Filed under: Altitude
Altitude affects what your body needs and how it responds, especially when it comes to exercise. Acute mountain sickness (AMS)—caused by dry air, a decrease in oxygen, and low barometric pressure—can severely impact your health and performance. The good news is there are things you can do to help reduce your risk of altitude sickness.
Performing physical activity—whether you’re at the gym or on a mission—at moderate (4,000–7,900 ft or 1,200–2,400 m) and high (7,900–13,000 ft or 2,400–4,000 m) altitudes can be challenging. At high altitude, oxygen pressure is significantly lower, which results in less oxygen in the blood and muscle tissues. And as altitude increases, there’s also a decrease in air temperature (about 2°F for every 500 ft or 150 m), less moisture (resulting in drier air), and increased solar radiation. AMS can affect anyone who is unacclimatized and ascends too rapidly to high altitudes. Symptoms can include headache, nausea, fatigue, dizziness, vomiting, sleep problems, shortness of breath, dehydration, and impaired cognition and balance.
The risk and severity of altitude sickness are greater above 4,000 meters, and treatment might require evacuation to lower altitude or immediate medical attention. To reduce your risk of AMS, wear sunscreen, drink water, and try to limit your physical activity at altitude for the first 24 hours. Acclimate to moderate elevations (2,000–3,000 m), if possible.
With current and future military operations in mountainous regions, the issue of AMS is a serious concern. However, leaders can help manage and perhaps prevent AMS among Warfighters by being aware of the elevation, types of activities, and lengths of stay at altitudes. Visit HPRC’s Altitude section to learn more about performance at altitude.
Can you train in the heat to improve your performance at altitude? The answer is “sort of.” “Cross acclimation” or “cross tolerance” is the idea that exposing yourself to one environmental condition can help you adapt to another one as long as they have certain things in common.
As it turns out, this is the case for heat and hypoxia (low oxygen). This is important because athletes and service members can be exposed to altitude without prior or sufficient acclimatization. Altitude sickness can cause several problems, especially decreased performance. But some evidence shows that this method of training in hot conditions to prepare for altitude can actually work.
If you climb to the top of a mountain, there’s less air and less pressure. And you’re getting less oxygen with each breath. This can be simulated at sea level (in special labs) where pressures are normal, but the amount of oxygen in the air is reduced (fake altitude).
However, there’s a bit of a catch. Training in the heat under artificial low-oxygen conditions—normobaric hypoxia or “fake altitude”—involves normal pressure, which is different from “real altitude” or hypobaric hypoxia, which involves reduced oxygen at low pressure. The difference is in the pressure.
So, do these two environments cause the same types of physiological changes? There are several other factors involved in real-altitude acclimatization that might not be accounted for at fake altitude, so the jury’s still out.
Training in the heat might prepare you for performance at altitude—to a point. Ideally, if you’re going to be at altitude, try to acclimatize yourself as much as you can.
The Altitude Readiness Management System (ARMS) app’s designed to predict how likely Soldiers are to experience acute mountain sickness and decreased physical performance at various altitudes. Using this new Android app (developed by the U.S Army Research Institute of Environmental Medicine), leaders can plan mountain missions around those likely to be impacted by sickness.
The ARMS app also provides an acclimatization module for planning strategic ascents and rests to minimize sickness. Altitude sickness can cause serious symptoms including nausea, fatigue, headaches, and weakness, affecting health and the mission itself too. While the app can’t prevent illness, it can help minimize the impact of mountain sickness, set appropriate expectations, and improve readiness and performance. The app has been fielded to the U.S. Army Forces Command (FORSCOM) and the U.S. Special Operations Command (SOCOM) only, but it might be available to the public soon.
Using your military Pro Mask or other commercial mask device as a method of respiratory muscle training (RMT) isn’t going to prepare you for higher elevations. Increasing the strength of your respiratory muscles which help you breathe—your diaphragm and the muscles between your ribs—will improve aerobic fitness, especially for long-duration tasks.
RMT can be achieved through whole-body aerobic exercise, upper-body strength conditioning, and some commercial RMT devices. Studies show that RMT slightly improves performance in those who are already aerobically fit (e.g., military personnel). It offers somewhat more benefit for those less fit or with chronic conditions.
Your Pro Mask was made to protect your lungs, eyes, and face from chemical and biological agents, radioactive particles, and battlefield contaminants. It doesn’t create enough airflow resistance to help improve aerobic capacity. In addition, it wasn’t designed as exercise equipment. There is no scientific evidence that suggests using commercial masks at normal altitudes will improve your performance at high altitudes. Read more about the U.S. Army Research Institute of Environmental Medicine’s (USARIEM) review of Pro Masks and commercial products for exercise training. Check out HPRC’s take on using high-altitude masks and improving work performance at higher elevations.