Inspiratory muscle training for enhancing repeated-sprint ability: A pilot study

This pilot study examined the effect of inspiratory muscle training (IMT) on repeated-sprint ability and vastus lateralis reoxygenation. Ten recreationally trained subjects were randomly divided into two groups to complete 4 weeks of IMT or Sham (placebo) training. Pre- and post-intervention, a repeated-sprint ability (RSA) test was performed in both normoxia and hypoxia (FiO2 {approx} 14.5%). Vastus lateralis reoxygenation (VLreoxy), defined as peak to minimum amplitude deoxyhaemoglobin for each sprint/recovery cycle, was assessed during all trials using near-infrared spectroscopy. For total work performed, power analysis revealed that for small, medium and large effects (Cohens f), sample sizes of n = 8, 16 and 90 respectively, are required to achieve a power of 80% at an level of 0.05. Maximal inspiratory mouth pressure increased in IMT by 36.5%, 95% CI [20.9, 61.6] and by 2.7%, 95% CI [-4.46, 8.8] in Sham. No clear difference in the change of work completed during the sprints between groups were observed in normoxia (Sham -0.805 kJ, 95% CI [-3.92, 0.39]; IMT -2.06 kJ, 95% CI [-11.5, 4.96]; P = 0.802), or hypoxia (Sham -3.09 kJ, 95% CI [-7, 0.396]; IMT 0.354 kJ, 95% CI [-1.49, 2.1]; P = 0.802). VLreoxy in IMT increased by 9.34%, 95% CI [5.15, 13.7] in normoxia only. In conclusion, despite a large increase in IMT, this was only associated with a small effect on RSA in our pilot study cohort. Owing to a potentially relevant impact of training the inspiratory musculature, future studies should include a sample size of at least 16-20 to detect moderate to large effects on RSA.