Hyperoxic Training: Going Deep to Go Fast
Over the past decade, altitude and hypoxic training have progressively become better known and even common among elite cyclists and other endurance athletes. From the complete opposite spectrum comes the latest reverse twist on altitude training, and that is to use hyperoxia, or training in a higher-than-normal oxygen environment, as a ergogenic aid…
With the off-season approaching in the Northern Hemisphere, I figure that it might be fun to explore what new technologies or training ideas might be on the horizon in the years to come. Some of the articles might involve ideas that seem ridiculous or impractical now for most of us, but that’s what was once said about things as mundane nowadays as a portable heart rate monitor (Francesco Moser’s use of a bulky wired HRM for his world hour record in 1984 was considered revolutionary, and helped to popularize the concept of scientific training).
One such idea is the concept of hyperoxic training, doing your hard workouts with a higher-than-normal amount of oxygen.
Altitude Physiology 101
The whole concept of exercise at altitude really first boomed in the period prior to the 1968 Olympics in Mexico City. Since that time, riders from Eddy Merckx in the 1970s, Francesco Moser in 1984 (both hour records in Mexico City), and most recently Chris Hoy in 2007 (Kilo record attempt at La Paz, Bolivia at 3500 m elevation) have utilized the lower air resistance at altitude in their attempts at peak performances. I recently discussed the timing of arrival to a competition at altitude.
High altitude is not an all-encompassing panacea for performance, however. The tradeoff for the lowered air resistance is increasing difficulty in getting sufficient oxygen at altitude. While the percentage of oxygen in air remains constant at 20.93% throughout Earth’s atmosphere, the lower barometric pressure at high elevations (barometric pressure is 760 mm Hg at sea level, and ~250 mm Hg at the summit of Everest at 8,848 m) means that the actual partial pressure of oxygen is significantly lower in places like Boulder than in either my previous base in Halifax (sea level) or new home in the Niagara region (200 m).
Where this comes into play with athletes, of course, is the concept of altitude training, whereby living and exercising at altitude was first systematically employed in the post-Mexico City years. The basis of altitude training is simple. Because the human body is astoundingly good at adapting to the stresses placed upon it, the decreased oxygen availability stimulates an increase in hemoglobin and red blood cells to compensate. Upon return to sea level, the increased oxygen carrying capacity translates into higher aerobic capacity. Of course, this is also the identical physiological basis underlying blood doping and EPO use, leading to the somewhat ethically defendable but logistically ridiculous notion floated by WADA a few years back about banning hypoxic training.
Live High Train Low
The original design of altitude training has been to exercise and live at altitude. However, the common complaint of most athletes is a greatly reduced ability to both train hard and recover from hard workouts. Therefore, while cardiovascular benefits may occur, this may be negated by the decreased exercise stimulus.
The advent of hypoxic tents and facilities has made logistically feasible the Live High Train Low regimen. In this paradigm, the exercise stimulus is maximized by training at lower altitudes and having no impairment from decreases in oxygen availability (Train Low). Then passive exposure for the remaining time maximizes cardiovascular adaptations (Live High). Theoretically the best of all worlds!
Going Deep: Early Work
From the “if a little is good, more must be better” philosophy of training and scientific research, the concept of hyperoxic training becomes quite logical. Because the purpose of “Train Low” is to maintain training stimulus by not impacting oxygen availability, then it appears logical that training in a higher-than-normal (hyperoxic) environment might permit greater than normal workloads, and therefore greater than normal training stimulus.
I first got a whiff of this scent in the scientific nostril back in 1997, at the end of my Ph.D. studies and attending the big American College of Sports Medicine conference for the first time. It was held in Denver that year, and a group from the USOC was presenting some work they were test-piloting on their athletes. Specifically, they used their B-string track team pursuit riders as guinea pigs prior to the Atlanta Olympics (no way were you going to risk your A-team on unproven science!).
I can’t recall the exact methodology and such, but I do remember that they reported the subjects could put out massive wattages while training in hyperoxia, far higher than what they could sustain in a normal (normoxic) environment. However, the scientists concluded that hyperoxic training didn’t ultimately provide an ergogenic aid, because the athletes all exhibited overly high levels of fatigue and symptoms of overtraining.
Hyperoxia: More Recent Research
Rather than being ineffective, the above preliminary report now seem more a case of not understanding how to implement a new and unexplored training tool than an actual lack of benefit. Scientific progress occurs by continually probing ideas and refining them, and a 2005 Canadian study in Medicine and Science in Sports and Exercise studies the effects of hyperoxic training on cardiorespiratory responses to exercise and also execise performance itself (Perry et al. 2005).
Specific study details:
• Nine subjects who were active but not specifically trained cyclists.
• Each subject performed six weeks of interval training in a normoxic (21% O2) and hyperoxic (60% O2) environment. In between the two training periods, the subjects were inactive and detrained for a period of 12 weeks. The long (24 week) time commitment likely explains why trained or elite cyclists were not employed, as it would be nearly impossible to convince high-level athletes to give up control of their training for 6 months and essentially and entire season!
• Each 6 weeks of training consisted of 18 (3x/wk) workouts. Each workout consisted of 10×4 min intervals at 80% VO2max with 2 min recovery.
• Workload throughout the training periods were adjusted (generally upwards) to maintain a consistent heart rate during efforts.
• VO2max and ride time to exhaustion at 90% VO2max, and also physiological responses to a ride at 80% VO2max, was tested and compared pre- and post-training for both normoxic and hyperoxic groups.
Key Study Findings
• An average of 8.1% greater power output was required during hyperoxia to maintain the same heart rates in the two conditions.
• A slight but non-significant trend towards a higher VO2max post-training with hyperoxia.
• Both normoxic and hyperoxic training resulted in increased tolerance time to 90% VO2max workload, with a significantly greater increase with hyperoxia.
• Heart rate max did not change following either normoxic or hyperoxic training.
• Both heart rate and ventilation at 80% VO2max decreased with both normoxic and hyperoxic training, with no difference between the two training programs.
Training studies with animals are difficult enough, even with the much higher level of control possible when you house and care for animals in the lab (they don’t go on crazy diets, do extra training outside of your study protocol, get too little sleep or get stressed out from projects or midterms!). Doing such an intensive and prolonged training study on humans is no mean feat at all, such that using relatively non-specific subjects is a realistic requirement.
The 8.1% higher power output to maintain the same heart rate clearly demonstrates that the training stimulus is indeed much higher with hyperoxia than at normal oxygen levels. At the same time, the improved ride time to exhaustion at 90% VO2max, along with the lower physiological strain at 80% VO2max, clearly point to an ergogenic potential for hyperoxic training.
This vein of research appears to be full of unanswered questions and promise. For example, it is somewhat unfortunate that no blood parameters, even relatively basic ones such as hemoglobin and hematocrit, were taken. Therefore, the cardiovascular adaptations to hyperoxic training remains unknown, along with blood markers for immune function, muscle damage, etc.
However, given results such as this, it’s possible that the future of altitude training lies in “Live High Train Very Low,” maximizing both hypoxic and training stimulus! Stay tuned in the years to come!
Perry, CGR, J Reid, W Perry, and BA Wilson. Effects of hyperoxic training on performance and cardiorespiratory response to exercise. Med Sci Sports Exerc 37:1175-1179, 2005.
Stephen Cheung is an Associate Professor of Kinesiology and a Canada Research Chair in Environmental Ergonomics at Brock University, with a research specialization in the effects of thermal stress on human physiology and performance. He can be reached for comments at [email protected].