INTRODUCTION: Inspiratory muscle fatigue (IMF) has been reported following 200 m front crawl (F/C) swimming in national and international standard masters` swimmers (Lomax & McConnell, 2003). Whether the magnitude of IMF varies between strokes and whether expiratory muscle fatigue (EMF) occurs in highly trained age-group swimmers was addressed in this study. METHODS: Following institutional ethical clearance, 11 national standard British age-group swimmers were recruited (mean ± SD: age 14 ± 1.4 years; body mass 55.9 ± 7 kg; stature 151.5 cm ± 5.1 cm) to undertake four ((1 x: F/C, back stroke (B/K), breast stroke (B/R) and butterfly (fly)) maximal 200 m swims from a push start. Each swim was undertaken on a separate occasion, at the same time of day, in the same swimming pool and followed a standardised 600 m warm-up. Inspiratory and expiratory mouth pressure (MIP and MEP, respectively; RPM Micro Medical, UK) were recorded pre and post each 200 m swim. In addition, breathing frequency (fr) and stroke count (SC) were recorded per swim. RESULTS: Two-way repeated measures ANOVA revealed similar MIP values (p = 0.590) between strokes pre- (F/C 110 ± 21 cmH2O; B/K 112 ± 18 cmH2O; B/R 112 ± 24 cmH2O; Fly 110 ± 17 cmH2O) and post- (F/C 88 ± 22 cmH2O; B/K 93 ± 23 cmH2O; B/R 86 ± 19 cmH2O; Fly 96 ± 23 cmH2O) swim, although MIP did decline (p < 0.001) following each 200 m swim. No differences were observed in MEP either pre- (F/C 99 ± 31 cmH2O; B/K 98 ± 31 cmH2O; B/R 95 ± 27 cmH2O; Fly 99 ± 31 cmH2O) or post- (F/C 100 ± 39 cmH2O; B/K 99 ± 35 cmH2O; B/R 96 ± 35 cmH2O; fly 90 ± 28 cmH2O) swim at any time point (p = 0.727) or between strokes (p = 0.744). No relationship (p > 0.05) was observed between fr and the percentage change in MIP (F/C r = -.456; B/K r = .218; B/R r = .218; Fly r = .312) or between SC and the percentage change in MIP (F/C r = .458; B/K r = .496; B/R r = .520; Fly r = -.161). DISCUSSION: IMF occurs in response to maximal 200 m swimming in each of the four strokes but EMF does not. Although the magnitude of IMF was not significantly different between strokes, there was a trend for IMF to be higher in F/C and B/R (~20-23%) compared to Fly and B/K (13-17%). Furthermore, the magnitude of fatigue was not related to breathing frequency and had no effect on stroke count.
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