Locomotor-respiratory coupling in wheelchair racing athletes: a pilot study

Purpose: In wheelchair racing, respiratory muscles of the rib cage are concomitantly involved in non-ventilatory functions during wheelchair propulsion. However, the relationship between locomotor-respiratory coupling (LRC: the ratio between push and breathing frequency), respiratory parameters and work efficiency is unknown. Therefore, the aim of the present study was to investigate the LRC in wheelchair racers over different race distances. Methods: Eight trained and experienced wheelchair racers completed three time-trials over the distances of 400m, 800m and 5000m on a training roller in randomized order. During the time trials, ventilatory and gas exchange variables as well as push frequency were continu-ously registered to determine possible LRC strategies. Results: Four different coupling ratios were identified, namely 1:1; 2:1, 3:1 as well as a 1:1/2:1 alternating type, respectively. The 2:1 coupling was the most dominant type. The 1:1/2:1 alternating coupling type was found predominantly during the 400m time-trial. Longer race distances tended to result in an in-creased coupling ratio (e.g., from 1:1 towards 2:1), and an increase in coupling ratio towards a more efficient respiration was found over the 5000m distance. A significant correlation (r=0.80, p<0.05) between respiratory frequency and the respiratory equivalent for oxygen was found for the 400m and the 800m time-trials. Conclusions: These findings suggest that a higher coupling ratio indicates enhanced breathing work efficiency with a concomitant deeper and slower respiration during wheelchair racing. Thus, the selection of an appropriate LRC strategy may help to optimize wheelchair racing performance.