A Real-Time Fuel Gauge for Endurance Athletes


Ahead of very last year’s Earth Half Marathon Championships in Gdynia, Poland, a young British length runner named Jake Smith experienced a get in touch with with experts from a compact corporation his agent experienced related him with. They’d crunched the details from his performance two months before at the London Marathon, where by he’d struggled in his assigned function as a pacer, and experienced a straightforward concept for him: “They basically claimed, ‘You have to have to eat additional,’” he remembers.

On the again of his higher proper arm, the 22-12 months-outdated was putting on a circular adhesive patch about an inch throughout, with a tiny filament embedded into his flesh. It was a continuous glucose check, or CGM—a device intended to keep track of true-time blood sugar (also acknowledged as glucose) concentrations in diabetics, repurposed for athletes by an Atlanta-based commence-up identified as Supersapiens in collaboration with the clinical device big Abbott Laboratories. The details Smith uploaded following London confirmed that his glucose concentrations experienced begun at a middling level and then declined steadily throughout the race. “By about 10 or 11 miles, I was like, ‘This should not sense like this,’” he claims. So in Poland on the day just before the race, he chowed down on pasta, rice, rooster, greens, and fruit, and he held a cautious eye on the Supersapiens application on his phone. Whenever his concentrations begun to dip, he ate additional.

The next early morning, following a breakfast of two bagels with Nutella, Biscoff unfold, and peanut butter, he took on the world’s greatest length runners. His time of 1:00:31 was a large personal greatest, smashing his own British underneath-23 record and very good for 18th place over-all. And his glucose levels—well, no one particular is aware of, since they were being so large that they maxed out the sensor in the course of the race. “They claimed they would like to know,” Smith claims, “but the application just wouldn’t go any larger.”

In late 2019, I received a LinkedIn concept from a dude named Brian Davis who desired to meet for coffee and tell me about a corporation he and his associates were being launching. The pitch, he instructed me following I’d signed the requisite NDA, was “the world’s initial human gasoline gauge.” The system runs on glucose, he spelled out, and a CGM would give athletes true-time insight in how effectively fueled they were being and when and what they must eat.

Davis was in Toronto, where by I stay, to meet with a York College researcher named Michael Riddell, who is amid the world’s foremost authorities on how men and women with diabetes reply to exercise. Diabetes is basically a difficulty with glucose manage, thanks to the absence or ineffectiveness of insulin, the body’s most important tool for shunting glucose out of the blood and into your muscle or fat cells. The enhancement and refinement of CGMs above the previous decade has experienced a massive affect on the skill of men and women with diabetes to hold their glucose concentrations inside of a protected variety. In individual, they’ve been critical for Group Novo Nordisk, a pro biking team whose customers all have Type 1 diabetes—not just for the health and safety of the riders, but also for their performance. That was the insight that led Phil Southerland, co-founder of the biking team, to launch Supersapiens in 2019. Soon after all, he figured, athletes with diabetes are not the only types who be concerned about bonking.

The idea of sticking CGMs on nutritious men and women is not totally unprecedented. In fact, when I wrote about blood sugar concentrations in stamina athletes again in 2017, the podcaster and physician Peter Attia praised his CGM as “one of the most insightful inputs I have experienced in my existence.” But Supersapiens faced a pair of sizeable road blocks to their target of advertising to athletes. Just one was regulatory: in most destinations about the world, you have to have a prescription to get a CGM. When I satisfied with Davis in 2019, they were being hoping to get approval for non-prescription gross sales by mid-2020. Supersapiens ended up launching in Europe very last fall, but remains unavailable in the United States. Many thanks in portion to COVID-associated delays at the Food items and Drug Administration, it in all probability won’t be accepted right until next 12 months.

The other obstacle—which is, if just about anything, even knottier—is that the url among blood sugar and performance is definitely complicated. We’re not like autos, which merely run on gasoline right until the tank is empty. Rather, our muscular tissues run on a elaborate mix of fuels—not just fat and carbohydrate, but different forms of fat and carbohydrate (of which glucose is just one particular) saved in different destinations (of which the bloodstream is also just one particular), in a mix that depends on the intensity and length of the process and the relative level of the different gasoline tanks. And if glucose concentrations are complicated in men and women with diabetes, buffeted by pressure and exhaustion and hydration and dozens of other things, they are even additional complicated in non-diabetics thanks to the motion of insulin. Just since you have very low blood sugar, in other text, that doesn’t imply you are about to bonk. And conversely, just since you have large blood sugar, that doesn’t imply you won’t bonk.

However, Supersapiens’ pitch is that some facts is better than none. Perhaps the heartiest endorsement of this pitch arrived in June, when the Union Cycliste Internationale, cycling’s around the world governing system, banned the use of glucose displays in competition—a ban that at the moment applies almost solely to Supersapiens, and implicitly assumes that recognizing your glucose concentrations offers you a aggressive edge. “The lovers don’t want to see Formulation Just one in bicycle racing,” UCI improvements manager Mick Rogers instructed Biking Weekly. “They want surprises. They want unpredictability.”

In the meantime, Supersapiens has signed partnership discounts with Earth Tour biking teams which includes Canyon-SRAM and Ineos (who can even now use the CGMs in education) and the triathlon team BMC-Vifit, and will be the title sponsor for this year’s Ironman Earth Championships in Hawaii, where by they are even now allowed in levels of competition. They’ve also enrolled additional than 400 pro athlete ambassadors, which includes luminaries like Kenyan marathoner Eliud Kipchoge, all of whom are uploading their details to the corporation for investigation. “Glucose concentrations in non-diabetics? We’re all a little unfamiliar with that,” admits Riddell, who is now a scientific advisor to the corporation. Elite-level education and racing adds another twist that will make this details trove contrary to just about anything beforehand analyzed, he claims: “Sometimes it’s large other situations, it’s quite very low. It is not abnormal, but it’s excessive.”

To observers like Trent Stellingwerff, a greatly respected sporting activities scientist at the Canadian Activity Institute Pacific with individual skills in sporting activities nutrition and metabolic rate, the biggest problem for Supersapiens will be extracting actionable tips from this firehose of details. To that conclude, the corporation has lately hired 10 additional whole-time experts, bringing its science team to twelve out of a total headcount of above 70. People scientists are receiving tantalizing glimpses of, say, the moment-by-moment ebb and movement of glucose in Kipchoge’s bloodstream throughout this spring’s Hamburg Marathon. But can that details tell Kipchoge just about anything about what he must do otherwise next time? “I’m sure the device measures properly,” Stellingwerff claims. “But my most important concern is: Why?

You’ve only received about a teaspoon of sugar in your bloodstream, and your system is meticulously engineered to hold it that way. Take in a triple scoop of ice cream, and your pancreas will release insulin to stash the excess sugar into your muscle and fat cells. Get chased by a lion, and pressure hormones will set off a surge of glucose from the liver into your bloodstream to give your muscular tissues the brief gasoline they have to have to fight or flee. For the duration of exercise, your muscular tissues burn up by means of glucose a hundred situations more rapidly than they do at rest, but the fragile equilibrium among source and need primarily retains concentrations in your bloodstream inside of a tight variety among about 70 and a hundred and forty milligrams per deciliter. That is why you just cannot merely presume that very low glucose concentrations imply you are working out of gasoline.

The crucial sources of electricity for stamina are carbs and fat, just about every of which can be saved in the muscular tissues themselves or in the bloodstream. Here’s a graph, from a the latest assessment in Character Rate of metabolism, that displays the gasoline mixture at diverse exercise intensities. Muscle glycogen and muscle triglycerides are carbohydrate and fat, respectively, saved in the muscle plasma FFA (no cost fatty acids) and plasma glucose are fat and carbohydrate, respectively, circulating in the bloodstream.

Chart of fuel mixture at different exercise intensities
(Picture: Character Rate of metabolism)

At the least expensive intensity, equal to an quick wander, fat presents approximately all of the gasoline. At the best intensity, equal to a brisk run, you are burning primarily carbohydrate, but predominantly in the form of muscle glycogen relatively than glucose. Wanting at a graph like this, you could question why everyone would treatment about glucose concentrations.

But if you remain on the bicycle or out on the trails for prolonged more than enough, the photo gradually modifications. You can only store more than enough glycogen in your muscular tissues to gasoline hard exercise for someplace about ninety to one hundred twenty minutes. As individuals provides dwindle, you get started to rely additional on glucose. Here’s another graph, based on scientific tests by College of Texas researcher Edward Coyle and other people throughout the nineteen seventies and eighties, demonstrating how the gasoline mix shifts throughout prolonged exercise:

Chart of how the fuel mix shifts during prolonged exercise
(Picture: Global Journal of Athletics Drugs)

Soon after three or four several hours, you are burning forty p.c glucose—or at the very least, you are if you can hold your glucose concentrations large more than enough with sporting activities beverages, gels, and other sources. If you just drink h2o, your glucose concentrations will drop, and performance will experience. This is the observation, laid out by Coyle in a 1983 paper, that underlies the whole sporting activities drink marketplace.

Gatorade’s concept is blunt: drink as significantly sporting activities drink as you can so that, God forbid, your glucose concentrations will never drop. Supersapiens has a additional nuanced concept: drink or eat only as significantly as you have to have. Soon after all, downing gels or beverages on the run prices time and typically leads to an upset belly or worse. We just about every have an optimal performance zone, neither as well very low nor as well large, which we can find by demo and error. “Below 110, I struggle to do extended rides,” claims Southerland. “At a hundred and forty to one hundred eighty I sense greatest. But these concentrations are incredibly personalised.” Smith’s zone seems to be additional like a straight line, considering the fact that he ran his breakthrough 50 percent-marathon almost completely above 200 mg/dL, the higher threshold for the application. Kipchoge’s details remains private, but Todd Furneaux, the company’s president, is eager to discuss in basic terms: “All of our incredibly elite athletes, when they are working, even in an Ironman, they are in the one hundred eighty to 200 variety. They are flatlining.”

The sensor that Abbott makes for Supersapiens is identified as the Libre Perception, and it’s billed as a “glucose activity biosensor.” In most respects, it appears to be to be similar to the FreeStyle Libre 2 CGM marketed to men and women with diabetes, but there are a couple of crucial tweaks. The activity variation sends moment-by-moment updates to the application (or to a forthcoming wrist show) through Bluetooth, in contrast to a 15-moment interval in the normal design. And the measurement variety is capped at 200 mg/dL, significantly lessen than what you’d have to have to securely check your concentrations with diabetes—presumably an endeavor to reassure regulators that it won’t be utilised as a clinical device. The products at the moment provide for sixty five euros (roughly $77), and just about every device lasts for fourteen days when you apply it to your arm.

The fact that athletes like Smith are blowing the higher limit absent is one particular indicator that the true-world details from athletes is not quite what the corporation expected. “Initially, we thought it was all about how to keep away from a bonk,” Furneaux claims. That idea may perhaps even now have merit: in a the latest research that gathered CGM details throughout exercise from men and women with out diabetes, Riddell notes that some men and women dropped effectively under 70 mg/dL, a variety he claims is associated with crystal clear impairment of cognitive and physical function. Wearing a CGM could have warned these men and women that they essential additional gasoline, foremost to better performance, nevertheless this declare has not been examined.

It is not crystal clear no matter whether the identical observation applies to elite athletes, nevertheless. Louise Burke, an exercise nutrition researcher at Australian Catholic College who has labored carefully with Australia’s Olympic teams for four decades, has viewed athletes drop under fifty mg/dL with no obvious sick outcomes, when other people present crystal clear signs at about seventy five. “It may perhaps rely on the caliber of athlete,” she claims. “Really elite athletes from time to time feel to be capable to press lessen. But generally we just don’t know.”

It is not just about the bonk, nevertheless. Burke ran a research before this 12 months with fourteen elite Australian racewalkers to take a look at no matter whether CGMs could pick up warning signs of chronic very low electricity availability, which is linked to health challenges and overtraining. The myriad things that make glucose concentrations bounce up and down throughout the day make it hard to attract meaningful conclusions, but Burke figures that the right away concentrations when you are sleeping could give a clearer signal of no matter whether you are receiving more than enough calories to gasoline your education. The effects haven’t yet been analyzed, so for now Burke is intrigued but unconvinced. “I’m not indicating it’s not heading to be practical,” she claims, “but I’m just indicating it desires validation.”

Yet another probability is applying the CGM to good-tune your carbohydrate loading just before a significant race, like Jake Smith, the British 50 percent-marathoner, did. Modern-day protocols normally contain a pair of days of incredibly large carbohydrate intake to make sure that your muscular tissues are totally stocked with glycogen at the commence line. But the concentrate on of eight to twelve grams a day of carbohydrate per kilogram of system excess weight works out to about sixteen cups of cooked pasta for a 150-pound athlete, which is no quick feat. You just cannot use a CGM to straight evaluate your glycogen shops, but the Supersapiens application offers you a trailing 24-hour glucose common. That amount could convert out to be a proxy for muscle glycogen shops, Furneaux claims, since if it’s larger than ordinary, it suggests the surplus glucose has nowhere else to go.

The very last couple of several hours just before a workout or race can also be difficult. In as a lot of as thirty p.c of stamina athletes, a phenomenon identified as rebound hypoglycemia will cause non permanent feelings of light-headedness and weak point following a couple of minutes of exercise. The obvious perpetrator: consuming straightforward carbs thirty to sixty minutes just before exercise, which triggers a increase in insulin concentrations that lingers for an hour or two. When you commence training, you then have two diverse levers—insulin and exercise—trying to lessen your glucose concentrations at the identical time, producing them to drop as well quickly. “We see this a lot in the Supersapiens details,” Riddell claims. “People are not fueling properly.” Just one countermeasure is to eat only in the very last five to 10 minutes just before exercise, so your insulin concentrations don’t have time to increase. But putting on a CGM also offers you the possibility of figuring out specifically how your glucose concentrations reply to diverse types of foodstuff and diverse pre-workout timings.

Plenty of novel and interesting likely uses? Examine. But what about real proof that sticking one particular of these points on your arm will make you more rapidly? Abbott’s website for the Libre Perception guarantees that it will “inform athletes about how to gasoline properly, to fill their glycogen shops prior to a race and to know when to replenish throughout a race to preserve athletic performance.” Adhere to the relevant footnotes, and one particular leads to a relatively generic 2015 assessment about the importance of refueling following exercise, when the other leads to a 2016 Swedish undergraduate thesis in which four countrywide-course swimmers wore a CGM for a week, with no intervention or performance measures.

Of training course, the revealed literature from time to time lags behind elite practice. I emailed Armand Bettonviel, the Dutch sporting activities nutritionist who was credited with assisting revive Kenenisa Bekele’s marathon career, to get his choose. Bettonviel is at the moment applying Supersapiens with Eliud Kipchoge and three other NN Functioning Group athletes, but the initial thing he emphasized was that decoding details from the CGM is “not yet hard science.” He’s applying it to build up a additional details-driven photo of the different techniques that Kipchoge’s system makes and uses glucose, and how they alter underneath diverse circumstances. People basic insights then let him to drill down into the specifics of Kipchoge’s in-race consuming protocol, which was meticulously optimized throughout his sub-two-hour marathon tries.

There are caveats, nevertheless. Bettonviel would like to ascertain Kipchoge’s “optimal blood glucose variety,” and determine out the greatest pre-race and in-race fueling protocol to hold him there. But any very good stamina athlete also desires to be capable to burn up fat efficiently: “I also strongly believe that that metabolic adaptability could be a crucial performance indicator,” Bettonviel claims. “All modifications made based on blood glucose values could perhaps have an effect on this adaptability.” Moreover, he’s obtaining that what is genuine for Kipchoge’s glucose responses is not always genuine for the other athletes, making it tricky to formulate basic guidelines. “Our team is even now discovering and analyzing,” he claims. “We don’t bounce to conclusions yet and any modifications made are compact types.”

Of the exceedingly scant details in the revealed literature on athletes putting on CGMs, almost all of it focuses on health relatively than performance. Most notably, another Swedish research revealed before this 12 months in Cell Rate of metabolism experienced 15 countrywide-team stamina athletes put on a CGM for up to two months. When compared to non-athlete controls, they expended additional time under the ordinary glucose threshold of about 70 mg/dL, primarily in the center of the night and they also expended additional time above the higher threshold of about a hundred and forty mg/dL, primarily throughout the early afternoon. For the duration of their education periods, on the other hand, they normally stayed inside of the ordinary variety.

The idea of nutritious, non-diabetic men and women applying CGMs to even more improve their health is in fact having a second. But it’s not with out controversy. When Supersapiens introduced its title sponsorship with the Ironman Earth Championships this spring, Tom Hughes, a clinical health care provider and sporting activities science lecturer at Leeds Beckett College in Britain, sounded a notice of caution. “I don’t believe I have viewed any proof that blood glucose drops noticeably throughout an Ironman,” he says—a declare that he’s examined on himself at the very least five situations, taking outdated-university finger-prick readings of blood glucose when he felt he was bonking and observing concentrations effectively above a hundred mg/dL. And he also is not convinced that obsessively tracking the peaks and valleys of your glucose readout throughout the day will tell you just about anything practical about your health. Rather, he claims, it’s merely an opportunity to “stress about another amount we don’t recognize.”

To my surprise, even Riddell, the diabetes researcher and Supersapiens scientific advisor, admits some sympathy for this point of view. “The obsession with quantities is truly worth producing about,” he claims. “Even amid men and women with diabetes, the affected person is typically the one particular who doesn’t want the CGM.” Soon after all, you now have a stream of non-end details that appears to be to be judging you, typically negatively, following each individual meal and snack. And when you test to “fix” your habits, your glucose concentrations don’t always reply in the way you assume. Riddell and his colleagues have recognized at the very least forty, and maybe as a lot of as 200, diverse things that influence glucose, making it difficult to type out which signals definitely make any difference. If the device is heading to catch on as an athletic aid, he claims, Supersapiens “needs to be better at the ‘so what?’”

That is less difficult claimed than carried out, but it’s why the company’s twelve experts are poring by means of the details from their athlete ambassadors, searching for styles and trends and telltale signals—and maybe even new science. Already the details is yielding a transformed understanding of what glucose seems to be like in major athletes. The traditional watch is that glucose values remain in the ordinary variety even throughout hard education, as viewed in the Swedish research. No one particular expected the sky-large values that Jake Smith and other people deliver throughout levels of competition. “Medical textbooks say ‘glucose homeostasis is unperturbed by exercise in non-diabetics,’” claims Riddell. “That’s incorrect! We know that! So it’s fifty decades out the window. We’re heading to rewrite the textbook.”