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Preventing Hypoglycemia During and After Exercise

Mar 3, 2009

Last time Sheri Colberg, Ph.D., FACSM, gave us tips on how to deal with Exercise-Induced Hypoglycemia, this week she takes it a step further by teaching us how to Prevent Hypoglycemia During and After Exercise.

Preventing Hypoglycemia During and After Exercise


By Sheri Colberg, Ph.D., FACSM

SheriYou may be able to prevent, treat, or reverse your impending hypoglycemia during exercise by some novel means. Remember the hormonal effects of intense exercise discussed previously? Some researchers decided to study the effect of doing a short, maximal sprint to counter a fall in blood glucose levels. Some males with type 1 diabetes ate breakfast after injecting their usual insulin dose, waited until their blood glucose levels were no higher than 200 mg/dl (11.1 mmol/L), and then did 20 minutes of easy pedaling on a cycle ergometer. At the end of that, they immediately performed a 10-second cycling sprint. Interestingly, the sprint prevented a further decline in their blood glucose levels for at least 2 hours afterward (compared with when they didn’t do it). This technique works anytime during exercise. Although sprinting will have a limited effect if you have extremely high levels of insulin or a blunted hormonal response, it’s still beneficial as a short-term means of potentially raising your glucose levels. Whenever you start to feel low, sprint as hard as you can for 10 to 30 seconds to induce a greater release of glucose-raising hormones.

Along the same lines, another study by the same researchers confirmed that doing the same 10-second sprint, but this time immediately before doing 20 minutes of moderate-intensity cycling, also works to keep blood glucose levels from falling for the 45 minutes after exercise. Levels still fall similarly during 20 minutes of exercise, but the large increase in hormones elicited by the preworkout sprint apparently may keep them from dropping as much afterward.

You can even keep your blood sugars higher during exercise by interspersing 4-second sprints into an easier workout. When diabetic exercisers do a 4-second sprint once every 2 minutes during 30 minutes of otherwise moderate cycling, their glucose-raising hormones again stay higher and their blood sugars decline less. These effects are the result of both greater glucose release (by the liver) during exercise and less glucose uptake during exercise and recovery. 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.

After exercise, your main concern will be prevention of postexercise, late-onset hypoglycemia, which can occur both because your glycogen levels are low and being replenished (during which time your insulin action is higher) and because hormonal response to low blood sugars diminishes after exercise. Keep in mind two key points to prevent it. First, if you can start to restore your muscle glycogen right after exercise at the fastest rate possible by taking in adequate carbohydrate, you’ll be less likely to get as low later on. The period in the first 30 to 60 minutes after exercise is the critical time when your muscles can take up glucose without much need for insulin. Second, you may have more than one time following a workout when it feels as if your body is rapidly depleting your blood glucose. A recent study showed a biphasic increase in carbohydrate requirements—both right after exercise and again from 7 to 11 hours afterward. Be on the alert for this second wave of potential postexercise hypos and prevent them with adequate food intake and medication changes.

Another study suggested that when it comes to prevention of lows during and after exercise, not all drinks work equally well. Volunteers with type 1 diabetes took in water, whole milk, skim milk, sports drink A (carbohydrate and electrolytes), or sports drink B (carbohydrate, fat, and protein) before, during, and after an hour of moderate cycling in the late afternoon. The number of calories in the drinks averaged around 450, and no insulin adjustments were allowed beforehand. Interestingly, all the drinks except for whole milk and water spiked blood sugars above 200 mg/dl (11.1 mmol/L) during the time between the end of exercise and dinner. Sports drink B (with the extra protein and fat) caused persistently elevated blood glucose levels. Glucose declines after dinner were least in people who drank the whole milk. So, although carbohydrate is most important to replace in the short run, for longer prevention of lows, extra protein and fat intake may also help.

This column is excerpted from Diabetic Athlete’s Handbook (released November 2008 from Human Kinetics), which contains essential exercise-related information and examples for type 1 and type 2 diabetic exercisers. Look for it in stores or find links to places to buy it online on www.shericolberg.com, along with additional information.