Acute and short-term normobaric hypoxic conditioning on psycho-physiological responses in obese populations
Creators: name: Hobbins, Liam
Publisher: name: London South Bank University
Year: 2020

description: This thesis investigated the psycho-physiological responses of obese individuals during and following acute and short-term hypoxic conditioning, including both passive and active modalities. Study one determined psycho-physiological responses to passive hypoxic conditioning (FiO2= 12.0%) consisting of varying hypoxic and normoxic cycles in obese individuals. It was found that perceptions of breathlessness following short (15 × 2 mins hypoxia/2 mins normoxia) cycles was lowest (-7%) for up to 60 mins post-exposure compared to long cycles (5 × 6 mins hypoxia/6 mins normoxia), whilst the extent of desaturation in arterial oxygen satura tion was greater in the latter than the former (-4%). The fndings of this study later informed the interval work/rest duration of exercising in hypoxia for obese individuals. Study two assessed psycho-physiological responses of trained runners during a perceptually regulated interval running session (4 × 4 mins at a rating of perceived exertion equal to 16, 3mins recovery) in hypoxic (FiO2 = 15.0%) and normoxic conditions. The main findings show that a slower treadmill velocity (-6%) was required to maintain a rating of perceived exertion equal to 16 in hypoxia than normoxia. Whilst physiological responses were matched between conditions (i.e., heart rate and muscle oxygenation), exercise-related sensations (i.e., perceived recovery [-21%], motivation [-21%], breathlessness [+22%%], limb discomfort [+11%%] and pleasure [-31%]) were negatively impacted more so during hypoxia compared to normoxia. The findings of this study provided an intial insight regarding the influence of hypoxia on the perceptually-regulated exercise model in trained runners prior to utilisation in an obese population. Study three assessed psycho-physiological responses of obese individuals during a perceptually-regulated interval walking session (15 × 2 mins walking, 2 mins recovery, based on the findings of study one) in hypoxic (FiO2 = 13.0%) and normoxic conditions. Further, during an additional third condition, the psycho-physiological responses from hypoxia were isolated with the velocity selected during this trial matched in normoxic conditions. Similar to study three, a slower treadmill velocity (-2%) was required to maintain a rating of perceived exertion equal to 14 in hypoxia than normoxia. Physiological responses were more pronounced during hypoxia compared to normoxia (i.e., higher heart rate [+6%] and lower muscle oxygenation [-6%]), whilst perceptions of limb discomfort were lower (-21%) in the former than the latter. In the absence of hypoxia at the same velocity, perceptions of limb discomfort were matched to perceptually-regulated walking in hypoxia, but the physiological stress was lower (i.e., heart rate [-5%]). The findings of this study provided indication of the acute effects of perceptually-regulated interval walking in hypoxia prior to implementation of this protocol design on a regular, short-term basis. Study four examined the psycho-physiological responses of obese individuals to a short-term training intervention (utilising the same session protocol of study three, eight sessions in two weeks) in hypoxic (FiO2 = 13.0%) and normoxic conditions. A similar perceptually-regulated velocity, physiological stress (i.e., heart rate) and exercise-related sessions (i.e., perceived recovery, motivation, breathlessness, limb discomfort and pleasure) were recorded during training between conditions. Improvements in perceived mood state (+12%), exercise-selfefficacy (+11%) and energy expenditure (+10%) were reported after training independent of condition, whilst resting blood glucose levels were only enhanced after hypoxic training (-15%). Collectively, obese individuals may benefit in terms of psycho-physiological responses from exercising at a perceptually-regulated intensity in hypoxia more so than normoxia. These benefits (acute and short-term) could be potentiated largely due to the optimisation of cycle variations of hypoxia/normoxia and exercise/rest durations.