Lower-limb amputees typically require some form of prosthetic limb to ride a bicycle for recreation or when competing. At elite-level racing speeds, aerodynamic drag can represent the majority of the resistance acting against a cyclists forward motion. As a result, the reduction of such resistance is beneficial to an amputee whereby the form and function of the prosthetic limb can be optimised through engineering. To measure the performance of such limbs, field testing provides a cost effective and context specific method of aerodynamic drag measurement. However, few methods have been formally validated and none have been applied to amputees with lower-limb amputations. In this paper, an elite level para-cyclist wore two different prosthetic limb designs and had their total aerodynamic drag of a wind tunnel reference method statistically correlated against a velodrome-based virtual elevation field test method. The calculated coefficient of variation was in the range of 0.7-0.9% for the wind tunnel method and 2-3% for the virtual elevation method. A 0.03m 2 difference was identified in the absolute values recorded between the two methods. Ultimately, both methods exhibited high levels of precision, yet relative results to each other. The virtual elevation method is proposed as a suitable technique to assess the aerodynamic drag of amputee para-cyclists.
Previous studies have proposed that an aerodynamically optimised prosthetic limb could provide performance enhancement for competitive paracyclists. Four different designs of prosthetic limbs were assessed for their impact upon the aerodynamic drag of an elite cyclist with a lower-limb amputation. The pylon area acted as the controlled location for the differences in design between the test prostheses. A validated field test method was used to derive the participant's total aerodynamic drag when using the prostheses designs. The field test method produced a repeatable experimental process and demonstrated that small changes in form made to the pylon region resulted in measurable differences to the participant's cycling performance. In addition, statistical significance was obtained between a baseline design and the prostheses prototype with the greatest aspect ratio (p=<0.05). The magnitude of improvements recorded in this study could potentially influence a rider's finishing time at international sporting events like the Paralympic Games. Implications for Rehabilitation • Small changes in form made to a cycling prostheses design can potentially deliver worthwhile performance enhancement. • Prosthetists may obtain greater end-user satisfaction by taking a broader approach to sports prostheses design than just fit and biomechanical function alone. • This study indicates that other regions of the cycling prosthesis could now benefit from aerodynamic optimisation with the aim to further improve paracycling performance.
Unexplored in scientific literature, Q Factor describes the horizontal width between bicycle pedals and determines where the foot is laterally positioned throughout the pedal stroke. The aim of the study was to determine whether changing Q Factor has a beneficial effect upon cycling efficiency and muscular activation. A total of 24 trained cyclists (11 men, 13 women; VO2max 57.5 ml·kg/min ± 6.1) pedaled at 60% of peak power output for 5 min at 90 rpm using Q Factors of 90, 120, 150, and 180 mm. Power output and gas were collected and muscular activity of the gastrocnemius medialis (GM), tibialis anterior (TA), vastus medialis (VM), and vastus lateralis (VL) measured using surface electromyography. There was a significant increase (P < 0.006) in gross mechanical efficiency (GME) for 90 and 120 mm (both 19.38%) compared with 150 and 180 mm (19.09% and 19.05%), representing an increase in external mechanical work performed of approximately 4-5 W (1.5-2.0%) at submaximal power outputs. There was no significant difference in the level of activity or timing of activation of the GM, TA, VM, and VL between Q Factors. Other muscles used in cycling, and possibly an improved application of force during the pedal stroke may play a role in the observed increase in GME with narrower Q Factors.
Correct bicycle fit is important, and kinematic instability must be addressed to reduce the risk of knee injury. A change in Q Factor (horizontal distance between crank arms) has been shown to decrease metabolic cost. The combined effect upon gross mechanical efficiency (GME) and knee variability is unclear, however; there is no known simple method to predict self-selected Q Factor (SSQ). The SSQ was hypothesized to provide the greatest GME and least variability at the knee. Ten trained cyclists completed bouts of submaximal cycling at a range of Q Factors. The effectiveness of hanging and stepping tasks as predictors of SSQ was also tested. Measured SSQ (142 mm) provided the best combination of GME and knee stability compared with other Q Factors, and could be accurately predicted using a simple hanging task. The SSQ has the potential to lower the risk of knee injury and provide increased efficiency whilst cycling.
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