WRITTEN BY: Sheri Colberg
Editor’s note: Sheri Colberg, PhD wrote “The Athlete’s Guide to Diabetes,” a comprehensive book full of tips + tricks for Type 1 athletes. Below is an excerpt from the guide that details ways to prevent lows, particularly during exercise by actually using exercise as a method to do so. Colberg includes anecdotes from athletes with diabetes from around the world.
Preventing lows during exercise with exercise itself
You may also be able to prevent, treat, or reverse your impending hypoglycemia during exercise by some novel means. All of these involve using the exaggerated release of glucose-raising hormones that you can get by doing an intense, near maximal, or maximal bout of activity. The following options are based on research and athlete experiences:
1. Ten-second maximal sprint
A short maximal sprint may counter a fall in blood glucose levels. This has been studied by having exercisers with Type 1 diabetes perform a 10-second cycling sprint either before or after 20 minutes of easy cycling. Done before, sprinting may keep blood glucose levels from falling for the 45 minutes after exercise; done afterward, it may prevent a decline for at least 2 hours. This technique may also help anytime during exercise. Although sprinting will have a limited affect if you have extremely high levels of insulin or a blunted hormonal response, it is still beneficial as a short-term means of raising your glucose levels or preventing them from falling as quickly. As Martin Berkeley of Cardiff, Wales, said, “I always do a 10-second sprint at the end end of a run. This definitely helps prevent hypos by releasing adrenaline. I can clearly see the effect on my continuous glucose monitor.”
*Pro-tip: If you are going low and cannot stop exercising, sprint as hard as you can for 10 to 30 seconds to induce a greater release of glucose-raising hormones. But if you a lot of insulin on board, this strategy will be less effective.
2. Intermittent sprints (or interval training)
You can even keep your blood glucose higher during exercise by interspersing 4-second sprints into an easier workout, which comes closer to replicating what happens when you do sports like soccer or tennis. Doing a 4-second sprint once every 2 minutes during 30 minutes of otherwise moderate cycling has been shown to keep glucose-raising hormones higher, which keeps your blood glucose from declining as much. This effect is the result of both greater glucose release (by the liver) and less glucose uptake during exercise and recovery. Exercisers also experience the same response when they do sprint training and high-intensity interval workouts. Watch out, though, because when the hormonal effects wear off, you may end up more likely to develop hypoglycemia because doing sprints uses up more muscle glycogen.
3. Exercise type + order of training
You may also be able to lower your risk of exercise-induced hypoglycemia (or even hyperglycemia) by varying the type or order of training that you are doing during a workout session, such as whether you choose to do aerobic or resistance training first. We know that blood glucose levels tend to fall more during moderate aerobic exercise and less afterward when compared with resistance workouts; this causes less of a decline during the activity and more overnight. If you are already planning to do both activities during the same workout, you can vary the order accordingly.
If you are on the low side with your blood glucose, do your resistance training first, then the aerobic training to keep your glucose higher throughout the first half of your workout. If you are starting out on the high side, begin with easy to moderate aerobic training first to drop your levels and follow that with the resistance work, during which your glucose will stay more stable or rise somewhat (depending on intensity). Fabian Tukacs of Austria has found this works for him, too. He usually goes to the gym and starts his workout with a blood glucose of 100 to 115 mg/dL (5.6 to 6.4 mmol/L). After his weight training, he always does 20 minutes of cardio training; he ends with his blood glucose stable at around 100 mg/dL (5.6 mmol/L).