Inspiratory muscle training improves the swimming performance of competitive young male sprint swimmers

Inspiratory muscle training (IMT) stimulates the strengthening of the respiratory muscles by placing a resistance to the entry of air into the lung. The objective was to observe the effect of IMT on swimming performance, and its relationship with inspiratory strength and lung function.Fifteen male swimmers (age=15.1±1.1 years) were divided into an experimental group (EG; N.=9) and a sham control group (SCG; N.=6). Lung flows/volumes using spirometry, dynamic inspiratory strength (S-Index), maximum inspiratory flow (MIF), and swimming tests (50-m, 100-m and 200-m) were measured before and after a four-week aerobic swimming training program (R1-R2) and IMT. An initial load at 50% and 15% of S-Index was adjusted for EG and SCG respectively. Only the EG increased the initial load by 5% each week.The S-Index and MIF were only increased in the EG after IMT (∆S-Index=18.0±8.8 cmH2O and ∆MIF=0.7±0.33 L·min-1; P<0.05). The same occurred for FVC (∆=0.3±0.2 l), and MVV (∆=6.9±3.6 l·min-1) (P<0.05). For swimming performances, the EG swimming times decreased significantly respect to CG for 50-m (∆EG=-1.2±0.3 s vs. ∆CG=-0.1±0.2 s), 100-m (∆EG=-2.9±1 s vs. ∆CG=-0.7±0.5 s) and 200-m (∆EG=-7.3±2.8 s vs. ∆CG=-2.0±1 s) with P<0.05. Finally, the S-Index and MIF had a negative correlation with swimming performances for 50-m (S-Index, r=-0.72; MIF, r=-0.70) and 100-m (S-Index, r=-0.65; MIF, r=-0.62) with P<0.05.A short-period IMT increases the maximum S-Index, ventilation and MIF which positively influence the swimming performance of young swimmers.