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Abstract

Inspiratory muscle exercise and slow breathing have been demonstrated to improve blood pressure control, possibly via an improved sympatho/vagal balance mechanism. Purpose: To test the hypothesis that inter-set inspiratory muscle exercise would attenuate the increase of sympatho/vagal activity ratio and the reduction of baroreflex sensitivity after high-intensity resistance exercise. Methods: A total of 14 recreational active males (n=8, aged= 24±1yrs, BMI=22±1 kg/m2) and females (n=6, aged=24±1yrs, BMI=22±2 kg/m2) were recruited and underwent maximum muscle strength (1RM), maximum inspiratory pressure (PImax) determination after familiarization. Participants were asked to engage in 4 acute bouts of high-intensity resistance exercise (bench press, bicep curl, and squat exercise at 80%1RMÍ10repsÍ5setsÍ1.5min rest interval) with no inter-set breathing control (CON), slow breathing (10 breaths/min, SB), 30%PImax, and 60%PImax by using a randomized, repeated measures study design. Blood pressure, brachial-ankle pulse wave velocity(baPWV), hemodynamic parameters, heart rate variability (HRV), and baroreflex sensitivity (BRS) were obtained at Pre, Post, and Post-30 and Post-60 minutes. Twenty-four-hour ambulatory blood pressure monitoring (24hr AMBP) was also performed following exercise to determine average real variability (ARV), the indicator of blood pressure variability. Female participants were tested during the early follicular phase to avoid possible confounding effects from the menstrual cycle. Results: Compared with the Pre, HR significantly increased at Post in all treatments and remained elevated at Post-30 min in CON (P=0.005) and 60%PImax (P=0.03). Cardiac output increased at Post in CON (P=0.05) and 60%PImax(P=0.04), whereas stroke volume and mean arterial pressure were maintained. There was no time and treatment difference in post-exercise blood pressure, 24-hour AMBP, and baPWV. Compared with the Pre, LF/HF ratio was significantly higher at Post in CON (P=0.001) and SB (P=0.03), whereas 30%PImax and 60%PImax did not elicit significant changes. BRS was significantly reduced at Post in CON (P=0.04), yet it was maintained and significantly higher (P=0.03) at Post-60 min after the 30%PImax session. There were no group differences on 24hrAMBP ARV, despite 30%PImax appeared to elicit lower variability on systolic blood pressure. Conclusions: Compared with no breathing control, inter-set inspiratory muscle activation with resistance at 30%PImax appears effective in maintaining autonomic regulation and baroreflex sensitivity when engaging in high-intensity resistance exercise in apparently healthy young adults.

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