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During moderate exercise, your breathing rate increases to 40 to 60 breaths per minute, or about 25 gallons of air.
The lungs deliver oxygen to the bloodstream and exercise improves their efficiency.
Muscles demand more oxygen during exercise, and your heartbeat speeds up to meet the need.
Arteries move oxygen-rich blood to the muscles; veins return oxygen-poor blood to the lungs for a refill.
The Expert: Rich Rife
Rife is the lead explorer at Mountain Fitness Research, which prepares climbers to reach big summits.
Endurance requires fitness but also balance. Your lungs, heart, and muscles have to work in harmony to max out your potential and efficiency. As soon as one part goes out of whack—you’re working too hard, so your breathing rate increases, spiking your heart rate and draining power away from your legs—you’re doubled over, sucking wind. You need to train your body, sure, but also know how to read it.
A backpacker’s happy place is in the aerobic zone, where breathing is easy, heart rate is low, and muscle recovery is constant. But hills (and storms and looming nightfall) happen, spiking breathing and heart rates as the body tries to keep up with—and then recover from—anaerobic exertion. Best bet: Emphasize aerobic training (heart rate zones 1 and 2; see right). Rife suggests keeping 75 percent of your cardio workouts at a low enough intensity that you can do it while breathing through your nose exclusively (work harder—zones 3 and 4—the other 25 percent to build strength). To find a comfy pace on the trail, try the sing test: If you can’t carry a tune while you’re hiking, you’re going too fast.
How to Measure Your Heart Rate
Start with your max heart rate, which is 220–[your age]. Now break out that calculator to train and hike at the right intensity.
Zone 5: 90% max HR
Example Hiking up a 50% grade with a 40-lb. pack Sustainable for 1-5 minutes
Zone 4: 80-90% max HR
Example Hiking up a 30% grade with a 40-lb. pack Sustainable for 15-30 minutes
Zone 3: 70-80% max HR
Example Trekking up a 15% grade with a 40-lb. pack Sustainable for 1 hour
Zone 2: 60-70% max HR
Example Walking up a 15% grade with a daypack Sustainable for 1-2 hours
Zone 1: 50-60% max HR
Example Walking on the flats with a daypack Sustainable Until you get blisters
Common Cardio Problems
The Problem If your heart’s beating like crazy, your body’s in fight-or-flight mode, either from overexertion or from a particularly nervy section of trail.
The Fix If you notice a sharp spike, stop in a safe place and rest until your heart rate slows down to the normal range (50 percent of your max; see above right). Take deep, slow breaths to calm yourself down and decrease sympathetic nervous system activity (psyching yourself out ups your heart rate). Once things are under control, continue to keep your heart rate in the right zone by monitoring nose versus mouth breathing.
Shortness of Breath
The Problem Physical exertion wears on muscles, including your diaphragm, making it harder for your lungs to fill. You need more oxygen to counteract this, but due to high exertion, high altitude, or both, you can’t get it. The resulting CO buildup in the brain is a surefire path to lightheadedness, malaise, and other hypoxia woes.
The Fix Catch this early by paying attention to your breathing patterns. If you notice any shallowness or tension, stop for a moment and rest until your heart rate drops below about 110 beats per minute. Then, set a slower pace from there. If you’re at altitude already, you’ll need to do the same, but after descending until your symptoms subside—hiking down 500 to 1,000 feet should do it.
Am I Mountain Ready?
Prepping for a big challenge? Try this to see if you’re ready: Perform as many reps as you can of forward crunches, Russian twists, and supermans until you can do no more. Finish one exercise before moving to the next (don’t rest between) and record how many reps you did. Then, immediately, throw on a 30-pound pack and walk on an inclined treadmill for 30 minutes. Once done, complete the exercise circuit again in the same way. If your second effort isn’t at least 80 percent of the first, you’re not ready yet. Refocus your training on the exercise that drops the most.
Pro Tip: Listen to Your Body
Feeling your neck to check your pulse is possible, but will you actually do it? Invest in a cheap heart rate monitor, or use the one on your smart- or GPS watch. Instant biofeedback will help you stay in the right heart-rate zone, avoid going anaerobic, and keep your energy up longer.