Physiological Responses to Treadmill Running With Body Weight Support in Hypoxia Compared With Normoxia.
BACKGROUND
Anecdotal reports suggest elite sports clubs combine lower-body positive-pressure rehabilitation with a hypoxic stimulus to maintain or increase physiological and metabolic strain, which are reduced during lower-body positive pressure. However, the effects of hypoxia on cardiovascular and metabolic response during lower-body positive-pressure rehabilitation are unknown.


OBJECTIVE
Evaluate the use of normobaric hypoxia as a means to increase physiological strain during body-weight-supported (BWS) running.


METHODS
Crossover study.


METHODS
Controlled laboratory.


METHODS
Seven familiarized males (mean (SD): age, 20 (1) y; height, 1.77 (0.05) m; mass, 69.4 (5.1) kg; hemoglobin, 15.2 (0.8) g·dL-1) completed a normoxic and hypoxic (fraction of inspired oxygen [O2] = 0.14) trial, during which they ran at 8 km·h-1on an AlterG™ treadmill with 0%, 30%, and 60% BWS in a randomized order for 10 minutes interspersed with 5 minutes of recovery.


METHODS
Arterial O2saturation, heart rate, O2delivery, and measurements of metabolic strain via indirect calorimetry.


RESULTS
Hypoxic exercise reduced hemoglobin O2saturation and elevated heart rate at each level of BWS compared with normoxia. However, the reduction in hemoglobin O2saturation was attenuated at 60% BWS compared with 0% and 30%, and consequently, O2delivery was better maintained at 60% BWS.


CONCLUSIONS
Hypoxia is a practically useful means of increasing physiological strain during BWS rehabilitation. In light of the maintenance of hemoglobin O2saturation and O2delivery at increasing levels of BWS, fixed hemoglobin saturations rather than a fixed altitude are recommended to maintain an aerobic stimulus.
Ben J
BJ
Lee
Charles Douglas
CD
Thake
D001835:Body Weight; D018592:Cross-Over Studies; D005080:Exercise Test; D005081:Exercise Therapy; D006339:Heart Rate; D006454:Hemoglobins; D006801:Humans; D000860:Hypoxia; D008297:Male; D010092:Oximetry; D010101:Oxygen Consumption; D012420:Running / Q000502:physiology*; D055815:Young Adult
D006454:Hemoglobins
altitude; lower body positive pressure; rehabilitation