Exercise precautions diabetic heart patients

Exercise & Its Positive Implications on Glycemic Control in Type II Diabetes

Many with type I diabetes have a very difficult time controlling their blood sugars. For most diabetics, most of the time, the “rules” work. ” The rules being “If I do this, or do not do that, I can expect this result.” But there are many individuals for whom the rules do not appear to apply to them. Control may be elusive and they simply react to blood sugars swinging from highs to lows. When these diabetics attempt to practicing tight control they find their blood glucose level “over-reacts” to minute changes in diet, exercise, and/or insulin. They can  experience unpredictable rises and drops in blood glucose, within very short periods, as the result of very small changes. Small changes “break” their control, and they are thus said to be “brittle.”

The medical community stresses  the importance of exercise for all and especially for diabetics as they have a stronger likelihood of developing heart disease. Exercise is thought to reduce the risk of heart disease by keeping the arteries flexible, and diabetes has a tendency to harden the arteries. Yet for diabetics exercise carries risk.

I have frequently  had patients develop severely low blood sugars with exercise even though  when tested it was adequate prior to activity and they had eaten a decent meal. Some patients have been severely low – as in blood sugars 28-32 range. To an untrained eye it might have gone unnoticed. Often the sign in which I would pick up the emergent low sugar was the patient had more perspiration than usual or a vacant look in their eye.  Angina can occur if the blood sugar is low. If you are a heart patient and experiencing angina when exercising, stop and check you blood sugar.

An additional  challenge for many insulin dependant diabetics who are trying to lose weight through exercise  and nutrition is they have to eat a certain amount to maintain their blood sugar for exercise, and end up consuming more calories than the exercise session burns. When this occurs the advice is see a diabetic educator or health care practitioner to adjust medications.

I have also argued with many a patient who has blood sugars in the 400’s and wants to exercise, as they know the exercise will lower their sugars. However it is dangerous to the body to exercise strenuously when the blood sugar is elevated above 240’s or if there are ketones present. Ketones in diabetes usually indicate that you don’t have enough insulin. As a result, your body can’t use glucose for fuel, so it starts to burn fat, and that forms ketones. The presence of ketones in someone with type 1 diabetes shows a dangerous lack of insulin and the immediate need for more insulin. Exercise, at this time, will only burn more fat and produce more ketones. If ketones build up in the blood, it can lead to a serious condition called diabetic ketoacidosis (DKA), which requires immediate medical treatment. Exercising when you have ketones may make the situation worse and also put you at risk for DKA.  Ketoacidosis then increases the likelihood of heart attack, and arrhythmia. If you want to exercise, check your blood glucose. If your glucose is above 240 mg/dl, check for ketones. If ketones are present do not exercise until blood sugar is down, try again later in the day.

To begin an exercise program when one has poor control of blood sugar there are several safety issues to consider.

Guidelines for exercise for type 1 diabetes include:

  • If blood sugar is low (less than 100), it is necessary to eat  a minimum of 15 grams of carbohydrates and  preferably a protein which helps to hold blood sugar up for longer periods of time. Consider a snack such as a granola bar or cheese and crackers, a glass of milk. Plan on needing an additional 15 grams of carbohydrate for every 30-60 minutes of planned activity. Very active exercise may require more carbs. Many diabetics who work out strenuously will have to have a small snack midway through the activity to maintain the blood sugar in a safe range.
  • If blood sugar is over 240, test for ketones. If ketones are negative, exercise is permissible and encouraged.
  • Test blood sugar every 30-60 minutes during exercise.
  •  If blood sugar is between 100-200, take an extra 15 grams of carbohydrate for every 30-60 minutes of planned activity. Very active exercise may require more carbs.
  • If blood sugar is over 200, it is not necessary to have a snack unless exercising for 1 hour or more.

Testing  blood sugar after exercise will give varied results.

Often, a higher than normal blood sugar is seen right after exercise. Generally, exercise will lower your blood sugar. If the post- exercise blood sugar reading is unexpectedly high, you may need to consider if your blood sugar dropped so low during the activity that your body re-regulated itself by releasing counter-regulatory hormones. These can cause a  rebound and thus a high blood sugar reading.

Other considerations might be overestimating the impact of the exercise, engaging in a stressful kind of exercise (such as weight lifting) and eating too much carbohydrate beforehand. The blood sugar may drop in 30-60 minutes after the activity. This is a normal pattern due to hormonal changes and other factors. If taking an insulin dose shortly after intense exercise, less insulin may be needed. If correcting a blood sugar after intense exercise, correct blood sugar to a 200 target.

Often 6-12 hours after prolonged activity, the blood sugar may decrease. When starting a new exercise plan, or more activity is done, insulin doses may need to be lowered. It is advised to check blood sugar values  frequently and consider checking in the middle of the night if you have found very low levels in the early mornings.

 Do not take insulin to cover exercise-related snacks or snacks used to prevent or treat a low blood sugar!

Here are some points to keep in mind:

  • People who work out or are physically active on a daily basis may need to lower the total daily dose of their insulin.
  • For people who exercise more sporadically, the acute effect of exercise on insulin sensitivity may last hours to half-a-day and may require the insulin dose to be lowered just around the time of the exercise.
  • Unusually prolonged or vigorous activity may result in a decrease in insulin dose requirements, overnight and even into the next day.

If you have concerns or struggle with exercise consider joining a medically supervised exercise program run by exercise physiologists. Many hospitals have these within their cardiac rehabilitation programs. Benefits include – increased safety, use of their blood sugar monitoring equipment, reporting results and communicating with healthcare practitioners and better control of your blood sugars.


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