LAUSR

Purpose There is little evidence of the ergogenic effect of flow-resistive masks worn during exercise. We compared a flow-resistive face mask (MASK) worn during high-intensity interval training (HIIT) against pressure threshold loading inspiratory muscle training (IMT). Methods 23 participants (13 males) completed a 5 km time trial and six weeks of HIIT (3 sessions weekly). HIIT ( n  = 8) consisted of repeated work (2 min) at the speed equivalent to 95% $${\dot{\text{V}}}$$ V ˙ O 2 peak with equal rest. Repetitions were incremental (six in weeks 1, 2 and 6, eight in weeks 3 and 4 and ten in week 5). Participants were allocated to one of three training groups. MASK ( n  = 8) wore a flow-resistive mask during all sessions. The IMT group ( n  = 8) completed 2 × 30 breaths daily at 50% maximum inspiratory pressure ( P Imax ). A control group (CON, n  = 7) completed HIIT only. Following HIIT, participants completed two 5 km time trials, the first matched identically to pre-intervention trial (ISO time), and a self-paced effort. Results Time trial performance was improved in all groups (MASK 3.1 ± 1.7%, IMT, 5.7 ± 1.5% and CON 2.6 ± 1.0%, p  < 0.05). IMT improved greater than MASK and CON ( p  = 0.004). Post intervention, P Imax and diaphragm thickness were improved in IMT only (32% and 9.5%, respectively, p  = 0.003 and 0.024). Conclusion A flow-resistive mask worn during HIIT provides no benefit to 5 km performance when compared to HIIT only. Supplementing HIIT with IMT improves respiratory muscle strength, morphology and performance greater than HIIT alone.