Effects of Sprint-Interval and Endurance Respiratory Muscle Training Regimens

INTRODUCTIONRecently a novel, time-saving respiratory muscle sprint-interval training (RMSIT) was developed. To test the extent to which RMSIT improves respiratory muscle performance compared with a conventional respiratory muscle endurance training (RMET), a novel incremental respiratory muscle test (IncRMT), loading inspiratory and expiratory muscles, was designed to assess performance changes associated with respiratory muscle training (RMT). METHODSHealthy, moderately trained males and females (age26 ± 5 yr, V˙O2peak47 ± 12 mL·min·kg) were randomized and balanced to three groups (RMSIT 5m/5f; RMET 6m/6f; PLAT 5m/6f). Lung function, respiratory muscle strength, and IncRMT performance were tested before and after 1 month of RMT. During the IncRMT, muscle activity and muscle deoxygenation were assessed via surface EMG and near-infrared spectroscopy of sternocleidomastoid (STERNO), intercostal (INTER), and abdominal (ABDO) muscles. RESULTSTwo-way ANOVA revealed a main effect of training for increased maximal voluntary ventilation (P = 0.001) and maximal inspiratory pressure (P = 0.017). Both RMT groups increased work of breathing during training sessions to the same extent (RMSIT+17.4 ± 8.9 kJ; RMET+26.2 ± 16.1 kJ; P = 0.143) with a larger increase in average mouth pressure in RMSIT (RMSIT+20.0 ± 15.0 cm H2O; RMET+3.3 ± 1.5 cm H2O; P = 0.001). After training, IncRMT duration increased in both RMT groups compared with PLAT (RMSIT+5.6 ± 2.1 min, P = 0.0006 vs PLAT; RMET+3.8 ± 4.2 min, P = 0.020 vs PLAT). At similar work, only INTER activity during inspiration increased after RMET. Higher performance after RMSIT was associated with higher activity in STERNO and ABDO, but after RMET, STERNO, INTER, and ABDO showed higher activity. CONCLUSIONOne month of RMSIT and RMET shows similar improvements in respiratory muscle performance despite different duration of training sessions. Also, muscular adaptations might differ.