Respiratory Physiology & Neurobiology 152 (2006) 128–142 Rapid increases in ventilation accompany the transition from passive to active movement Harold J. Bell a , James Duffin a,b,∗ a Department of Physiology, University of Toronto, Medical Sciences Building, 1 King’s College Circle, Toronto, Ont., Canada M5S 1A8 b Department of Anaesthesia, University of Toronto, Medical Sciences Building, 1 King’s College Circle, Toronto, Ont., Canada M5S 1A8 Accepted 28 July 2005 Abstract We used a novel movement transition technique to look for evidence of a rapid onset drive to breathe related to the active component of exercise in humans. Ten volunteers performed the following transitions in a specially designed tandem exercise chair apparatus: rest to passive movement, passive to active movement, and rest to active movement. The transition from rest to active exercise was accompanied by an immediate increase in ventilation, as was the transition from rest to passive leg movement (Δ = 6.06 ± 1.09 l min -1 , p < 0.001 and Δ = 3.30 ± 0.57 l min -1 , p = 0.002, respectively). When subjects actively assumed the leg movements, ventilation again increased immediately and significantly (Δ = 2.55 ± 0.52 l min -1 , p = 0.032). Ventilation at the first point of active exercise was the same when started either from rest or from a background of passive leg movement (p = 1.00). We conclude that the use of a transition from passive to active leg movements in humans recruits a ventilatory drive related to the active component of exercise, and this can be discerned as a rapid increase in breathing. © 2005 Elsevier B.V. All rights reserved. Keywords: Ventilation; Exercise; Passive movements; Humans 1. Introduction The ventilatory response to the onset of moder- ate intensity, constant load exercise in humans has been well described and reviewed elsewhere (Mateika and Duffin, 1995; Ward, 2000). In particular, a rapid ∗ Corresponding author. Tel.: +1 416 978 6379; fax: +1 416 978 4940. E-mail address: j.duffin@utoronto.ca (J. Duffin). increase in breathing at exercise onset is a feature that has been recognized in the respiratory response for nearly a century (Krogh and Lindhard, 1913). Precisely how respiratory drive is increased abruptly at exer- cise onset remains a topic of active debate. In current literature ‘central motor command’ and ‘afferent feed- back’ are two mechanisms believed to be of principal importance in providing a drive to breathe at the onset of exercise, though alternative mechanisms have been proposed. Central command is a mechanism whereby 1569-9048/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.resp.2005.07.008