Exercise-induced inspiratory muscle fatigue during swimming: the effect of race distance

Exercise-induced inspiratory muscle fatigue (IMF) has been quantified for several sports. However, it is not yet known if, or to what extent, IMF is determined by the competition distance. The aim of the present study was to assess the influence of 3 different competitive front-crawl swimming race distances on the magnitude of IMF. Ten well-trained swimmers from a local swim team participated in the study and on separate days completed maximal 100-, 200-, and 400-m time trials (TTs). Before and after each trial, maximal inspiratory pressure (MIP) was measured and %IMF determined from pre- and post-time-trial differences in MIP. The heart rate (HR) and rate of perceived dyspnea (RPD) was also assessed. For all distances, posttrial MIP was lower than pretrial MIP, though this was only significant for 100 m (p < 0.05). There were no differences between distances for absolute posttrial MIP. The %IMF after the 100-m TT (8.2 ± 4.1%) was, however, significantly greater than the 400 m (4.9 ± 3.8%) TT (p < 0.05) but not 200-m TT. There were no differences between trials for HR or RPD (p > 0.05). There were no relationships between %IMF and mean pretrial MIP (r = -0.28, p > 0.05) or between %IMF and time for any TT (100 m, r = 0.25; 200 m, r = 0.34; 400 m r = 0.18; p > 0.05). The lack of difference between trials for posttrial absolute MIP suggests that race distance during swimming does not substantially influence the degree of IMF.