Effects of arm frequency during synchronous and asynchronous wheelchair propulsion on efficiency

To further understand the possible underlying mechanisms of the low efficiencies in hand rim wheelchair propulsion, this study examined efficiency indices at different arm frequencies during two propulsion modes (synchronous and asynchronous). Fourteen male able-bodied participants performed VO2PEAK tests for both propulsion modes. Subsequently two sub-maximal exercise tests examining synchronous and asynchronous propulsion were completed at an individualised velocity (60% of VO2PEAK). The freely chosen arm frequency (FCF), followed by four counter-balanced trials at 60, 80, 120, and 140% of FCF were performed. Gross, net, and work efficiency were determined. Gross efficiency was significantly lower (p<0.05) at arm frequencies >100%, and participants were more efficient between 60 to 100% FCF. These arm frequencies corresponded to 76+/-22 to 126+/-36 and 70+/-18 to 116+/-30 pushes x min(-1) (synchronous and asynchronous respectively). Trends in VO2, gross and work efficiency suggest that 80% of FCF produced the best economy and efficiency during both propulsion modes (non-significant). Gross and work efficiency at 80% FCF were 6.8+/-0.7% and 13.0+/-4.6% for synchronous and 7.0+/-0.8% and 11.5+/-1.6% for asynchronous respectively. The results suggest that during both modes of propulsion the FCF is not necessarily the most efficient.