Effect Of Inspiratory Muscle Training On Respiratory Muscle Metaboreflex During Resistive Breathing: Influence Of Sex

Mean arterial pressure (MAP) during inspiratory pressure threshold loading (IPTL) is greater in young adult males compared to females. Pressure threshold inspiratory muscle training (PT-IMT) attenuates MAP during IPTL in males, and this reduction persists after 5 wk of detraining (DT). Given that males have a greater MAP during IPTL than females, they may show a larger training response to PT-IMT. PURPOSE: To determine whether PT-IMT attenuates MAP during IPTL to a greater degree in males than females and remains low after DT. METHODS: Healthy participants (4 M, 5F; 25 ± 3 y) were instrumented with balloon catheters to measure esophageal, gastric, and transdiaphragmatic pressures. Participants performed IPTL (60% maximal inspiratory pressure (MIP), 0.7 inspiratory duty cycle, 15 breaths/min) until volitional exhaustion while beat-by-beat blood pressure and heart rate (HR) were measured. Participants performed PT-IMT (2 sets of 30 breaths at 50% MIP) 5 times/wk for 5 wk. MIP was assessed on a weekly basis to adjust training load. After 5 wk of PT-IMT and 5 wk of DT, participants repeated the baseline measurements. RESULTS: PT-IMT adherence was 95% (range = 86-100%) and MIP significantly increased (F = +16cmH2O, M = +27cmH2O, p < 0.05), and remained elevated after DT (F = +8cmH2O, M = +22cmH2O, p < 0.05). Pulmonary function, HR, and pressure-time product of respiratory pressures during IPTL were unaltered by PT-IMT (p > 0.05). Time-to-exhaustion (TTE) during IPTL increased from pre-to post-training (F = +27.8 min, M = +18.0 min, p < 0.05) and remained elevated after DT (F = +13.7 min, M = +10.2 min, p < 0.05). Using a linear mixed-effects model, the MAP during IPTL at the highest iso-time was significantly reduced post training (F = -5.1 mmHg, M = -12.2 mmHg, p < 0.05) and DT (F = -2.7 mmHg, M = -9.6 mmHg, p < 0.05). Males showed a larger attenuation of the MAP slope to IPTL after PT-IMT (-11.7 mmHg/%TTE, p < 0.05) compared to females (-5.4 mmHg/%TTE, p < 0.05). After DT, MAP during IPTL in males rose (+2.2 mmHg/%TTE, p < 0.05), whereas females maintained their MAP response (+1.1 mmHg/%TTE, p > 0.05) compared to post training. CONCLUSION: These findings demonstrate that females and males reduce their MAP during IPTL after PT-IMT. However, the inherent attenuation of MAP to IPTL in females lessens their adaptation to PT-IMT compared to males. Supported by: Natural Sciences and Engineering Research Council of Canada