Force-velocity profiling of elite wheelchair rugby players over multiple sprints.

Introduction:

Wheelchair sprinting is a key aspect of a WCR match and needs to be evaluated and understood accordingly. Because of the high velocities, there is little time for the upper-body muscles to contract, to couple the hand with the rotating rim-wheel interface and to transfer the power to the wheelchair. Thus, wheelchair sprinting is a challenging upper-body movement.

It is currently unknown how much sprint power output wheelchair rugby athletes can produce maximally and how we can optimize training methods and wheelchair design to be able to effectively use power output.

It is currently unknown whether the force–velocity relationship also exists in wheelchair sprinting in a diverse group of WCR athletes. The force–velocity relationship can be explored by applying increased rolling resistances on a wheelchair ergometer during a series of short sprints.

Study aim: To investigate the effect of increased rolling resistance on sprint power output, force production and velocity and to describe the underlying propulsion technique in elite WCR athletes.

Methods:

Thirteen wheelchair rugby (WCR) athletes completed five 15 s wheelchair sprints in their own rugby wheelchair on an instrumented dual-roller wheelchair ergometer. The first sprint was performed against a close to over ground resistance and in each of the following sprints, the resistance increased with 80% of that resistance (referred to as S100, S180, S260, S340, and S420).

A repeated-measures ANOVA examined differences between sprints. Subsequently, linear regression analyses examined the individual force–velocity relations and then, individual parabolic power output curves were modelled. 

Main findings:

• PO_mean, F_meanand total work significantly increased whilst v_mean and v_max significantly decreased from S100 to S420.
• Increased rolling resistance led to significantly lower velocities (−36%), higher propulsion forces (+150%) and higher power outputs (+83%).
• These differences were accompanied by a lower push frequency, higher push time, yet a constant recovery time and contact angle.
• The peak of the power output parabola (i.e., the optimal velocity) occurred on average at 3.1 ± 0.6 ms⁻¹.
• The increases in power output can be explained by longer push times (+62%) and similar contact angles that allowed for more time to couple the hand to the rim-wheel interface, to contract the upper-body musculature, and transfer forces to the wheelchair. 
• Individual force–velocity profiles can be used for training recommendations or technological changes to better exploit power generation capabilities of the WCR athletes' musculoskeletal system.
• Athletes with a steep force–velocity curve can produce much more power at an increased resistance and are clearly limited by a high hand speed. 

Reference:

Janssen RJF, de Groot S, Van der Woude LHV, Houdijk H, Goosey-Tolfrey VL, Vegter RJK. Force-velocity profiling of elite wheelchair rugby players by manipulating rolling resistance over multiple wheelchair sprints. Scand J Med Sci Sports. 2023 Aug;33(8):1531-1540. DOI: 10.1111/sms.14384. Epub 2023 May 14. PMID: 37183537.