Exercise with Diabetes

Safe and effective exercise is different for people with diabetes than for the general population, beginning with the need to test your blood glucose before, during and after exercise. Dependent upon the type of diabetes you have, and how you are managing your diabetes, different exercise routines can have different effects on your glucose levels.  

When it comes to Diabetes, not all exercise is the same, and some exercise can even cause your diabetes condition to worsen.  

At Fitscript, we have identified some key information that can help you understand why you may or may not be having success with exercise and your diabetes.  If you want to begin having success with exercise and diabetes, it is very important that you understand the different variables that can effect glucose levels during exercise.

What are safe glucose levels for exercise?

First and most importantly, you must check your blood glucose before beginning any exercise or activity. Depending on your blood glucose level, you may start exercising immediately, or you may have to postpone exercise until your blood glucose levels are in an acceptable range.  Each person is unique and may have different personal experiences with blood glucose levels.

Generally, people with Type 1 diabetes, and people with Type 2 diabetes taking inject-able insulin, should be very careful for dropping glucose levels during exercise, and be sure to understand how and why the presence of insulin, and the other variables explained on Fitscript, cause glucose levels to drop.

For people taking oral medication only, the risk of low blood glucose during exercise is less, however pre-caution should still always be taken, especially if taking oral medication that increases insulin sensitivity.

Remember, always test your blood glucose before, during, and after exercise!

Lower than 100 mg/dL (5.6 mmol/L). Your blood glucose may be too low to exercise safely. Eat a small carbohydrate-containing snack, such as fruit, juice, or a granola bar, before you begin your workout.

100 to 250 mg/dL (5.6 to 13.9 mmol/L). You’re good to go. For most people, this is a safe pre-exercise blood glucose range.

250 mg/dL (13.9 mmol/L) or higher. This is a caution zone.To make sure it’s safe to exercise, you should test your urine for ketones. Excess ketones indicate that your body doesn’t have enough insulin to control your blood sugar. If you exercise when you have a high level of ketones,you risk ketoacidosis— a serious complication of diabetes that needs immediate treatment. Instead, wait to exercise until your urine ketones test kit indicates a low level of ketones in your urine.

300 mg/dl (16.7 mmol/L) or higher.  Caution!  Your blood glucose levels may be to high, it may be unsafe to exercise.   Consult with your physician or health care provider about strategies for exercise at these elevated ranges.

What role does insulin play?

Understanding what Insulin is, how different types of Insulin i.e. fast acting vs. slow acting effect glucose levels, and how different type of diabetes medication effect glucose levels while exercising is extremely important. There are literally hundreds of different types of insulin and medications on the market, each having its own unique effect.

In general, the following guidelines should be kept in mind when considering the effect of insulin, insulin resistance, medication adjustments and timing as relates to exercise.  Always consult with your physician or health care provider regarding your insulin, oral medications, and any other hormonal or medication related questions.  

What is Insulin: Insulin is a hormone, produced by the pancreas, which is central to regulatingcarbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen inside these tissues. Insulin stops the use of fat as an energy source by inhibiting the release of glucagon.

*Most diabetics understand the relationship between Insulin and carbohydrates, however do not realize that Insulin also affects fat metabolism. In fact, the presence of Insulin prevents the body from using fat as energy source!

What is the best time of day to exercise?

Morning Dawn Phenomenon: Some diabetics experience high glucose levels in the morning, also known as the morning dawn effect.   This is due to normal metabolic processes that have nothing to do with your diabetes. A healthy and functioning metabolism will produce energy (in the form of glucose) early in the morning in response to waking up and beginning to work. Another factor in high glucose levels early in the morning relates to other hormones that your body produces at night time, including cortisol.

Mid-morning: Many diabetics experience hypoglycemia in the mid-morning if the Insulin is peaking and their metabolism is not producing energy/glucose, or they have not eaten. Many diabetics experience the chasing insulin phenomenon in the mid-morning. This can be amplified if exercise or activity takes place while the insulin is peaking and or takes place on an empty stomach.

Afternoon: Personal Experience and the time of last Insulin adjustment/medication supplementation play the largest role in predicting how glucose levels will be affected in the afternoon. Some diabetics experience highs (hyperglycemia) after lunch, while others, if over medicated or having taken too much insulin, will experience lows.
Evening: Personal experience dictates the effect of glucose levels and exercise in the evening. You may go low or high at night during sleep due to normal metabolic regeneration and glycogen replenishment not being in sync with your insulin regiment and exercise schedule. This is a very common occurrence and can sometimes be very dangerous, with some diabetics’ experiencing hypoglycemic induced seizures in their sleep. It is very important to understand the natural rhythm of your metabolism and how sleep is used by the body to replenish the muscles with glycogen.

How does heart rate affect my glucose?

Using your heart rate as a guide is one of the best ways to train and is also one of the best indicators of potential blood glucose changes.   It is equally important and useful to keep track of and understand your perceived exertion level.  In many ways, your perceived exertion level is more indicative of potential changes in glucose levels.

In general, your body will catabolize a ratio of fat, carbohydrate, and protein during exercise and activity.  Different heart rate zones cause different ratio’s of energy catabolism, changing the primary source of energy, and correspondingly changing the presence of glucose in your blood.  Dependent upon the primary source of energy, and the presence of Insulin, your blood glucose levels may go down or up during exercise.

Remember, everyone is unique, and certain medication (such a beta-blockers) can effect your ability to raise your heart rate.  It is important to understand how heart rate zones affect glucose levels in the context of the other variables explained on Fitscript.com

How does activity affect my diabetes?

All of the skeletal muscles in your body consist of primarily three different muscle fiber types: Slow Twitch, Intermediate Twitch, and Fast Twitch muscle fibers. Depending upon the fiber type used during an activity, glucose levels will be affected differently, as requirements for energy metabolism change depending upon the fiber type and composition of the particular muscles you are using to achieve your fitness goal.