Past 12 months, though reporting this write-up on the emerging craze of endurance athletes making use of constant glucose displays (CGMs), I attempted it myself for two months. The first write-up centered on the science (sparse while it is) powering promises that recognizing what your blood sugar is performing at any specified instant can help you gas additional proficiently and accomplish much better. But I figured it would be enjoyment to share some of my true CGM data—so what follows are 5 agent samples that illustrate some of my ordeals.
To help me interpret this information, I referred to as Kevin Sprouse, a sporting activities medicine medical doctor in Knoxville who also serves as head of medicine for the EF Training-Nippo professional biking workforce. Sprouse makes use of CGMs with his Tour de France cyclists (while not through competition), as well as with leisure athletes in biking and other sporting activities.
To begin, I emailed him some work out data—which, it turns out, is completely the completely wrong technique. “It’s definitely important to look at the 24-hour period around the work out,” he defined when we talked. “Looking at just the work out is a miscalculation. It is myopic.” Very low blood sugar through a work out might be the consequence of a poor supper the evening right before. High blood sugar might just suggest that you didn’t get plenty of snooze. Without the need of these contextual clues, the work out information by yourself will not explain to you a lot.
With that caveat, here’s some information, with glucose measurements on the still left axis and jogging pace (calculated with a Wahoo GPS enjoy) on the right axis:
March 28: Easy seven.five-Mile Operate
This was an straightforward operate with a mate at about eight:00/mile pace, and the information is quite normal of what I noticed in the 1st thirty day period or so of putting on a CGM. But there is a dilemma with the information. You can see the minute-by-minute updates when I’m eating my pre-operate banana. But as soon as the operate begins, I’m only receiving readings just about every 15 minutes. That’s due to the fact I still left my cellular phone powering, and the CGM itself only documents readings just about every 15 minutes, which are then uploaded to your cellular phone future time you connect. So this sample may be lacking some important fluctuations through the operate.
Supersapiens has since launched a committed wrist reader for persons like me who loathe jogging with their telephones. But as soon as I recognized the dilemma, I borrowed a pink narwhal fanny pack from my daughter and begun getting my cellular phone alongside.
April eight: Interval Work out
With my cellular phone in my pocket, I now see a lot additional motion in the information. This work out consisted of a 15-minute warm-up 4 sets of (approximately) one:00 tough, one:00 straightforward, three:00 tough, one:thirty straightforward 15-minute interesting-down. Throughout the tough portion of the work out, you can see my glucose concentrations climbing like a staircase.
This was appealing to me, due to the fact the simplistic way of wondering about a CGM is that it is a gas gauge, telling you how a lot juice you have acquired still left in the tank. That’s evidently not the case in this context: the tougher I go, the better my glucose climbs, producing a wonderful staircase sample. As my muscular tissues begin burning by way of gas additional speedily, excess power from reserve tanks like the carbohydrate saved in my liver is staying unveiled into the bloodstream to hold me sprinting.
Then, when I finish my intervals and begin jogging slowly and gradually house, my blood sugar remains sky-high (anything earlier mentioned a hundred and forty is viewed as unusually high) due to the fact I have ramped up my gas system but am no longer working as tough.
Those people readings of a hundred and seventy at the conclusion of my work out are undoubtedly high, but probably nothing to be concerned about, Sprouse suggests. A single fantastic signal: as quickly as the work out finishes, they fall quite speedily into a additional ordinary array. That probably suggests that my human body didn’t require to generate a spike of insulin to deliver my blood sugar again down. If I’d taken a gel or other gas through that work out (which I didn’t), Sprouse would have endorsed me not to hassle, as my glucose concentrations have been currently high plenty of.
Might 18: Zoom Presentation
On this unique working day, I gave an on the web presentation to a non-financial gain team. It was just 15 minutes prolonged, for a smaller and friendly viewers. But hey, I however get nervous. It was fascinating to see how everyday living functions, and mental condition additional usually, impacted my blood sugar concentrations. In the context of exercise, assume about the difference involving an straightforward operate, a tough work out, and an important race. Your pace is various, but so are your pressure concentrations. In the interval work out earlier mentioned, how a lot of that staircase outcome was responses (my muscular tissues require additional glucose) and how a lot was feedforward (my brain is on high notify, mobilizing bodily resources in anticipation of needs)?
It is also appealing to see the crash later on. I typically feel like a squeezed-out sponge after giving a speak here’s the physiological correlate. Levels below 70 are viewed as unusually reduced. How did I reply? Probably by eating something sweet, consequently the subsequent spike at around three P.M. (For the 1st thirty day period or so of putting on a CGM, I dutifully entered just about every food and snack into the Supersapiens app, but by this point the novelty experienced worn off and I was largely only recording pre-work out meals.)
Might 20: 42-Mile Bicycle Trip
I’m not a lot of a bicycle owner, but a single of the circumstances I needed to test with the CGM was an prolonged work out in which I might conceivably bonk. Would the emotion of hitting the wall in fact correspond with an unusually reduced blood sugar examining? It doesn’t often, Sprouse told me: “We’ve all considered we have been bonking and definitely we just weren’t quite suit.”
I organized to go for a 4-hour experience with a mate, largely at a comfortable pace. The exception was the 1st 20 minutes or so, when I rode tough due to the fact I was late for our meeting, and the past 50 percent hour, when I rode tough just for the heck of it. In this graph, the right-hand axis is my coronary heart price in its place of pace.
The all round image is approximately what you’d be expecting, Sprouse suggests. Glucose concentrations are rather secure through the main part of the experience, but steadily begin to edge downwards after about one.five to 2 several hours. I intentionally didn’t gas at all through this part of the experience, to see how reduced I’d go. When we eventually stopped for a quick break after around three several hours of riding, my glucose concentrations dipped all the way down below 70. Then I hit them with a gel and a Larabar, totaling 50 grams of carbs, and you can see my blood sugar instantaneously reply with a massive spike.
About 50 percent an hour after the gas surge, I split off from my mate and begun hammering house. A single unanswered concern is whether my blood sugar was likely to plunge pursuing the spike no issue what, or whether the plunge was precipitated in part by the truth that my muscular tissues out of the blue begun burning gas additional rapidly. My suspicion is that the main reduce is a response to the sugar-fueled spike—but then, with about ten minutes still left in the experience, I begun heading uphill for the last extend. At that point, you can see my coronary heart price spike, and the blood sugar concentrations briefly raise yet again, just as they did through the toughest areas of my interval work out.
Sprouse’s take, phrased additional politely, was that I’d fueled like an idiot for this experience: nothing at all for three several hours, and then mainlining a massive bolus of sugar. (He recognized, when I defined, that I was making an attempt to generate intense values with the CGM.) If I in fact needed to enhance efficiency, he mentioned, the graph suggested that I wouldn’t have necessary any gas for a experience like this lasting up to most likely two several hours. For the longer experience, I would reward from scaled-down, additional repeated doses of fuel—perhaps 50 percent a banana right here, a few sips of sporting activities consume there, and so on.
Might 23: seven-Mile Easy Operate
This was another Sunday early morning straightforward operate, quite comparable to the a single from March 28 apart from that I brought my cellular phone with me to get right information. But this time, my blood sugar concentrations are swinging around wildly. As with the bike experience, this was partly by layout. Generally I eat minor or nothing right before heading out for a early morning operate. This time, I experienced a peanut-butter-and-honey sandwich—because I understood it would mess with my blood sugar.
For as prolonged as I can remember, I have experienced something referred to as rebound hypoglycemia. If I eat something, significantly if it is carb-hefty, thirty to 60 minutes right before a early morning operate, then 15 minutes into the operate I’ll begin emotion light-weight-headed. It’ll past 5 to ten minutes, then vanish. What’s going on, I have collected, is that my breakfast or snack triggers a delayed insulin response that kicks in approximately when I’m setting up my operate. Both of those insulin and exercise are then making an attempt to decrease my blood sugar, and it overshoots right before receiving well balanced out.
I needed to see this in motion, consequently the sandwich. You can see that my concentrations are rising sharply right before I even begin jogging. Then after about ten minutes of jogging, they begin dropping. On this unique operate, I didn’t get the entire light-weight-headedness, but did feel quite sluggish for a though. Then the concentrations finally stabilize at a suitably elevated degree for the rest of the operate.
Sprouse’s tips for this predicament caught me off-guard: he suggested throwing in a brief dash. Just as through my interval work out (or even my on the web speak), ramping up the exertion and adrenaline will jolt your blood sugar upward. Apparently, he mentioned that through the Tour de France, he tells riders not to have a last pre-race food in the couple of several hours right before levels that begin with an uphill, since they may require to be completely ready to go tough right from the gun. For initially flat levels, which normally begin by noodling around carefully, they can go ahead with the excess food two to three several hours before—but then hold gels completely ready in case they require a increase early in the stage.
So what is the all round takeaway from all this? To be honest, I didn’t get a possibility to put the product by way of its right paces. This was mid-pandemic, when races have been canceled and my 4- and 6-12 months-olds have been both of those understanding from house. I experienced hassle slipping absent to coach for additional than 50 percent an hour at a time, and when I did I was not setting the planet on fireplace. You can see the blood sugar spikes from when I was waking up in the center of the evening and stressing about the condition of the planet.
Nonetheless, there are some glimmers of the CGM’s likely: for dialing in the fueling on prolonged rides, for figuring out how to avoid rebound hypoglycemia, and for observing the way my human body reacts to pressure. That mentioned, as Sprouse pointed out, you definitely require to zoom out from personal routines to see the 24-hour context, and the every day or weekly patterns. That’s a lot of information to sift by way of, and Supersapiens’ massive problem (which they’ve been chipping absent at since my demo operate ended in June) is to translate it into digestible and actionable advice—even for these of us who really don’t have a person like Sprouse on pace dial.
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