It's no secret that Continuous Glucose Monitors (CGMs) are creeping into the athletic world, but how do we use them to affect performance? After training with CGMs for two months, here are my takeaways for both health and performance.
I was fortunate enough to get my hands on the elusive Supersapiens CGM & software for two months. During this time, I trained and prepared for UCI XC races, the National Championships, and a World Cup; analyzing my daily responses to diet along the way. The whole process was extremely simple and user-friendly, where I received minute-by-minute updates at my fingertips.
This product, in my opinion, is going to be a true game changer at every level; for the amateur athlete looking to improve their diet to the world tour pro aiming to optimize their fueling.
After nearly 60 days with a CGM, I’m still learning about my glucose from both a health and performance perspective. Here are my biggest takeaways from this experience.
Off-hours Glucose:
The target of off-hours (or non-training) glucose control was to keep a more stable glucose pattern. When we’re not training, minimizing big spikes and time above 140mg/dL can be more beneficial for our long-term health. Without getting too into the weeds, that essentially keeps us from constantly needing insulin to swoop in and help us. With that in mind, I would implement a few practices to minimize those higher exposures.
Meal layering:
In this case, I refer to “meal layering” as the order to which you eat your food. What I found was that by simply eating fibrous and protein-rich foods before my carbohydrates, I would really dull down the glucose response. So, typically I’d have a salad and/or my meat staple first, then move on to the rice, pasta, etc.
The Walk:
It’s quite remarkable what a post-meal walk can do I’m sure you’ve heard this before, but walking just ~10min after a meal can drastically impact the glucose response. As we talked about earlier, exercising muscles opens another door to pulling glucose into the cells. Even a short stroll after eating would steady out glucose spikes and keep me from getting big swings in blood sugar response.
As a comparison, I’ve shown here two different meal experiences. The first is a Chipotle burrito while traveling and the second was pancakes with a post-meal walk (which is arguably a bigger glucose bump…)
I began to feel weird if I didn’t do a post-meal walk after dinner. I made this a staple –mostly for breakfast and dinner– to manage big swings in glucose and assist in “loading” glucose if I had a carb-heavy meal.
Staying Above the Line:
The “line”, as I call it, is what Supersapiens considers below 70mg/dL. Supposedly, a lot of time below it can impair recovery, glucose storage, and impact day-to-day training. While everyone has their own range, significant drops or time below the “line” can certainly impact how well my body resynthesizes, stores, and prepares glucose as it’s limiting the amount readily available.
Prime: Preparing for the Work
The period leading up to a big workout, event, race, etc. is the “priming” phase. This is, realistically, the 3-4 days leading up to an event – not the classical “carbo load” night before.
My goal would be to increase total glucose exposure, or the running average blood glucose times (x) the hours in the day, by ~5mg/dL for a couple of days leading up to an event. This short-term increase in blood sugar would help me ensure there was more glucose available to stay topped up and primed for the event. This is not the time to hold back or skimp on fueling where I’d come in with less-than-optimal muscle glycogen.
Timing can be crucial. One big takeaway was the prevalence of a phenomenon called “rebound hypoglycemia”. This is the overcompensation of pulling glucose levels down due to the combination of insulin response and muscle demand. For a physiology lesson, your body can pull glucose into the cells through either insulin production or passively through exercising muscle; like a second doorway.
This experience can increase when you get out to train within that 30min - 90min period following a meal because both are happening simultaneously. When I ate and then hopped on the bike immediately, this would be almost nonexistent. Yet, a little delay and you can be feeling the classic, rough low blood sugar symptoms. If you can’t wait or are training early, some ways to avoid this include fueling more just as you get on the bike or just prior to hopping on,
Perform: On the Bike Fueling
Go time! Whether it was a hard workout, a long ride, or a race day, I tried to utilize the Supersapiens as much as possible. The biggest takeaways for on-the-bike training?
- I have been under-fueling more than I think.
- Fueling consistently, but in smaller servings, helped me to maintain both consistent and higher levels of glucose.
- Starting with more “real” food on endurance rides benefited glucose management throughout.
- If you take a gel, be ready to back it up.
First off, I have been *likely* under-fueling for a significant amount of my rides. I may have been fine just “getting by” for some of them, but does that necessarily make it right? More fuel could have led to more training stimulus, which could have led to a little more gain over time.
For me, taking smaller doses of food (like half a bar) but more consistently led to a smoother glucose profile during the rides. Also, I noticed that, during endurance rides, starting out with more complex, real food in the first hour or two helped manage the glucose control the whole ride. I’d start with a homemade snack, banana, or great bars like Maurten SOLID and Skratch Anytime Bars. Then, I'd transition into simpler fuel. Keeping a great hydration mix with me along the way, like Skratch Lab's.
Lastly, if you start using gels and chews (quick energy) be ready to back it up with more. These fuel sources are amazing for lighting a fire when you have a race and/or hard workout…but if you are popping them then make sure you have enough. I took a gel with about 30-45min left in one of my endurance rides, thinking I’d be back home soon and it’d be fine. This spiked my glucose about 15min later and then dropped like a rock in the final few miles.
While this is entirely my personal experience, I do feel there are some valuable points of interest for any athlete or health enthusiast out there. Fortunately, The Feed is an amazing place for testing out various modes, methods, and products for fueling and make things extremely easy. Plug and play with your fueling plan to see what works for you!
Disclaimer: The information, including but not limited to, text, graphics, images and other material contained on this article are for informational purposes only. No material on this site is intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment and before undertaking a new health care regimen!
