Inspiratory muscle fatigue is a weakness or exhaustion of the inspiratory muscles, resulting in impaired sports performance. It is often observed after short duration (6 minutes), high intensity rowing and after stimulated cycling time-trials of 20 to 40 kilometres. To improve inspiratory muscle capacity and reduce inspiratory muscular fatigue, athletes are encouraged to engage in inspiratory muscle exercises that will increase the amount of lung capacity used.
Inspiratory muscle fatigue was investigated by Lomax and McConnell (2003) who discovered that high intensity swimming exercise can induce a statistically significant reduction in inspiratory muscle strength in as little as 2.7 minutes, the shortest duration of fatiguing exercise currently reported in the literature. In their study, Lomax and McConnell (2003), evaluated the inspiratory muscle strength of seven competitive 200 metre freestyle swimmers, performing at a race pace of 90 to 95 percent capacity. Inspiratory muscle strength was measured at residual volume (air remaining in the lungs after maximal expiration) using a hand held mouth pressure metre that measured maximal inspiratory pressure in the upright and supine positions. At maximal inspiratory pressure it was discovered that the aquatic environment appeared to accelerate the development and augment the magnitude of inspiratory muscle fatigue. It is suggested that work output of the inspiratory muscles must increase to rectify the chest deformation induced by immersion. Hence, this is perhaps why, a supine position in the water has the potential to exacerbate fatigue. However, this is not the case for all strokes, as the chest is not submerged during backstroke, and thus, allows the swimmer to adopt a more natural breathing pattern because their face is not immersed.
Lomax, M.E & McConnell, A.K. 2003. Inspiratory muscle fatigue in swimmers after a single 200 metre swim. Journal of Sports Sciences, 21, 659-664.