This process requires that we answer three questions:
- What is the product alleged to do?
- What is known?
- What conclusions/deductive leaps can reasonably be made?
What are elevation masks alleged to do?
(Per the manufacturer of a popular commercial device)
- Increase training intensity
- Provide the benefits of hypoxic training without having to ascend in altitude
- Improve breathing mechanics
- Improve exercise performance
- Promote “belly-breathing” which is suggestive of “diaphragmatic breathing”
- Strengthen the diaphragm
- Burn more calories in less time via increased training intensity
- Preferentially target the diaphragm and intercostals
- Mechanism of action is increased airway resistance
- Settings on the mask simulate different altitudes
What is known about high altitude physiology and training theory?
- Training intensity is not a subjective phenomenon but the degree of output relative to one’s maximal performance. By this definition sprinting maximally for five seconds is more intense than holding one’s breath for two minutes even though the latter might feel more difficult.
- Hypoxia is defined as a deficiency in tissue oxygenation
- Tissue hypoxia decreases maximal aerobic power
- Sufficiently high altitudes do not allow athletes to train at the kinds of intensities encountered in sea level competitions
- Exposure to altitude elicits physiological adaptations that improve the delivery and extraction of oxygen
- At altitude, hypobaria (low pressure) induces hypoxia while the relative percentage of oxygen remains unchanged
- Some hypoxic devices (e.g. “altitude tents”) decrease the relative percentage of oxygen at normal atmospheric pressure; normobaric hypoxia
- Exposure to normobaric hypoxia is inferior to hypobaric hypoxia for performance at altitude
- It can take 14+ hours/day for four or more consecutive weeks in a normobaric hypoxic tent to increase sea level aerobic performance in a clinically meaningful way despite statistically significant increases in red blood cell volume
- Current evidence suggests that the magnitude of improvement in sea level endurance performance doesn’t justify the practical and logistical burden of living at high altitudes and training at low altitudes
- Elevation training masks do not decrease the percentage of oxygen at sea level or decrease the overall atmospheric pressure; they resist the inhalation and/or exhalation phases of ventilation
- Elevation training masks have been shown to decrease oxygen saturation (SP02) during exercise
- Elevation training masks have not been shown to increase red blood cell volume
- These types of devices are effective in improving inspiratory muscle strength
- No studies have been conducted that investigate selective diaphragmatic and intercostal recruitment with these devices
- Belly breathing is not necessarily desirable or indicative of preferentially diaphragmatic breathing. More on this here.
- Ventilation is typically not a limiting factor during strenuous exercise in healthy subjects; enhancing this quality does not improve exercise performance
- The concept of diaphragmatic strength/weakness has not been extensively studied in athletes but more so in populations with neurological conditions
What reasonable conclusions can be drawn from the above?
- Both actual altitude and elevation masks decrease the intensity at which one can train during prolonged aerobic efforts
- Elevation training masks are a not substitute for high altitude; hypobaric hypoxia reigns supreme over any devices that attempt to simulate it
- Elevation training masks decrease oxygen saturation via a different mechanism than high altitude
- The duration for which the masks are typically worn is unlikely to incite lasting alterations in red blood cell production
- Elevation training masks are only likely to be beneficial to athletes during the rare situations in which it can be objectively determined that ventilation is a limiting factor in performance
- It’s always easy to evade responsibility for clinical decisions by waiting for more research on a particular topic. Here, however, many of the benefits attributed to elevation training masks don’t make theoretical sense in light of what we already understand about other phenomena.
- Eliciting presumably favorable physiological adaptations does not always improve performance. Fixating on physiology can confound performance. As it currently stands, VO2 max, lactate threshold, inspiratory muscle strength, hematocrit, minute ventilation, and the like are not competitive events. The first place finisher in the 10k at the Olympics did not have to give his/her gold medal to the person with the higher V02 max who didn’t qualify for the final heat. Physiology matters but there are already objective criteria in most sports that matter much more. Beware of products that celebrate abstract indicators without a single mention of actual performance.
- The endorsement of a professional athlete (even one who is unpaid by the manufacturer of a device) does not make a product any more or less useful