Effect of push frequency and strategy variations on economy and perceived exertion during wheelchair propulsion

Wheelchair locomotion is a cyclical activity and participants are free to select any push frequency–propulsion strategy combination that suits their needs at a given power output. The aim of the study was to examine the physiological effects of varying push frequency and strategy on pushing economy. Twelve male, able-bodied participants completed four, randomly assigned, 5-min bouts of submaximal exercise at 32 W on a wheelchair ergometer. Each bout of exercise combined two different push frequencies (40 and 70 push min⁻¹), with one of two different push strategies [synchronous (SYN): both arms pushing together, and asynchronous: one arm applying force to the wheel at a time). Physiological measures included oxygen uptake (V̇O₂), heart rate (HR) and blood lactate [La]_b concentration. Differentiated ratings of perceived exertion (RPE) were also recorded (overall, local and central). Separate ANOVA were used for V̇O₂, HR, [La]_b and RPE as the dependent variables. Where significant differences were identified, a Bonferroni post hoc test was used. The main effect for push frequency by strategy was significant for V̇O₂ (P<0.01). Scrutiny of the HR values showed that the SYN 40 condition was significantly less stressful than all other frequency–strategy combinations (P<0.01). RPE data supported these findings although they were found to be non-significant. When looking at [La]_b, both of the main effects were also significant showing the concentration was lower on average when the push rate was 40 as opposed to 70 (1.65 vs 2.14 mmol l⁻¹; P<0.01). This study provides further evidence that a low push frequency provides the most economical form of wheelchair propulsion especially when combined with a SYN strategy.