Pulmonary mechanics and entrainment of respiration and stroke rate during rowing

During rowing, the respiratory musculature is confronted with dual demands: assisting the propulsive force generation and as the effector for ventilatory control. We determined the pulmomechanical and breathing pattern features of rowing-induced hyperpnea in five national class rowers (18 years old). Each subject performed incremental exercise on a mechanically braked rowing ergometer. Power was increased by 50 W each 3 min, from 150 W to 350 W. Breathing was through a low-resistance, ultrasonic flow-sensing device. Respired gas concentrations were measured by mass spectrometry. Intrapleural pressure (Pp1) was monitored by an esophageal balloon. Ventilation (VE) increased by increasing tidal volume (VT) at constant breathing frequency (fb). Above approximately 701.min-1 there was little change in VT and further increase in VE was dominated by fb. Two breathing patterns were identified: (1) one expiration per stroke and one inspiration during recovery and (2) one complete breath during stroke and one breath during recovery. Stroke frequency (fs) and fb increased in concert, i.e., all subjects entrained their breathing. Pp1 indicated dynamic airway compression during exhalation at high work rates and also that VT did encroach upon the flat part of the compliance curve. With the constrained VT, the demand for increased fb to effect the hyperpneic response at high work rates may result in an entrainment of the stroke frequency to that of breathing.