It could be rightly argued that you simply don’t need sophisticated physiological tests to achieve your athletic goals. Roger Bannister didn’t know how much salt he had in his sweat when he ran the world’s first sub-4-minute mile in 1954. California ultra-distance runner Zach Bitter, on the other hand, who in 2013 set the world record for the farthest distance ever run in 12 hours at 101.66 miles, knows exactly how many calories he’s burning at a 7-minute pace, and what percentage of that comes from fat.
Physiological tests are becoming more affordable, scientifically rigid and specialized for the citizen athlete. But what can a few tests tell you that you don’t already intuitively know? If you knew more precisely about how your body works, could you change up your training or alter your diet and run a better marathon? I got pricked, prodded and pushed in order to find out.
At the headquarters of Skratch Labs in Boulder, Colo., famed sports scientist Allen Lim straps a patch of pilocarpine to my forearm to test the sodium content of my sweat. This drug, induced into my pores by a 9-volt battery, forces a small area of my skin to begin to sweat at a rate somewhere between a lactate threshold and race-pace running effort.
At some point, every long distance runner has to consider their electrolyte needs. To ignore this is to court catastrophe, and leaving it to luck will eventually ruin a race that was important to you. As runners, our customary way of knowing who needs more salt was simply who had the nastiest sweat streaks on their clothes after a race.
“You primarily lose sodium in your sweat, and although people make a big deal of other electrolytes, it’s the salt that has the greatest performance and physiological consequences,” says Lim, co-author of “The Feed Zone Cookbook” and “The Feed Zone Table,” and sports science consultant to numerous elite endurance athletes. Sweat, however, is not the same across individuals. “I’ve seen people as low as 400 milligrams to 2,000mg of sodium per liter of sweat,” he says. “That’s like a shoe salesman carrying sizes 4 to 200.”
Lim has the rare ability to explain complicated science to anyone, a skill honed over years in the trenches of the Tour de France. The company he subsequently founded, Skratch Labs, makes electrolyte drink mixes that favor whole food ingredients. The suitcase-sized device he’s using to test me was originally designed to screen newborns for cystic fibrosis. Babies who have inherited the disorder have very salty sweat, around 3,500mg per liter.
After 20 minutes he removes the armband and extracts my sweat. As it turns out I’m average, at 864mg per liter. “Tour de France athletes are in the 700s; normal people are around 1,000,” Lim says. And this jibes with what I’ve figured out through trial and error over more than a decade of endurance racing.
Lim stresses that this isn’t about constantly making calculations or trying to be an athlete-chemist. Those at either end of the spectrum should pay closer attention to what they ingest during long training sessions and races, but it’s less critical for someone like me. “We want people to know basically if they are low, medium or high salt sweaters,” Lim says. “And you are right in the middle.”
Hormones are coursing through your body right now. Traveling through your veins, these hidden little chemical messengers coordinate complex processes like cell growth, metabolism and fertility.
Your lifestyle and habits affect these hormone levels, usually in small ways over time. When you’re training too hard and taking inadequate rest, your body sees this as a threat to your survival. So it downgrades resources to things like reproductive health because it has more pressing issues. Men might suffer a precipitous drop in testosterone, their virility hormone, and women could stop having menstrual periods (a condition called amenorrhea).
On one level it’s a form of overtraining-induced birth control, but the danger is that if an athlete spends too much time in this state, injury and burnout are inevitable. Since we don’t have any insight into our hormone levels, we’re left to our own perception, and, honestly, we’re terrible at this.
The only way to look under the hood is by getting your blood tested for hormone levels. Blood extraction is easy enough, but the challenge has always been having someone who knows athletes analyze your results and tell you in plain English what they mean. New internet services hope to bridge that gap.
I signed up with one such company, InsideTracker, to see what I could learn about myself. I then went to a nondescript blood draw location in a strip mall close to my house. Five minutes and five tubes of blood later, I’m done. It was surprisingly painless and quick. Three days later, an email arrives—the results are ready.
There is one big surprise: My testosterone group was low. The test showed that although I have enough free testosterone, too much of it is bound by sex hormone-binding globulin (SHBG), a protein produced primarily in the liver. When SHBG is high, it binds the testosterone and prevents it from being active. InsideTracker has videos to explain every
reading and hormone in detail, as well as a prescribed course of action, which I follow for the next three months the best I can—honestly, I fail about 20 percent of the time.
Now, three months later I’ve tightened up my diet and have more energy for life. My
follow-up test shows I’ve lowered my SHBG by 17 nmol per milliliter, but it hasn’t moved the overall number on my testosterone group. My vitamin D levels, which were in the perfect green zone on the first test, at 43 ng per milliliter, are now in the orange warning zone. This is likely because I take vitamin D3 supplements in the winter. This lifted my result to 53 ng, which InsideTracker flagged as borderline high, but most experts agree that toxic levels only begin closer to 150 ng.
I’ve got some work to do before my next test in three months and this time I’m committed to 100 percent compliance. I can’t help but reflect on how a service like this would have saved me entire seasons of discontent and dysfunction when racing was my focus.
Thankfully, the intensely unpleasant VO2Max test, the one where you run as hard as possible on a treadmill with that horrible breathing mask on, is fading from popular use by sports scientists. “It just doesn’t tell you anything useful,” says University of Colorado physiologist Jared Berg as he straps that same breathing mask on my face. Instead, he describes the protocol for the metabolic test he’s about to put me through. It sounds nominally more pleasant.
The goal is to find out how I use fat and carbohydrate substrates as fuel during various heart rate zones and running paces. The mask has tubes running out of it that attach to his computer next to the treadmill. I feel trapped and suffocated. Berg has me run increasingly harder and faster in 3-minute segments. He pricks my finger to record blood lactate levels between each increase. As I begin to run my sixth stage, at just over a 6-minute mile, my allergy to sustained anaerobic efforts flares, and I bail out. Berg assures me we got enough data, then disappears to crunch the numbers.
“You’re a stereotypical ultrarunner,” Berg says when he returns, explaining with charts and diagrams the complex science of my body. I understand about 40 percent of what he says.
I do get some solid, actionable takeaways: I learn how many calories I burn at each heart rate zone, and what percentage of that is coming from fat and carbohydrate. In my detrained state, my crossover point—the pace at which I go from metabolizing mostly fat as fuel to mostly carbohydrates—is a 7-minute mile and a heart rate of 155.
The data show that my optimum fat-burning zone is below 140 beats per minute, and this lines up perfectly with Phil Maffetone’s method of base training that I’ve been using as my governor this winter. It’s important to have optimal fat utilization in order to rely less on internal glycogen or external carbohydrate consumption during exercise. This, and the rate at which my lactate production overwhelms my ability to remove it, point to my need for a solid base training phase. And since fat oxidation is an aerobic process, Berg suggests 80 percent of my training time be spent in training heart rate zone 2, or below 140, to continue to improve fat utilization.
What Gets Measured Gets Managed
None of these tests are necessary—or inexpensive—and you can perform well without them. But having more information is always a good thing, and it allows us to make better, more informed decisions. Over years of trial and error some of this information might become apparent, but why not allow science
to shorten the learning curve?
There is the risk of “paralysis by analysis,” of course, but going into a season or a race armed with personalized knowledge of your body is empowering. Just knowing seemed to be enough to nudge my behavior in the right direction. And as technology improves, it seems prudent to use it to your advantage. Your competition surely will.