Daily respiratory training with large intrathoracic pressures, but not large lung volumes, lowers blood pressure in normotensive adults

• Respiratory training lowers blood pressure (BP) in patients with hypertension.
• The mechanism underlying that improvement is unknown.
• 50 healthy subjects performed 10 min training each day for 6 weeks.
• BP dropped in subjects trained with large intrathoracic pressures.
• BP was unaffected in subjects trained with large lung volumes or paced breathing.

Inspiratory muscle training holds promise as a non-pharmacologic treatment that can improve respiratory muscle strength, reduce blood pressure, and improve autonomic balance in hypertensive patients. There is a gap in knowledge regarding the specific respiratory stimulus that gives rise to these favorable outcomes. We implemented five respiratory training protocols that differed in the magnitude and direction of the lung volumes and/or intrathoracic pressures generated by subjects in training. Normotensive adults were randomly assigned to each group and trained daily for 6 weeks. Pre-post and weekly measures of blood pressure showed significant declines in systolic [−8.96 mmHg (95% CI, 7.39–10.53)] and diastolic [−5.25 mmHg (95% CI, 3.67–6.83)] blood pressures for subjects who trained with large positive or negative intrathoracic pressures. Subjects who trained with modest intrathoracic pressures or large lung volumes saw no improvement in blood pressure (P > 0.3). Large intra-thoracic pressures are the specific respiratory stimulus underpinning breathing training related improvements in blood pressure.