Abstract

Background. Hypoxia and hyperoxia can affect the acute psycho-physiological response to exercise. Recording various perceptual responses to exercise is of particular importance for investigating behavioural changes to physical activity, given that the perception of exercise-induced pain, discomfort or unpleasure, and a low level of exercise enjoyment are commonly associated with a low adherence to physical activity. Therefore, this study aimed to compare the acute perceptual and physiological responses to aerobic exercise under intermittent hypoxia-hyperoxia (IHHT), hypoxia-normoxia (IHT), and sustained normoxia (NOR) in young recreational active healthy males. Methods. Using a randomized, single-blinded, crossover design, 15 males (age: 24.5±4.2 yrs) performed 40min of submaximal constant-load cycling (at 60% peak oxygen uptake, 80rpm) under IHHT (5x4 min hypoxia and hyperoxia), IHT (5x4 min hypoxia and normoxia) and NOR. Inspiratory fraction of oxygen during hypoxia and hyperoxia was set to 14% and 40%, respectively. Heart rate (HR) and muscle oxygenation (total tissue (tHb) and oxygenated haemoglobin concentration (S_mO₂)) of the right vastus lateralis muscle were continuously recorded during cycling. Participants’ peripheral oxygen saturation (S_pO₂) and perceptual responses (i.e., perceived motor fatigue, effort perception, perceived physical strain, affective valence, arousal, motivation to exercise, and conflict to continue exercise) were surveyed prior, during (every 4min), and after cycling. Prior to and after exercise, peripheral blood lactate concentration (BLC) was determined. Exercise enjoyment was ascertained after cycling. For statistical analysis, repeated measures analyses of variance were conducted. Results. No differences in the acute perceptual responses were found between conditions (p≥0.059, η_p²≤0.18), while the physiological responses differed. Accordingly, S_pO₂ was higher during the hyperoxic periods in the IHHT compared to the normoxic periods in the IHT (p<0.001, η_p²=0.91). Moreover, HR (p=0.005, η_p²=0.33) and BLC (p=0.033, η_p²=0.28) were higher during IHT compared to NOR. No differences between conditions were found for percentual changes in tHb (p=0.684, η_p²=0.16) and S_mO₂ (p=0.093, η_p²=0.16). Conclusion. IHT is associated with a higher physiological response and metabolic stress, while IHHT did not lead to an increase in HR and BLC compared to NOR. In addition, compared to IHT, IHHT seems to improve reoxygenation indicated by a higher S_pO₂ during the hyperoxic periods. However, there were no differences in perceptual responses and ratings of activity enjoyment between conditions. These results suggest that replacing normoxic by hyperoxic reoxygenation-periods during submaximal constant-load cycling under intermittent hypoxia reduced the exercise-related physiological stress but had no effect on perceptual responses and perceived activity enjoyment in young recreational active healthy males.