Optimizing Female Performance at Altitude

How to work with your female physiology to succeed in thin air.

If you’ve ever run, biked, hiked, or skied in the U.S. Rockies, European Alps, the Himalayans, or anywhere high above sea level—especially above 2400 meters or 8000 feet—you know performance drops as the air thins. That’s because oxygen levels are lower at high altitudes, so your cardiorespiratory system has to work harder to deliver oxygen to your working muscles than it does at sea level.

Your menstrual phase and/or hormonal status also impact your response to altitude. Research shows that premenopausal women who aren’t on hormonal contraception have a higher hypoxic ventilatory response at exercise (HVRe), which is the ability to increase breathing to help meet your oxygen needs during their early luteal/mid-luteal phase than in the early follicular phase. On the surface, that sounds like a positive, but it’s important to bear in mind that women’s respiratory rates are already elevated during this high hormone phase, so women may be more predisposed to asthmatic issues and higher respiratory distress. Postmenopausal women have similar HVRe as premenopausal women, though hypoxic cardiac response at exercise (HCRe), which is your cardiovascular system’s ability to increase output, is lower post-menopause, likely due to age-related changes.

No matter your hormonal status or age, your body can adapt to these challenging conditions. When you spend time at high altitudes, your body makes more red blood cells to carry oxygen, and those blood cells become more efficient at delivering that oxygen to your tissues. At the same time, your cells’ energy-producing mitochondria multiply to take in as much oxygen as possible.

Interestingly, women acclimate a bit differently than men. In a study of 16 women traveling from sea level to Pikes Peak, Colorado, which sits at about 4300 meters or 14,100 feet, researchers found that after acclimation, the women burned fewer carbs and more fat for exercise fuel. Alternatively, research shows their male counterparts tend to use more carbs for fuel at high altitudes. Since women have more body fat and are better fat burners at altitude than men, they might be better suited for exercise at high elevations. That said, higher intensity exercise may be harder for women in these conditions because estrogen triggers the body to spare carbs (which are needed for hard efforts), and progesterone increases breathing rates (which are already increased at high altitude).

Altitude Acclimation Strategies

What’s a lowlander to do if she has a big event or mountain adventure planned? Ideally, get out there early—like really early. Fourteen to 21 days is ideal. Obviously, that’s not realistic for most of us. Research (on men) has found that six days of partial acclimation can help, but again, that’s a lot of time and expense most women don’t have. Many women will opt to try to go out just two to three days ahead of time, but research finds no performance benefit to such a short period of time and in some cases, you may end up feeling worse before you feel better after three days.

If you’re in a position where you have to hit the ground running at high altitudes, you’re at risk for developing altitude sickness, which can happen when you exercise at high altitudes when you’re not adapted. Mild forms cause headache, fatigue, and lack of appetite. You can avoid going into the red at altitude by recalibrating your heart rate zones for high altitude (figuring that at about 6500 feet or about 2000 meters, your heart rate will increase about 10 percent over your sea level rate) and using those adjusted values during your event.

You can also help prepare your body for the challenges of altitude by performing heat acclimatization training ahead of time. Heat training adaptation increases your total blood volume, so you have more water and red cells in your blood to deliver more oxygen when you get to altitude. Your body’s vasomotor system also adapts by allowing your blood vessels to vasodilate more readily so you can carry more blood during exercise. Females and males respond equally well to heat adaptation training, but research shows that females need to do about twice as many heat acclimatization sessions (9, as opposed to 5) to get the same magnitude of adaptations as their male peers.

To do it, head to a hot place like a dry sauna or hot tub for up to 30 minutes after a workout or at the end of the day when you’re a little dehydrated. Afterwards, SLOW rehydration (over the course of 4-5 hours) is critical for adaptations. The combination of low blood volume (from the dehydration of exercise or passive dehydration from daily life) and thermal stress triggers a cascade of physiological reactions that help your body cope with heat stress (and altitude). For the best results, do it for nine days in a row, about two weeks out from your event. Then give yourself about 5 days to allow your body to rebound back to full blood volume before your event.

Your body will respond differently to heat training depending upon your hormonal phase. In the low hormone phase, which is right before, during, and right after your period, your body needs a 15 to 20-minute “primer” of heat exposure before the full session. So go into the sauna and heat up. Then get out for 5 to 10 minutes before starting your actual session. For women in peri and post menopause, this primer is also needed because of a slower response to the heat. If you're in the high hormone phase, your body has already shifted to a higher thermoregulatory threshold, and no primer is needed.

No sauna or spa available? Don’t sweat it. Hit six to eight 90-min hot vinyasa yoga classes over a 14-day period and reap the benefits of heat adaptation. 

Altitude Performance Strategies

Once you’re on the ground at your destination, these strategies can help you feel and perform your best during your high-altitude event.

• Stay hydrated. Ever notice that you pee more at high altitude? Increased urinary output is a very common response to being at altitude, as your kidney’s sense low levels of oxygen and kick into high gear, releasing erythropoietin (EPO), which triggers your body to produce more red blood cells so you can carry more oxygen. They also prompt you to pee more to decrease your blood plasma and make your blood thicker and hemoglobin more concentrated. That’s a productive process, but you don’t want to tip into dehydration. Increasing your fluid intake by about a liter a day will help you stay hydrated as you acclimate and help increase that ever-so-important plasma volume. Avoid plain water; you need some salt in your fluid! Instead sip on a functional hydration beverage (~7g sugar with 190 mg sodium per 8oz) and increase your intake of watery foods.
• Eat more carbs. Though research shows you burn more fat, especially in the high hormone phase due to estrogen and progesterone’s effects on sparing carbohydrate; you still need more carbs when you’re exercising at altitude. When at altitude, the body uses less exogenous carbohydrate (carbs you eat!) as a fuel during exercise, and relies more on liver glycogen; regardless of menstrual cycle phase. Eating a higher amount of total dietary carbohydrate helps keep your metabolism kicking for intensity. The additional carbon dioxide that carbs produce kicks up your breathing response and notch and helps prevent altitude sickness.  
• Open your vessels. Some athletes say they have success with using beetroot juice before events at altitude, which can help blood vessels relax and widen, but also know research on women is lacking here. 
• Avoid alcohol. Skip the chardonnay and/or IPA. Alcohol is a dehydrating diuretic, and it depresses the normal breathing response to high altitude. Overall, alcohol increases the risk of altitude sickness and can exacerbate symptoms.