Effects of Varying Levels of Hypoxia on Muscle Oxygenation During Leg Exercise

Michael Rees

Document Type

Presentation

Journal/Book Title/Conference

USU Student Showcase

Publication Date

4-2014

Faculty Mentor

John Davis, Dale Wagner

Abstract

Previous studies have looked at muscle tissue oxygenation under a wide range of conditions including temperature extremes and in various disease states. The purpose of this study was to examine the muscle tissue saturation response under varying hypoxia conditions during different intensities of aerobic exercise, including walking and running. Eight healthy, fit participants were recruited and completed testing randomly in three different conditions simulating varying levels of hypoxia: 9000 ft (MID), 16000 ft (HIGH) and while breathing ambient air (LOW). A Higher Peak Mag hypoxic generator was used to produce normobaric hypoxia . During the HIGH, MID, and LOW conditions subjects walked for 5 min at 3 mph and then ran for 5 min at 6 mph on a motorized treadmill. Near-infrared spectroscopy (Portamon, Artinis Inc.) was used to measure oxygenated hemoglobin, deoxygenated hemoglobin, total hemoglobin, and tissue saturation index (TSI) throughout the exercise. The Portamon was placed over the vastus lateralis and secured. TSI is used as an index of muscle tissue oxygenation, and the slope of the decline in TSI was determined and used to quantify the muscle oxygenation response. Overall, TSI decreased at a greater rate for running than walking. The decline in TSI was greatest in the HIGH running condition (-0.040 + .016) compared to the MID (.015 +.004) and LOW conditions (-.030 +.023). These data suggest that muscle oxygenation declined at the fastest rate with running at the greatest level of hypoxia. This probably reflects a greater utilization of oxygen under severe hypoxic conditions in the muscle. Furthermore, running during all levels of hypoxia produced a greater rate of oxygen utilization than walking. Taken together, running at high altitude provides the greatest hypoxic stress to exercising leg muscle.

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