knee moment, and positive knee/ankle power; all p<.01) and XR amplified limb-specific loading (Condition×Dominance for ankle moment; p≤.007). During landing, XR-JHL was more upright with sex/limb moderation, with lower knee moment (−0.12; p<.05) but higher ankle moment (+0.56; p<.01), plus reduced ankle negative power (−8.1 to −9.6 W·kg⁻¹), especially in males.
CONCLUSION:
Externally timed, ball-coupled XR heading reshaped SSC expression versus SL-CMJ: athletes jumped higher and more reactively, yet adopted a more extended strategy with distally redistributed peak demands toward the knee–ankle complex. Kicking-leg dominance systematically moderated these signatures (dominant limbs: lower dorsiflexion and reduced knee/ankle positive power), and XR magnified limb-specific loading, exposing soccer-relevant asymmetries that self-paced benchmarks may mask. Joint power complemented moments by distinguishing high-moment/low-velocity (“stiffer”) distal landing control under soccer-specific constraints from higher-excursion solutions typical of SL-CMJ.
REFERENCES:
1) Pinder et al., J Sport Exerc Psychol, 2011