By AJ Fisher, M.S., C.S.C.S.
2021 Sports and Health Sciences Master’s Degree Graduate
and Daniel G. Graetzer, Ph.D.
Faculty Member, School of Health Sciences
Intermittent hypoxic training (IHT) involves the intermittent inhalation of hypoxic (reduced oxygen) air interspersed with inhalations of ambient (normal oxygen) air, according to Frontiers in Neuroscience. The goal of intermittent hypoxic training is to improve athletic performance via stress-induced increases in the number of oxygen-carrying red blood cells, which will hopefully enhance energy utilization efficiency during competitions. In essence, it is essentially a legal version of what the U.S. Anti-Doping Agency calls “blood doping,” similar to endurance training at high altitudes or sleeping in altitude-simulating tents at night prior to sports events held at lower altitudes.
Hypoxia is a term often viewed negatively due to the catastrophic consequences of severe hypoxemia (low blood oxygen) on the brain and heart following a stroke, heart attack, or breathing emergency. As with any stressor, extreme doses can push the body into negative maladaptation and possible danger.
Exercise is certainly a stressor to the human body. Extreme sessions of exercise can cause overtraining (doing too much too soon with minimal rest), resulting in physical and mental maladaptation that overpower the positive adaptations that exercise normally creates.
Related: Overtraining and Hans Selye’s General Adaptation Syndrome
How Intermittent Hypoxic Training Affects the Body
Dosing is a critical variable that determines if a stressor causes positive versus negative outcomes. Intermittent hypoxic training involves exercising in a lower-oxygen environment that slightly lowers blood oxygen; this blood oxygen can be easily measured using a $30 pulse oximeter worn on a finger.
The mild lowering of blood oxygen during physical conditioning has many benefits. For instance, it can enhance athletic performance, mental cognition, brain plasticity and body composition as well as reduce the risk of cardiovascular disease.
Intermittent hypoxic training has been used by the military, Olympic athletes and professional sports organizations for decades. But how well does it work for the general population? The answer is “Probably, but more research on exact dosing is needed.”
Inhaling Air at a Lower Barometric Pressure in High-Altitude Environments
To exercise in a low-oxygen environment, you can climb a mountain to an altitude of about 2,500 meters (about 8,202 feet). This altitude is the optimal elevation to help the body adapt and achieve positive training benefits.
The correct dose of oxygen is key, however. If you climb too high, you could get altitude sickness. But if you don’t climb high enough, you would not achieve enough stimulation for your body to adapt and improve your physical fitness.
The human body requires a continuous supply of oxygen to the tissues to maintain the process of metabolism (the use of substrate for energy to maintain life-sustaining biological processes). The source of this oxygen is ambient air where the percentage of oxygen remains fixed at 20.93%, regardless of altitude.
An ascent to a higher altitude causes a reduction in the air’s pressure, inducing a corresponding decrease in the partial pressure of oxygen of the air you inhale. Because air carries weight, barometric pressure is higher at lower altitudes. Warm-temperature areas have lower barometric pressure than colder regions at the same altitude because hot air rises.
Also, barometric pressure changes on an almost daily basis due to shifts in wind patterns, air temperature and the rotation of the Earth. For instance, news reports of an impending reduction in barometric pressure indicate a cold front is coming, along with possible rain, snow or more serious weather conditions.
For example, with an ascent from sea level to the top of the tram at Utah’s Snowbird Ski Resort’s 11,000-foot Hidden Peak near Salt Lake City, Utah, the average barometric pressure decreases from about 760 mm Hg (millimeters of mercury) to about 510 mm Hg. Consequently, the change in altitude reduces the partial pressure of inhaled air from about 149 mm Hg to about 97 mm Hg.
Partial pressure of air after it has been inhaled into the lungs and is fully saturated with water vapor can be calculated as barometric pressure minus 47 times the percentage of oxygen in the ambient air. It can be calculated with this formula:
(Snowbird barometric pressure for an exerciser = ((510 – 47) x .2093) = 96.9 mm Hg
Related: High-Altitude Exercise: Improving Exercise Effectiveness
Using Technology to Simulate a Lower-Oxygen Training Environment
However, it’s not always necessary to ascend a mountain to work out with less oxygen. There are individual breathing units (made by Hypoxico) that allow you to breathe through a mask while exercising. You can also rent or buy a hypoxic chamber or have someone build you a lower-oxygen training environment so you can work out without being tethered to an oxygen mask.
What Happens in a Typical Intermittent Hypoxic Training Session
In a typical intermittent hypoxic training session, inhaling ambient oxygen at a lower-than-normal pressure causes the body’s blood oxygen saturation level to become lower. This oxygen saturation is a main driver of both short- and long-term adaptations during exercise.
Oxygen enters the body through the lungs where it binds with hemoglobin in the bloodstream for transport to the body’s tissues. A reduced partial pressure of oxygen impairs the oxygenation of blood flowing through the lungs. A bloodstream with a reduced oxygen saturation will consequently deliver a diminished oxygen supply to working muscles.
Training at a slightly lower oxygen saturation level (80-90%) can potentially increase the hypoxia-inducible factor, signaling the nuclei of the body’s muscle cells that a positive adaptation is needed to achieve a higher level of homeostasis. Increased levels of erythropoietin (a hormone which boosts red blood cell count) and brain-deprived neurotrophic factor (a protein that enhances brain function and increases blood flow to essentially all vital organs) are huge potential benefits of intermittent hypoxic training.
Hypoxic Training Has Been Shown to Benefit the Elderly
Loss of muscle (sarcopenia) with aging is a common concern for the increasingly older population of the U.S. However, Frontiers in Psychology notes that a recent study on hypoxic training with an elderly population showed that strength training at a lower intensity can stimulate adaptations that are generally only produced with high-intensity resistance training.
Hypoxic training can definitely benefit muscle tissues. For older men and women in the study, their body changes came from using a low-intensity workout level and lower-impact exercises combined with hypoxic training, rather than a higher-intensity workout.
Hypoxic Breathing Methods
According to Mile High Training, there is a technique called intermittent hypoxic breathing that requires no additional equipment. This breathing technique was made famous by Dutch athlete Wim Hof, also known as “The Iceman.” Intermittent hypoxic breathing uses hyperventilation, breath holding and exposure to a cold environment to achieve positive training benefits.
HYPOXiXTM is another intermittent hypoxic training method. It combines progressive exercise with progressive hypoxic breathing.
HYPOXiX combines core training, total body strength improvement and a breathing method called Breathography. This breathing method uses extended exhalations and escalating breath retention to achieve a lower oxygen saturation level similar to the lower-pressure environment used for altitude training.
The main difference between the two methods is that an exerciser using the Wim Hof method must hold his or her breath after hyperventilation. This technique lowers the blood’s carbon dioxide level, triggering an aggressive lowering of oxygen saturation in the blood while the exerciser performs exercises such as push-ups and squats.
By contrast, an exerciser using the HYPOXiX method performs breath retention during exhalations at a low-lung volume. This technique raises the blood’s carbon dioxide level and increases blood flow to muscles and the brain.
However, some exercisers have claimed to experience dizziness with the Wim Hof style of breathing during exercise due to the extreme low levels of carbon dioxide from the hyperventilation before holding the breath.
Ultimately, safety is important when an exerciser is voluntarily hyperventilating during a workout. More research will be needed to determine all of the potential performance enhancements and therapeutic benefits of intermittent hypoxic breathing during exercise as described by Optimus Medica.
About the Authors
Adrienne “AJ” Fisher, M.S., C.S.C.S., earned her bachelor of science and master of science in sports and health sciences from American Public University. She maintained a 4.0 GPA, which earned her an academic scholar award. Her capstone project, “Intermittent Hypoxia with Exercise, Voluntary Breathing, and Rest: Potential Benefits for Physical and Mental Performance, Injury Prevention, and Heart Rate Variability” is available online and was written under the guidance of Dr. Daniel Graetzer.
AJ serves on the University’s Sports and Health Sciences advisory board and is a personal trainer for high-profile celebrities in NYC, L.A., and London. She has also worked with clients such as Adidas, Reebok and Marvel in movies such as “Black Panther, Wakanda Forever.”
AJ combines her former career as a Broadway entertainer with her research in breath-work and hypoxic training in HYPOXiX fitness programming, which integrates breathing patterns that restore core strength and optimize the nervous system, body composition, and brain function.
Daniel G. Graetzer, Ph.D., received his B.S. from Colorado State University/Fort Collins, a M.A. from the University of North Carolina/Chapel Hill and a Ph.D. from the University of Utah/Salt Lake City. He has been a faculty member in the School of Health Sciences, Department of Sports and Health Sciences, since 2015. As a regular columnist in social media blogs, encyclopedias, and popular magazines, Dr. Graetzer greatly enjoys helping bridge communication gaps between recent breakthroughs in practical application of developing scientific theories and societal well-being.
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