Breathing technique-dependent acute cardiopulmonary responses during squats in healthy females.

Breath-holding (BH), including variations of the Valsalva maneuver, is used during resistance exercise to stabilize the trunk and increase intra-abdominal pressure. However, its hemodynamic and ventilatory effects during low-to-moderate intensity strength training in women remain unclear. In a randomized crossover design, 17 healthy, young females performed squats at three intensities (bodyweight, 25%, and 50% of 10-repetition maximum) under two breathing conditions: BH or controlled breathing (CB) during the concentric phase. Cardiopulmonary responses were assessed using impedance cardiography, spirometry, and auscultatory arterial blood pressure measurement. Across intensities, BH elicited significantly higher heart rate (+2%-5%; p < 0.01), cardiac output (+3%-8%; p = 0.02), systolic blood pressure (+16%-23%; p < 0.01), rate-pressure product (+20%-30%; p < 0.01), and rating of perceived exertion (+14%-19%; p < 0.01) than CB. Oxygen uptake (-11%-15%; p < 0.01) and minute ventilation (-16%-17%; p < 0.01) were significantly reduced during BH, followed by a post-exercise overshoot. Stroke volume and blood lactate did not differ significantly. Even at low-to-moderate intensities, BH during resistance exercise induces moderate cardiovascular strain and transient ventilation reductions. In healthy, young women, these responses remained within a non-critical range, suggesting that short, controlled BH may represent a viable and safe strategy during strength training.