Hypoxia training is something that is gaining more mainstream recognition in the strength and conditioning community, but it is something that has been used extensively by endurance athletes. It has proven benefits for improving aerobic capacity, as well as anaerobic capacity through lower VO2 and atrial oxygen saturation, and increases in carbohydrate utilization and blood lactate concentrations. Long term effects of hypoxic (H) training and acute physiological effects have been well studied but post-exercise physiological responses have not been studied as thoroughly. Authors wanted to run a study that was closer to the physiological demands of the endurance athlete’s sport and emphasized studying the post-exercise effects on physiology.
What They Did:
They took 9 elite endurance runners and tested them in both H and normoxic (N) conditions. Testing was performed near their maximal VO2 (90%) and total time working was 60+ minutes, much closer to the type of work that these athletes do in competition and training. Their protocol included a 30-minute interval period (10x3 min at 95% VO2max w/ 60 sec active rest at 60% VO2max) and a 30-minute continuous running period at 85% VO2max (after a 10 min recovery period). Following these two segments, 120 minutes was given post exercise to observe physiological responses prior to a time to exhaustion test (TTE).
Speeds were lower and higher lactate levels were measured in H conditions versus N conditions, as was expected. VO2 and SpO2 were lower in the H condition versus N. Minute ventilatory volume (VE) increased in H during the intervals a lot more than in N but the RPE stayed relatively the same. Serum myoglobin was greater in N versus H and interestingly, during the time to exhaustion test, the H condition lasted significantly longer than the N condition.
So What? Why do I Care?:
Focusing on the levels of IL-6 and serum myoglobin, both markers of mechanical stress to the body, they were found to be significantly lower in the H condition compared to N. This, combined with the similar RPE during exercise would suggest that H is causing greater metabolic strain to the system then mechanical strain but delivering similar benefits with regards to the physiological changes occurring in the body. Normally, lactate transport work would require a large amount of mechanical stress to the body in order to help get it to a point where the lactate transport work begins (think about sleds for time or repeated sprints and you know what I’m getting at). With hypoxic training, you bring the body to a similar or greater level of lactate stress without the corresponding muscular work and fatigue, as demonstrated by the increased lactate levels but similar RPE, also the increased TTE test times in the H group. Provided this is true for other athletes outside of runners, if you are working with an athlete who might not be in a phase where large amounts of lactate threshold work would be wise, this could be a work around, keeping them muscularly fresh but still getting the metabolic work in. This could also be beneficial in rehabilitation, allowing a greater diversity of system training while an athlete recovers from a musculoskeletal injury and intensity needs to be limited.
Sumi, D., Kojima, C., & Goto, K. (2018) Impact of Endurance Exercise in Hypoxia on Muscle Damage, Inflammatory Response and Performance Responses. Journal of Strength and Conditioning Research. 32(4), 1053-1062