Energy cost of pushing a wheelchair on various gradients in young men

This study investigated the effects of pushing a wheelchair on the energy cost of walking (C_w; defined as the ratio of the steady-state oxygen consumption to the walking speed) and economical speed (ES) on the level and ±5% gradients. Eight pairs were formed from twelve young men to minimize variation in body weight between pushing and assisted participants. The State Trait Anxiety Inventory (STAI) test was conducted to evaluate wheelchair occupants' anxiety before and after each trial. The C_w values were significantly higher when pushing a wheelchair on the uphill gradient at more than 45m/min. ES was significantly lower when pushing a wheelchair on the level (-8.5%) and uphill gradient (-9.1%), but not on the downhill gradient (-0.3%). Individual ES was also estimated using the concept of "Froude number", and "estimated" ES was significantly correlated with "measured" ES even when pushing a wheelchair on the downhill gradient. The STAI score was not significantly increased except at 105m/min, regardless of gradient. These results indicated that the fastest walking speed without an enhancement in wheelchair occupants' anxiety corresponds to ES when pushing a wheelchair with a seated occupant on all gradients, at least in young fit men. Relevance to industry: This study provides information on alterations in ES while pushing a wheelchair on different gradients, with the associated perspective of wheelchair occupants' anxiety. The results are useful for reducing energy expenditure and/or avoiding the early onset of fatigue in wheelchair assistants without increasing wheelchair occupants' anxiety.