Respiratory muscle training improves thoracoabdominal coordination and work efficiency during incremental exercise in healthy subjects

Respiratory muscle training (RMT) by means of eucapnic hyperpnoea (Spirotiger®, Zurich, CH) is reported to increase exercise endurance but information on the effect of RMT on respiratory pattern and work efficiency during incremental exercise is lacking. Aim: to test the effect of RMT with Spirotiger on ventilatory pattern and aerobic function during incremental exercise in healthy subjects. Methods: 6 males collegiate athletes (age 20-24 years) involved in different disciplines such as soccer (2), rowing (1), triathlon (1), road skating (2) were recruited to partecipate in the study. A cardiopulmonary incremental test on a treadmill using a Balke protocol was performed by each subject before and after the RMT. VO2max, anaerobic threshold (AT) and the ΔVO2/ΔWR were determined. During the test ventilation and breathing pattern were evaluated by means of a portable inductive plethysmography (Lifeshirt, Vivometric, CA) and an index of thoracoabdominal coordination (the phase angle, Θ°) was calculated. RMT consisted of bouts of 20 min/day, 5 times/week, at Tidal Volume (Vt) = 60% of Vital Capacity (VC), respiratory frequency (ƒ) from 28 (first week) to 36. The remaining training schedule was unchanged. Results: after 4 weeks of RMT no changes were observed in VE, Vt, ƒ,VO2max, AT; Θ° at submaximal and maximal exercise significantly decreased from 24.2 (1.3) to 9.6 (0.5) p <0.001; ΔVO2/ΔW ml O2/W/min significantly decreased from 10.52 (.002) to 9.12 (.009), p =0.04. We conclude that 4 weeks RMT significantly improves thoracoabdominal coordination and work efficiency in healthy subjects during incremental exercise test.