The beneficial effects of exercise are clear. Individuals who perform even modest aerobic exercise have lower rates of heart disease. Resistance exercises help to maintain muscle mass, which increases the basal metabolic rate and may help to maintain body weight. In addition to the well known benefits of exercise, it is now clear that aerobic exercise improves insulin sensitivity. Glucose uptake by skeletal muscle is facilitated by exercise, which may increase the predictability of the insulin response. This increase in insulin sensitivity has been shown to last up to 24 hours. Thus, a daily routine of aerobic exercise will improve insulin sensitivity throughout the day, every day. It may result in improved overall glycemic control, a reduction in the hemoglobin A1c, and a reduction in the daily dose of insulin.
A word of caution about exercise:
First, the usual disclaimer that any exercise program should not be undertaken without the approval of the treating physician. In addition, patients with type 1 diabetes, especially females, are more prone to silent myocardial infarctions (heart attack). Thus, it is absolutely essential that an exercise program be under the supervision of a physician.
In addition, it is unwise for anyone to strain, performing the so called valsalva maneuver, while lifting heavy weights. In view of the small blood vessel disease associated with type 1 diabetes, I think that it is particularly inappropriate for patients with type 1 diabetes to do this. When lifting weights, be sure to breathe in and out regularly throughout the exercise.
Also, dehydration leads to insulin resistance. Thus, it is especially important for patients with diabetes to drink plenty of fluids while exercising.
Since exercise improves insulin sensitivity, the blood sugar may fall significantly during exercise. Blood glucose levels may need to be checked during exercise, and glucose tabs should always be available. We have seen the blood sugar fall from about 220mg% to about 110mg% with 1 hour of walking, a few glasses of water, and no supplemental insulin.