Inter-individual differences in breathing pattern at high levels of incremental cycling exercise in healthy subjects

Abstract

Interindividual differences in the rate of changes in tidal volume (VT) and respiratory frequency (fR) were examined during a maximal incremental cycling exercise. The gain of the inspiratory off-switch reflex was inferred from the VT vs. inspiratory duration (Ti) relationship. Some subjects also executed a static handgrip exercise, used as a “non-dynamic” exercise trial to study patterning of breathing.Above the ventilatory threshold (VTh), two patterns of response were identified: in group 1, the rate of change in VT significantly increased, while in group 2 the breakpoint of ventilation solely resulted from fR increase. After the respiratory compensation point, a tachypnoeic response always occurred. A leftward shift of the VT vs. Ti relationship, i.e., an inspiratory off-switch reflex, was measured during the handgrip in group 2 subjects as well as marked fR variations.Our study identifies two different patterns of breathing after the VTh. The subjects who present a tachypnoeic response to exercise above the VTh have a higher sensitivity to pulmonary inflation and their tachypnoeic response was ubiquitous during a maximal handgrip test.