Respiratory Physiology & Neurobiology 188 (2013) 102–112 Contents lists available at SciVerse ScienceDirect Respiratory Physiology & Neurobiology j our na l ho me pa g e: www.elsevier.com/locate/resphysiol Alveolar gas exchange, oxygen delivery and tissue deoxygenation in men and women during incremental exercise Juha E. Peltonen a,b,∗ , Harriet Hägglund a , Tiina Koskela-Koivisto c , Anne S. Koponen a , Jyrki M. Aho b , Antti-Pekka E. Rissanen a , J. Kevin Shoemaker d , Aila Tiitinen c , Heikki O. Tikkanen a,b a Department of Sports and Exercise Medicine, Institute of Clinical Medicine, University of Helsinki, Helsinki, Finland b Foundation for Sports and Exercise Medicine, Clinic for Sports and Exercise Medicine, Helsinki, Finland c Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Helsinki, Finland d Neurovascular Research Laboratory, School of Kinesiology, Western University, London, ON, Canada a r t i c l e i n f o Article history: Accepted 13 May 2013 Keywords: Near infrared spectroscopy Oxygen uptake Cardiac output Total hemoglobin mass Blood volume a b s t r a c t We investigated whether leg and arm skeletal muscle, and cerebral deoxygenation, differ during incre- mental cycling exercise in men and women, and if women’s lower capacity to deliver O 2 affects tissue deoxygenation. Men (n = 10) compared to women (n = 10), had greater cardiac output, which with greater hemoglobin concentration produced greater absolute (QaO 2 ) and body size-adjusted oxygen delivery (QaO 2i ) at peak exercise. Despite women’s lower peak QaO 2 , their leg muscle deoxygenation was similar at a given work rate and QaO 2 , but less than in men at peak exercise (tissue saturation index -27.1 ± 13.2% vs. -11.8 ± 5.7%, P < 0.01; [deoxyhemoglobin] 15.03 ± 8.57 M vs. 3.73 ± 3.98 M, P < 0.001). At peak exercise, oxygen uptake was associated both with QaO 2 and leg muscle deoxygenation (both P < 0.01). Arm muscle and cerebral deoxygenation did not differ between sexes at peak exercise. Thus, both high O 2 delivery and severe active muscle deoxygenation are determinants of good exercise performance, and active muscle deoxygenation responses are regulated partly in a sex-specific manner with an influence of exercise capacity. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Active muscle deoxygenation, representing regional mismatch between O 2 delivery and O 2 utilization, increases during incre- mental exercise (Belardinelli et al., 1995; Bhambhani et al., 1998; Costes et al., 1996; Peltonen et al., 2009; Subudhi et al., 2007). However, studies comparing exercise-induced tissue deoxygen- ation between sexes are rare, with limited attention paid on women and sex-specific variation in these responses. The sparse existing data indicate lesser active muscle deoxygenation at the same rela- tive exercise intensity in women compared with men (Bhambhani et al., 1999), and no difference in the rate of active muscle deoxy- genation or amplitude at peak exercise between sexes (Bhambhani et al., 1998). Inactive arm muscle shows considerable deoxygen- ation during leg cycling (Ogata et al., 2007; Peltonen et al., 2012) and may coarsely reflect regional blood flow regulation during exer- cise in terms of supporting blood pressure (Saito et al., 1997) with ∗ Corresponding author at: Department of Sports and Exercise Medicine, Insti- tute of Clinical Medicine, University of Helsinki, Paasikivenkatu 4, 00250 Helsinki, Finland. Tel.: +358 9 4342100; fax: +358 9 490809. E-mail addresses: juha.peltonen@helsinki.fi, juha.peltonen@hula.fi (J.E. Peltonen). a possible “respiratory steal phenomenon” (Legrand et al., 2007) and favoring blood flow to the active muscle (Secher and Volianitis, 2006). In addition, cerebral oxygenation increases during exercise of mild to moderate intensity, while during intense whole body exercise, cerebral oxygenation is reduced (Peltonen et al., 2009; Subudhi et al., 2007). Although it is unlikely that changes in cere- bral oxygenation limit exercise performance at sea level (Billaut et al., 2010; Peltonen et al., 2009; Subudhi et al., 2007), cerebral blood flow and oxygenation during exercise are dependent on nor- mal response in cardiac output (Ide and Secher, 2000; Koike et al., 2004) and dynamic cerebral autoregulation that may be impaired by exhaustive exercise (Ogoh et al., 2005). To our knowledge, stud- ies comparing inactive muscle and cerebral oxygenation during exercise in men and women are non-existent. To fully evaluate tissue oxygenation in both sexes, one should take into account that women exhibit several anatomic and physio- logic characteristics that distinguish their acute exercise responses from those of men. Women are smaller than men, have less mus- cle mass, and more fat mass for a given body size (Charkoudian and Joyner, 2004). Importantly, aerobic capacity ( ˙ V O 2max ) is lower in women than in men (Hossack and Bruce, 1982; Mitchell et al., 1992; Ogawa et al., 1992). The differences in ˙ V O 2max between the sexes, when expressed as both l/min and ml/kg/min, have been partially accounted for by normalizing for fat-free mass (FFM) and training 1569-9048/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.resp.2013.05.014