The most common thing I discuss regarding diabetes is
The following should answer these questions and provide some insight into the relationship of diabetes and exercise.
Normally, insulin is released from the pancreas when the amount of sugar (glucose) in the blood increases, such as after eating. Insulin stimulates the liver and muscles to take in excess glucose. This results in a lowering of the blood sugar level.
When exercising, the body needs extra energy or fuel (in the form of glucose) for the exercising muscles. For short bursts of exercise, such as a quick sprint to catch the bus, the muscles and the liver can release stores of glucose for fuel. With continued moderate exercising, however, your muscles take up glucose at almost 20 times the normal rate. This lowers blood sugar levels.
But intense exercise can have the opposite effect and actually increase your blood glucose levels. This is especially true for many people with diabetes. The body recognizes intense exercise as a stress and releases stress hormones that tell your body to increase available blood sugar to fuel your muscles. If this happens to you, you may need a little bit of insulin after intense workouts.
For a variety of reasons, after exercise, people with diabetes may have an increase or a decrease in their blood sugar levels.
The latest findings show that exercise such as strength training has a profound impact on helping people manage their diabetes. In a recent study of Hispanic men and women, 16 weeks of strength training produced dramatic improvements in sugar control that are comparable to taking diabetes medication. Additionally, the study volunteers were stronger, gained muscle, lost body fat, had less depression, and felt much more self-confident.
In most cases, mild to moderate aerobic exercise or activity lowers elevated blood sugar levels. The amount of lowering depends on a number of individual variables including:
On average, half an hour of moderate aerobic exercise such as walking can lower blood sugar level about 50 points. It is important to recognize that a lowering of blood sugar does not happen in people who do not take medications or insulin, which cause a lowering effect, and whose blood sugars start and remain within the normal homeostatic range. Remember that non-diabetic persons who exercise in a normal blood sugar range will maintain that range effortlessly via the well-controlled output of liver glycogen, in most cases regardless of intensity or duration of exercise.
People on insulin at risk for hypoglycaemia can try balancing the blood glucose lowering effect of half an hour of exercise with 15 to 30 grams of carbohydrate. Testing blood sugar via use of a meter before and after exercise will help diabetics learn to pattern the effect of exercise and will assist in developing predictive strategies and management techniques to balance blood sugar.
In the normal physiologic (non-diabetic) state, insulin levels are instantly dropped by about 50 percent at the onset of activity. During moderate aerobic exercise, when glucose as a fuel is used in greater amounts overall to produce energy, glucose also enters cells via additional pathways other than insulin, hence the greater flux of glucose into cells despite lowered amounts of circulating insulin. Notice that some insulin is required during exercise to regulate blood sugar levels and metabolism. This explains why severely elevated blood sugars in type 1 diabetes (+300-400mg/dl) may not come down with exercise, particularly if there is an insulin deficiency such as a missed or skipped injection.
When people with type 1 diabetes are deprived of insulin for 12 to 48 hours and are ketotic, exercise can worsen both the hyperglycaemia and the metabolic imbalance (ketosis). In this situation, avoid exercise until both insulin and blood glucose levels are stabilized.
Anaerobic, high intensity, power types of exercise may actually cause an elevation in blood sugar levels during and immediately after exercise. This rise in blood sugar is a result of the role of liver glycogen and hormonal responses to this type of activity.
In an experiment measuring insulin and blood glucose levels in non-diabetic subjects in response to the 90 seconds of an all-out maximal effort during the Wingate Cycle speed test, insulin levels rose significantly to maintain appropriate blood glucose levels. In the person with type 1 diabetes, when insulin levels do not rise, intense anaerobic exercise can cause a significant elevation in blood sugar. If you work with clients who observe this response, you should be sure your clients are aware that corrections for elevations relative to exercise should always be conservative as metabolism and insulin sensitivity remains elevated. This places the diabetic athlete at significant risk for low blood sugar as a result of this increased effect of insulin. Remember too that metabolism stays elevated for hours after all types of exercise. This will increase insulin sensitivity as well and may place those with diabetes at higher risk for hypoglycaemia, potentially even during the night while sleeping.
Persons with diabetes should make a plan with their healthcare providers to prevent overnight blood sugar excursions, particularly after long duration or evening exercise. This may even involve middle-of-the-night blood sugar monitoring, additional carbohydrate in a pre-bedtime snack or both.
Provided exercise is controlled and prescribed by an informed qualified professional.
