Inspiratory resistive breathing during exercise in hypoxia increased muscle sympathetic nerve activity (55.7 vs 39.2 bursts/min) and mean blood pressure (134.3 vs 123.6 mmHg) compared to normoxia.
Absolute Event Rate: 55.7% vs 39.2%
The purpose of the present study was to clarify the influence of inspiratory resistive breathing during exercise under hypoxic conditions on muscle sympathetic nerve activity (MSNA) and blood pressure (BP). Six healthy males completed this study. The subjects performed a submaximal exercise test using a cycle ergometer in a semirecumbent position under normoxic inspired oxygen fraction (FiO2) = 0.21 and hypoxic (FiO2 = 0.12-0.13) conditions. The subjects carried out two 10-min exercises at 40% peak oxygen uptake spontaneous breathing for 5 min and voluntary breathing with inspiratory resistance for 5 min (breathing frequency: 60 breaths/min, inspiratory and expiratory times were set at 0.5 s each). MSNA was recorded via microneurography of the right median nerve at the elbow. A progressive increase in MSNA burst frequency (BF) during leg-cycling exercise with inspiratory resistance in normoxia and hypoxia were accompanied by an augmentation of BP. The increased MSNA BF and mean arterial BP (MBP) during exercise with inspiratory resistive breathing in hypoxia (MSNA BF, 55.7 ± 1.4 bursts/min, MBP, 134.3 ± 6.6 mmHg) were higher than those in normoxia (MSNA BF, 39.2 ± 1.8 bursts/min, MBP, 123.6 ± 4.5 mmHg). These results suggest that an enhancement of inspiratory muscle activity under hypoxic condition leads to large increases in muscle sympathetic vasomotor outflow and BP during dynamic leg exercise.
Katayama et al. (Thu,) conducted a other in Healthy (n=6). Exercise with inspiratory resistive breathing under hypoxic conditions vs. Exercise with inspiratory resistive breathing under normoxic conditions (FiO2 = 0.21) was evaluated on Muscle sympathetic nerve activity burst frequency (bursts/min). Inspiratory resistive breathing during exercise in hypoxia increased muscle sympathetic nerve activity (55.7 vs 39.2 bursts/min) and mean blood pressure (134.3 vs 123.6 mmHg) compared to normoxia.