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David S. Haydon, Ross A. Pinder, Paul N. Grimshaw and William S.P. Robertson

Purpose: Maximal acceleration from standstill has been identified as a key performance indicator in wheelchair rugby; however, the impact of classification and kinematic variables on performance has received limited attention. This study aimed to investigate kinematic variables during maximal acceleration, with level of activity limitation accounted for using sport-classification scores. Methods: Based on their sporting classification scores, which reflect combined trunk, arm, and hand function, 25 elite wheelchair rugby players were analyzed in high-, mid-, and low-point groups before completing five 5-m sprints from a stationary position. Inertial measurement units and video analysis were used to monitor key kinematic variables. Results: Significant differences in kinematic variables were evident across the classification groups, particularly for the first stroke-contact angle (1-way ANOVA F 2,122 = 51.5, P < .05) and first stroke time (F 2,124 = 18.3, P < .05). High-point players used a first stroke-contact angle that was closer to top dead center of the wheel than either other group, while also using a shorter overall stroke time than low-point players. A linear mixed-effects model was used to investigate how kinematic variables influenced performance, with results suggesting that increased release angles (ie, farther around the wheel) and decreased stroke angles resulted in larger peak accelerations. Further investigation revealed that these results are likely influenced by strong relationships for the high-point group, as there was often no clear trend evident for midpoint and low-point groups. Conclusion: Findings show that various propulsion approaches exist across classification groups, with this information potentially informing individual wheelchair setups and training programs.

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Amy R. Lewis, William S.P. Robertson, Elissa J. Phillips, Paul N. Grimshaw and Marc Portus

For the wheelchair racing population, it is uncertain whether musculoskeletal models using the maximum isometric force-generating capacity of nonathletic, able-bodied individuals are appropriate, as few anthropometric parameters for wheelchair athletes are reported in the literature. In this study, a sensitivity analysis was performed in OpenSim, whereby the maximum isometric force-generating capacity of muscles was adjusted in 25% increments to literature-defined values between scaling factors of 0.25x and 4.0x for 2 elite athletes, at 3 speeds representative of race conditions. Convergence of the solution was used to assess the results. Artificially weakening a model presented unrealistic values, while artificially strengthening a model excessively (4.0x) demonstrated physiologically invalid muscle force values. The ideal scaling factors were 1.5x and 1.75x for each of the athletes, respectively, as was assessed through convergence of the solution. This was similar to the relative difference in limb masses between dual-energy X-Ray absorptiometry data and anthropometric data in the literature (1.49x and 1.70x), suggesting that dual-energy X-ray absorptiometry may be used to estimate the required scaling factors. The reliability of simulations for elite wheelchair racing athletes can be improved by appropriately increasing the maximum isometric force-generating capacity of muscles.