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August 2003

Body Of A Backpacker

It's lean, it's mean, and it can last forever.

The Tests

Backpackers have serious heart

Galen Burrell marches to a different beat than most folks–a much slower beat. Burrell, who calls himself “naturally relaxed,” had an astoundingly low resting heart rate (RHR) of 42 beats per minute (bpm). While the other participants weren’t quite so slow thumping, the group’s average RHR was just 59 bpm, far better than the 72 bpm average of the general population.

Experts like Henderson and Holm say those slower heartbeats speak volumes. That’s because RHR is typically lower in athletes and is a good measure of fitness. “A low resting heart rate indicates that your heart is very efficient–it’s pumping more blood per beat,” says Holm.

Interestingly, the RHR test highlighted one factor that can mess with your ticker: altitude. A day after arriving in Boulder, Robinson’s pulse measured about 15 beats per minute higher in the lab than in his sea-level home in Mountain View, CA. Henderson was hardly surprised. “Your resting heart rate, especially initially, will be higher at altitude,” he says. That’s because at altitude, the oxygen-carrying capacity of your blood drops (see “Why Do We Bonk At 14,000 Feet?” on page 59).

Exercise is also known to lower blood pressure, and our backpackers scored well here, too. A reading of 120 over 80 or lower is considered optimal; our group averaged 119 over 76. “Overall, we found good numbers,” says Henderson. “Everyone’s values were in the healthy range.”

A bunch of hard workers

To hell with aging gracefully. By manhandling the big, bad VO2 max test, Buzz Burrell shows you can still be kicking *** when your coworkers are considering retirement. The 51-year-old put up numbers that amazed the BCSM crew.

The VO2 max test is many things. For one, it can be the longest 10 to 30 minutes of your life. Test subjects, outfitted with a nose plug and a mouthpiece, hit the treadmill. The pace and grade are slowly jacked up until the tester can’t continue. From a scientific point of view, all that suffering reveals exactly how much oxygen your body uses in a minute given your body weight. Put simply, it’s the gold standard of exercise tests because it measures your aerobic capacity for work-in other words, the size of your engine. About 80 percent of your VO2 max is written in your genes, says Henderson; the rest comes from training.

As a group, our backpackers produced excellent VO2 max values, with the men averaging 61 and the women 46-scores similar to what Henderson finds in other serious endurance athletes. (By comparison, a typical man in his 20s or 30s scores around 40, while the average woman performs in the low 30s.) Buzz was the team’s VO2 superstar, scoring a 64-an astonishing 200 percent of the results predicted by his age and weight. What makes the elder Burrell’s mark even more phenomenal, says Henderson, is that it is nearly identical to his son Galen’s VO2 max of 64.7, despite a 28-year age difference. VO2 max is known to fall with age, but Buzz’s result is proof that training can slow this decrease.

The group’s numbers also show that backpacking can increase your aerobic capacity without the need for lung-busting sprints, says Henderson. “These people aren’t doing lots of interval training, yet their VO2 max values are all exceptional-probably because they do a lot of high-volume training at a moderate intensity.”

Lean, mean, and hungry

No doubt about it, long days on the trail burn some serious calories, so it’s no surpise our testers are low-fat specimens. “It doesn’t sound like much, but if you need 3,000 calories per day just to maintain your weight, you’ll need 21,000 calories for a week,” says Henderson. “And that’s a lot of energy bars.”

To get the skinny on just how lean our athletes are, Henderson and Knutson measured both body mass index (BMI), which analyzes the ratio between your height and weight, and body fat percentage, using a skin fold caliper test that measures the thickness of the subcutaneous fat layer at seven places on the body. “For the latter test, 10 to 12 percent body fat is an ideal level for guys,” says Henderson. “For women, closer to 18 percent is best for sustained endurance.” The men in the group averaged 9.8 percent body fat, the women 17.3 percent.

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