Mechanical-ventilatory responses to peak and ventilation-matched upper- versus lower-body exercise in normal subjects

Abstract

Copyright © 2019 The Authors. The aim of this study was to determine the extent to which the mechanical ventilatory responses to upper-body exercise are influenced by task-specific locomotor mechanics. Eight healthy men (mean ± SD: age, 24 ± 5 years; mass, 74 ± 11 kg; and stature, 1.79 ± 0.07 m) completed two maximal exercise tests, on separate days, comprising 4 min stepwise increments of 15 W during upper-body exercise (arm-cranking) or 30 W during lower-body exercise (leg-cycling). The tests were repeated at work rates calculated to elicit 20, 40, 60, 80 and 100% of the peak ventilation achieved during arm-cranking (urn:x-wiley:09580670:media:eph12488:eph12488-math-0001). Exercise measures included pulmonary ventilation and gas exchange, oesophageal pressure-derived indices of respiratory mechanics, operating lung volumes and expiratory flow limitation. Subjects exhibited normal resting pulmonary function. Arm-crank exercise elicited significantly lower peak values for work rate, O2 uptake, CO2 output, minute ventilation and tidal volume (p < 0.05). At matched ventilations, arm-crank exercise restricted tidal volume expansion relative to leg-cycling exercise at 60% urn:x-wiley:09580670:media:eph12488:eph12488-math-0002 (1.74 ± 0.61 versus 2.27 ± 0.68 l, p < 0.001), 80% urn:x-wiley:09580670:media:eph12488:eph12488-math-0003 (2.07 ± 0.70 versus 2.52 ± 0.67 l, p < 0.001) and 100% urn:x-wiley:09580670:media:eph12488:eph12488-math-0004 (1.97 ± 0.85 versus 2.55 ± 0.72 l, p = 0.002). Despite minimal evidence of expiratory flow limitation, expiratory reserve volume was significantly higher during arm-cranking versus leg-cycling exercise at 100% urn:x-wiley:09580670:media:eph12488:eph12488-math-0005 (39 ± 8 versus 29 ± 8% of vital capacity, p = 0.002). At any given ventilation, arm-cranking elicited greater inspiratory effort (oesophageal pressure) relative to thoracic displacement (tidal volume). Arm-cranking exercise is sufficient to provoke respiratory mechanical derangements (restricted tidal volume expansion, dynamic hyperinflation and neuromechanical uncoupling) in subjects with normal pulmonary function and expiratory flow reserve. These responses are likely to be attributable to task-specific locomotor mechanics (i.e. non-respiratory loading of the thorax).