Please cite this article in press as: Verges, S., et al., Effects of different respiratory muscle training regimes on fatigue-related variables during volitional hyperpnoea. Respir. Physiol. Neurobiol. (2009), doi:10.1016/j.resp.2009.09.005 ARTICLE IN PRESS G Model RESPNB-1277; No. of Pages 9 Respiratory Physiology & Neurobiology xxx (2009) xxx–xxx Contents lists available at ScienceDirect Respiratory Physiology & Neurobiology journal homepage: www.elsevier.com/locate/resphysiol Effects of different respiratory muscle training regimes on fatigue-related variables during volitional hyperpnoea Samuel Verges ∗ , Andrea S. Renggli, Dominic A. Notter, Christina M. Spengler Exercise Physiology, Institute for Human Movement Sciences, ETH Zurich, and Institute of Physiology and Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland article info Article history: Accepted 7 September 2009 Keywords: Respiratory muscle endurance training Hyperpnoea Respiratory muscle fatigue Respiratory sensations abstract We compared the effects of the most commonly used respiratory muscle (RM) training regimes: RM endurance training (RMET; normocapnic hyperpnoea) and inspiratory resistive training (IMT), on RM performance. Twenty-six healthy men were randomized into 3 groups performing 4 weeks of RMET, IMT or sham-training. Lung function, RM strength and endurance were tested before and after training. RM fatigue during intermittent hyperpnoea was assessed by twitch oesophageal (P oes,tw ) and gastric pressures with cervical and thoracic magnetic stimulation. Respiratory sensations (visual analogue scale, 0–10) and blood lactate concentrations ([La]) were assessed during hyperpnoea. RMET increased maximal voluntary ventilation while IMT increased maximal inspiratory pressure. Both RMET and IMT increased vital capac- ity and RM endurance, but only RMET improved the development of inspiratory muscle fatigue (from -31% to -21% P oes,tw ), perception of respiratory exertion (4.2 ± 0.1 to 2.3 ± 2.3 points) and [La] (1.8 ± 0.4 to 1.3 ± 0.3 mmol l -1 ) during hyperpnoea. Whether these specific RMET-induced adaptations observed during hyperpnoea would translate into greater improvements in exercise performance compared to IMT remains to be investigated. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Respiratory muscle training has been used to improve respira- tory muscle function in healthy subjects [for review see: (Sheel, 2002)] and in patients [for review see: (Geddes et al., 2005; Padula and Yeaw, 2007)]. In studies with healthy subjects, two different forms of respiratory muscle training have mainly been employed: (i) respiratory muscle endurance training in the form of volitional normocapnic hyperpnoea [RMET (Leith and Bradley, 1976; Boutellier et al., 1992; Boutellier and Piwko, 1992; McMahon et al., 2002; Holm et al., 2004; Leddy et al., 2007; Wylegala et al., 2007)] and (ii) inspiratory muscle training using exter- nal resistances or threshold loads [IMT (Leith and Bradley, 1976; Suzuki et al., 1993; Volianitis et al., 2001; Romer et al., 2002a; Gething et al., 2004; Brown et al., 2008)]. While RMET involves high-speed/low-resistance contractions of both inspiratory and expiratory muscles, IMT employs resistance-training principles with high-resistance/low-speed contractions and is confined to inspiratory muscles. ∗ Corresponding author at: REX-S Laboratory, Exercise Research Unit, Hôpital Sud, Avenue Kimberley, 38 434 Echirolles, France. Tel.: +33 6 70 39 57 73; fax: +33 4 76 76 56 17. E-mail address: sverges@chu-grenoble.fr (S. Verges). From ‘general’ skeletal muscle training it is well known that the ability of a training stimulus to improve performance in a target task depends on specific structural and functional adapta- tions occurring, i.e. the specificity of the muscle groups involved, contraction characteristics (e.g. velocity, strength), neuromuscular coordination and metabolic requirements (Faulkner, 1984). Thus, because RMET and IMT involve to some extent, different mus- cle groups, muscle loads and speeds of contraction, these training methods are likely to cause different respiratory muscle adapta- tions, as suggested by specific functional adaptations. Examples of these adaptations are the increased capacity to perform intensive hyperpnoea after RMET only (Leith and Bradley, 1976; Boutellier et al., 1992; Boutellier and Piwko, 1992; McMahon et al., 2002; Holm et al., 2004; Leddy et al., 2007; Wylegala et al., 2007), and the increased maximal inspiratory mouth pressure generation after IMT only (Leith and Bradley, 1976; Suzuki et al., 1993; Volianitis et al., 2001; Romer et al., 2002a; Gething et al., 2004; Brown et al., 2008). Hence the specific muscular adaptations to RMET and IMT may have different effects on muscle fatigue and endurance performance as well as physiological responses (e.g. lactic acid pro- duction, respiratory sensations) during hyperpnoea. Currently, respiratory muscle fatigue is believed to affect whole- body endurance performance by eliciting a metaboreflex (Dempsey et al., 2006). This reflex is thought to originate in fatigued respira- tory muscles by stimulating type IV afferents as a result of increased local metabolites, e.g. lactate concentration, which then increase 1569-9048/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.resp.2009.09.005