The impact of full stroke versus legs only maximal effort swimming and different breathing pattern on respiratory muscle fatigue.

Background: This study investigated the impact of different breathing patterns and stroke variations on inspiratory and expiratory muscle fatigue (IMF and EMF) in front crawl swimming.

Methods: Twelve club-level swimmers (3 females) performed four maximal effort 200-m front crawl swims in a random order: breathing every two strokes (B2), every four strokes (B4), ad libitum via a snorkel (S), and legs only with a kickboard (K).

Results: Postswim maximal inspiratory mouth pressure decreased in B2 (34±26%), B4 (41±23%), S (26±16%), and K (13±15%). The only significant difference in IMF was between B4 and K. Significant EMF was observed only in S (12±11%) and K (13±15%). IMF was greater than EMF in B2 and B4. Swim time was slower in K (217 (199-231) s) compared to B2 (139 (136-156) s), B4 (142 (138-155) s), and S (142 (138-155) s), but similar among B2, B4, and S. Postswim, pH and HCO3^- levels decreased, while blood lactate levels increased in all trials. Full stroke and legs-only front crawl swimming caused IMF, regardless of breathing restrictions. However, IMF was lower when breathing was unrestricted, and the upper body was immobilized compared to full stroke and highly restricted breathing. EMF was not observed when breathing was restricted and tended to be lower than IMF.

Conclusions: These findings suggest that the mechanisms of IMF and EMF differ during front crawl swimming.