Every day, you have the choice to be physically active or not. This choice over time can influence how well you feel, the overall quality of your life, and how long you'll live. It is easy to be inactive in today’s sedentary world, but it is important to engage in daily physical activities to keep your joints flexible, your muscles strong, and your heart healthy.
Exercise offers many benefits to people with diabetes. It can increase energy levels, improve mood, and help keep blood sugar levels in a healthy range. It may strengthen muscle and improve bone density. It may improve coordination, balance, strength, and endurance. It can help to reduce the risk of colds, infectious diseases, cardiovascular disease, cancers, and additional chronic diseases. It can help you stay at a healthy weight, relieve anxiety and depression, and aid in stress-relief. It can even increase mental clarity, increase focus, and boost mood and self-confidence. Similar to foods, exercise can be thought of as "medicine". As exercise has so many benefits, people with diabetes should strive to be active any way they can.
But, what happens when you exercise with diabetes?
Exercise will generally have a blood glucose-lowering effect for individuals with diabetes and may help to improve insulin sensitivity for those who are still able to produce insulin as in type 2 diabetes.
However, blood glucose may react differently to different types of exercise and circumstances, especially depending on what medications are taken for the diabetes. Individuals who take insulin, sulfonylureas, and meglitinides have increased risk of low blood sugar when they exercise. Fear of low blood sugar is one of the biggest barriers to exercise.
Additionally, individuals on insulin are also at increased risk of high blood sugar after bouts of vigorous exercise. For individuals on insulin, a 30-minute run may cause blood sugar levels to decrease while other days that same run may cause blood sugars level to rise. Strange, right?
Well, it makes sense when you break down what happens in the body when you exercise…
When you exercise, your muscles require more energy. This prompts the body to release extra sugar, called glucose stored in the liver and in the muscles as glycogen. Glucose is vital to physical activity for all individuals – those with diabetes or not. Glucose is the building block of carbohydrates and is released by the body in order to fuel the muscles when more energy is needed. The muscles use glucose from recently consumed carbohydrates as well as from glycogen stores to fuel physical activity. The more glycogen the muscles store through carbohydrate intake prior to exercising, the longer the glycogen will last during physical activity. When glycogen is depleted after strenuous activity, muscles become fatigued.
The release of glucose during exercise can sometimes be a problem for individuals on insulin, if the body does not have enough insulin to use up that glucose properly by the muscles. If too much glucose is released during exercise and stays in the blood due to low insulin levels, blood sugar levels may rise. Additionally, stress hormones may be released during vigorous exercise which can increase blood sugar.
Not having enough insulin to use up the sugar in the blood can also cause the body to begin burning fat (stored fatty acids) for fuel. When the body starts to burn fat, toxic substances called ketones may be produced. This is one of the reasons that individuals with diabetes who are on insulin are recommended to check ketones and not exercise when blood sugar levels are elevated above 250 mg/dl. Individuals should stop exercising if ketones are present in their blood, because this can result in further dehydration and ketoacidosis, which is a medical emergency. Stopping physical activity and treating the high blood sugar according to your doctor’s recommendations can help you get back on track. Exercise will only burn more fat and produce more ketones.
Other days, blood sugar levels may dip during exercise. This is also caused by the body’s need for extra glucose. This happens when the body uses up all of the glucose that it has stored, so that there is no more to be released when the muscles need it. If you experience symptoms of low blood sugar during exercise, you should stop physical activity right away and treat your low accordingly using the 15-15 rule.
Low- to moderate-intensity exercise generally leads to a reduction in blood glucose levels resulting from increased glucose uptake by active muscles. While vigorous exercise may lead to an increase in blood glucose levels for individuals taking exogenous insulin.
Planning ahead and knowing your body’s typical blood glucose response to the specific exercises you do can help you prevent from going too low or too high. Take note of the way you feel and what your blood glucose level is before and after you exercise to assist with developing a plan for the next time you do it. Checking your blood sugar levels prior to exercising and every hour if exercising more than one hour, will help you confirm whether you need an extra snack to prevent low blood sugar. Adjusting your insulin dosage according to your doctor’s recommendations may also be helpful, especially when exercising consistently and on a schedule.
Don’t hesitate to take a break during your exercise routine if you feel that you need to eat a snack, drink some water, or go to the bathroom. You should take a break if you feel any signs that something is wrong. Keep others around you informed of your condition and bring plenty of snacks and water to keep you on track and in control.
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