Context. Anecdotal reports suggest elite sports clubs combine lower body positive pressure (LBPP) rehabilitation with a hypoxic stimulus in order to maintain or increase physiological and metabolic strain, which are reduced during LBPP. However the effects of hypoxia on cardiovascular and metabolic response during LBPP rehabilitation is unknown.
Objective. Evaluate the use of normobaric hypoxia as a means to increase physiological strain during body weight supported (BWS) running.
Design. Cross over study.
Setting. Controlled laboratory.
Participants. Seven familiarized males (mean ± SD; age, 20 ± 1 years; height, 1.77 ± 0.05 meters; mass, 69.4 ± 5.1 kg; haemoglobin 15.2 ± 0.8 g.dL-1). completed a normoxic and hypoxic (FIO2 = 0.14) trial, during which they ran at 8km.hr-1 on an Alter-GTM treadmill with 0, 30 and 60% BWS in a randomised order for 10 minutes interspersed with 5 minutes of recovery.
Main outcome measures. Arterial oxygen saturation, heart rate, oxygen delivery and measurments of metabolic strain via indirect calorimetry.
Results Hypoxic exercise reduced SpO2 and elevated heart rate at each level of BWS compared to normoxia. However, the reduction in SpO2 was attenuated at 60% BWS compared to 0% and 30% and consequently oxygen delivery was better maintained at 60% BWS.
Conclusion. Hypoxia is a practically useful means of increasing physiological strain during BWS rehabilitation. In light of the maintenance of SpO2 and oxygen delivery at increasing levels of BWS, fixed haemoglobin saturations rather than a fixed altitude is recommended in order to maintain an aerobic stimulus.