Author(s): TOWNSEND, N., QADDOURA, S., HAMAD, N., Institution: HAMAD BIN KHALIFA UNIVERSITY, Country: QATAR, Abstract-ID: 1195

INTRODUCTION:
Exercise in hypoxia is an emerging therapeutic intervention used in the treatment of cardiometabolic diseases including obesity and type 2 diabetes. However, overweight women are prone to experiencing dyspnea on exercise (DoE), and thus may be susceptible to worsening DoE in hypoxia, since ventilation is typically increased. No studies have examined DoE though, during exercise in hypoxia matched for normoxic relative intensity. Therefore, the aim of this study was to investigate whether DoE is exacerbated during treadmill walking in overweight women, in hypoxia (HYPO) at equivalent relative intensity to normoxia (NORM).
METHODS:
Eleven sedentary females participated in this study (mean ± SD; BMI 31.2±3 kg/m2, age 24.8±4.2yr, body mass 79.6±7kg). A treadmill ramp test to determine gas exchange threshold (GET), respiratory compensation point (RCP) and VO2max was conducted in NORM (FiO2 ≈ 20.9%) and HYPO (FiO2 ≈ 14.0%). On separate days, a walking exercise session comprising 3x10 min intervals was conducted in NORM and HYPO at equivalent relative intensity in the heavy domain. Exertional dyspnea was assessed using Dyspnea-12 (D12), rating of perceived breathlessness (RPB), and rating of perceived unpleasantness (RPU) and the ventilatory responses were examined using exercise flow volume loops. A 2-way ANOVA was used to assess condition by time main effects and interaction. Effect size is reported as partial eta-squared.
RESULTS:
During incremental exercise, a progressive increase in all indices of DoE occurred during increasing intensity regardless of condition (all P<0.001; η_p^2>0.85). When relative intensity was matched during the 3x10 min interval sessions, there were no significant differences between conditions for D12, RPB, and RPU scales (all P>0.05; η_(p )^2<0.05). Similarly, no differences between NORM and HYPO were observed for VE, end expiratory lung volume, or inspiratory reserve volume (all P>0.05; η_(p )^2<0.05).
CONCLUSION:
Whilst DoE progressively increased during ramp incremental exercise irrespective of condition, there was not an independent effect of hypoxia when matched for relative exercise intensity. These perceptions were mirrored by the ventilatory response to exercise which also was no different between conditions. The results suggest that DoE is not affected by hypoxia independently of the ventilatory response to exercise. Thus, future studies examining the effect of hypoxia on cardiometabolic risk factors should control for DoE by matching relative exercise intensity.