Interactions between upper limb asymmetry, isokinetic shoulder function, and sprint performance in wheelchair rugby: a preliminary study

Wheelchair rugby (WR) athletes often present neuromuscular asymmetries due to the nature of their impairments and sport-specific demands. Understanding whether these asymmetries influence performance is important for characterizing functional profiles and guiding training strategies. Therefore, the aim of this study was to determine whether muscle asymmetry and balance influence the relationship between isokinetic muscle function variables and sprint performance in WR athletes.

Nine elite WR athletes underwent isokinetic testing of shoulder flexion, extension, abduction, and adduction at 180°/s to determine peak torque normalized by body weight (PT/BW), bilateral asymmetry based on PT/BW, and agonist/antagonist ratios. Sprint performance was assessed using a sprint test. Spearman correlations and univariate regression models evaluated associations between isokinetic variables, bilateral asymmetry (continuous variable representing the magnitude of the percentage difference in peak torque between the limbs), muscle balance (agonist and antagonist ratio), and mean sprint speed.

The magnitude of bilateral peak torque differences varied across athletes and shoulder movements. Shoulder adduction showing significantly greater asymmetry than abduction (p = 0.009). All athletes demonstrated marked agonist/antagonist imbalances. Shoulder extension PT/BW was significantly correlated with mean sprint speed (ρ = -0.813, p = 0.008), while flexion showed significance only within the flexion-extension balance model (β = -0.68, p = 0.049). No significant correlations with mean sprint speed were observed for shoulder abduction or adduction PT/BW, and neither bilateral asymmetry nor agonist/antagonist balance showed significant main effects or interactions with PT/BW in the regression models.

These findings suggest that, in WR athletes with cervical spinal cord injury, sprint performance may depend more on the available shoulder force-generating capacity than on the degree of bilateral symmetry or agonist/antagonist balance measured under controlled isokinetic conditions. From an applied perspective, strength and conditioning programs should prioritize functional torque production while interpreting asymmetries within each athlete's impairment-specific neuromuscular profile rather than treating symmetry restoration as a universal training target.