The challenge that most with Type 1 diabetes will report when asked about exercising, will be how to manage their blood glucose in response to exercise. Exercise increases the body’s sensitivity to insulin, and because of this low blood glucose can occur. Whether or not it will depend on a number of individual factors, and in order to be successful in managing your blood glucose you must consider all of them. Some of the factors you need to consider are:
Your blood glucose at the time you begin exercising – In a position statement from the American Diabetes Association, the authors recommend the target range for blood glucose prior to exercise be between 90-250 mg/dl. (1). This wide variation is because of the individual needs of those with diabetes. For more specifics on what your blood glucose should be, consult your health care physician.
The intensity of the exercise – low, moderate, and high-intensity exercises tend to lower your blood glucose, the rate at how quickly your blood glucose drops depends on the intensity. There is evidence that very high-intensity exercises (Sprinting and Powerlifting are good examples) can actually raise your blood glucose The recommendations are beyond the information provided here, but the link discussing this is included here.
The type of exercise – exercise tends to drop most for aerobic exercise, less for resistance exercise, and none for flexibility exercise. That should not discount the value of flexibility exercise. First, without flexibility exercises the aerobic and resistance exercises become difficult. Second, flexibility routines such as yoga or tai chi have an element of meditation, which can combat stress, a concern for those with diabetes.
The length of time you exercise – the general rule of thumb is that the longer you exercise, the greater the impact on your blood glucose. This can be a factor during activities, such as gardening or raking leaves.
The amount of insulin in your body - While exercise is being conducted (and sometimes after), insulin sensitivity will increase. Any type of insulin that is in the body is susceptible, regardless of whether it is a basal rate or bolus from an insulin pump, or short or long-acting insulin if you are on multiple daily injections. There are a few ways of managing this included below:
It is also important to note that Insulin sensitivity can occur during the activity and in some instances after the activity (sometimes as long as 24 hours after). The intensity and the length of time are the two strongest factors in the length of time that one is insulin sensitive.
In order to see how your blood glucose responds to exercise, the best recommendation is to monitor your blood glucose before, during, and after exercise. Remember that you are trying to determine patterns so that you are able to avoid low blood glucose, and the only way you can do that is repeated testing around exercise sessions. (This is a reason why you may want to consider a continuous glucose monitor, for its ability to give trending information.)
If your blood glucose is trending down prior to exercise, consider eating something prior to beginning the exercise session. Carbohydrate sports drinks are one suggestion, as well as glucose tablets, Lifesavers, or Skittles. Theses should also be readily available should you need them while you are exercising.
Blood glucose can also run high during exercise. It was previously mentioned that high-intensity exercises can cause blood glucose to rise, but so can sports endeavors where individuals are competitive. If your blood glucose is elevated (above 250mg/dl) check your blood or urine for ketones. If you test positive for ketones, avoid high intensity or stress-related activity.