Alex Brown

 

Diabetes and Exercise: Unspoken Knowledge

 

People with type 1 diabetes mellitus who seek advice about exercise from their healthcare provider are frustrated, confused, and consequently, may become resistant to exercise.  This enhances the stereotype that people with T1DM are reluctant to exercise and don’t want to improve their health, blood glucose management, or increase insulin sensitivity.  The gap between educating people with type 1 diabetes mellitus (T1DM) and exercise is closing at a slow rate, however, this could be much faster if healthcare professionals included the three energy systems into their diabetes education.  This paradigm shift in diabetes education could be the beginning of a new standard of care.

 

Energy Systems

Understanding the type of energy used and how the energy systems effect people with T1DM is highly critical for blood glucose levels and succeeding at any exercise.  During aerobic and anaerobic exercise, athletes can experience the three energy systems: immediate, lactic acid (glycolysis) and oxidative.  The main result that athletes want to have during performance is the ability to maximize production of adenosine triphosphate (ATP), which is found in muscle fibers and synthesized from macronutrients (carbohydrates, fats, proteins) (Antonio & Smith-Ryan 2013). 

Figure 2: Energy system interaction. Phosphagen (immediate), glycolytic (lactic-acid), mitochondrial respiration (oxidative). This graph illustrates approximately the duration and ATP output of each energy system. Source: Baker et al., (2010)

Immediate Energy System

For T1DM patients that perform in short and powerful events, the immediate energy system is used, and the system is fueled by intracellular, stored ATP and creatine phosphate (CP), which are both in muscle fiber, and are coupled together (ATP-CP).  Due to the limited amount of stored ATP and CP, the immediate system is utilized for the initial 10-15 seconds of exercise.  T1DM patients must understand that this energy system does not use glucose for performance, thereby blood glucose levels do not typically lower.  Blood glucose levels typically rise through the immediate energy system due to glucose-raising hormones (Colberg 2015).  In this energy system, people with T1DM may adjust their nutrition and insulin intake to prevent negative outcomes.

Latic Acid Energy System

            T1DM patients who perform in short and high-intensity exercises will utilize the lactic acid energy system between 10 seconds and 4 minutes.   The lactic acid system requires the use of glucose and stored glycogen to generate ATP.  During this energy system carbohydrates are consumed to activate the glycogenolytic enzyme to degrade glycogen thereby allowing available glucose to be used to produce ATP (Antonio & Smith-Ryan 2013).  In addition, skeletal muscle will intake glucose from the blood, if blood glucose is increasing.  When carbohydrates and glucose are the main fuel source, blood glucose levels typically rise for T1DM patients and will rarely lower unless exercise is prolonged (Riddell et al 2017).  When utilizing the lactic acid system, nutrition and insulin balance may be necessary to optimize performance.

Oxidative Energy System

T1DM patients who perform in lower intensity exercise such as walking, running, swimming, rowing, or cycling, and for longer than 5 minutes, they will use the oxidative energy system.  The rate of production for ATP is not as aggressive as the lactic acid system therefore ATP is generated oxidatively (Antonio & Smith-Ryan 2013).  The sources of fuel will come from two macronutrients and one periodic table element; carbohydrates (degraded to glucose), fat and oxygen.  Glucose is obtained from blood glucose, either from carbohydrates or the stored glycogen in the liver.  Fat is obtained from muscle fibers and the blood, which is from adipose tissue lipolysis (Antonio & Smith-Ryan 2013).  The main point for T1DM patients to understand when they are in the oxidative system is that this system uses blood glucose to produce ATP to sustain prolonged exercises (Figure 3).  Consequently, the patient’s blood glucose will lower from the utilization of glucose to make ATP and the amount of insulin circulating throughout the blood (Riddell et al 2017).  T1DM patients will need to adjust nutrition and insulin intake to avoid potential health hazards and optimize performance.  

Figure 3:  An illustration of the lactic acid and oxidative energy systems and how they produce ATP in the cell. Source: Antonio & Smith-Ryan (2013)

Next Steps

As more T1DM patients are becoming physically active, it is important that healthcare professionals are knowledgeable about blood glucose management strategies for athletic performance as well as “an understanding of the pathophysiology of diabetes and its nuances” (Horton & Subauste 2016).  Expanding the knowledge of healthcare providers could involve education training sessions or restructuring “continuous education credit” (CEC) courses so they are more equipped to successfully support their patients.

References

American Psychological Association (2010). Publication manual of the American Psychological Association (6th ed.). Washington, DC: Author.

Baker, J. S., McCormick, M. C., & Robergs, R. A. (2010). Interaction among Skeletal Muscle Metabolic Energy Systems during Intense Exercise. Journal of nutrition and metabolism, 2010, 1-13. https://doi.org/10.1155/2010/905612

Colberg, S. (2015). Exercise Engery Systems: A Primer.  Retrieved: http://www.diabetesincontrol.com/exercise-energy-systems-a-primer/

Horton, W. B., & Subauste, J. S. (2016). Care of the Athlete With Type 1 Diabetes Mellitus: A Clinical Review. International journal of endocrinology and metabolism, 14(2), e36091. doi:10.5812/ijem.36091

Riddell, M., Gallen, I., Smart, C., Taplin, C., Adolfsson, P., Lumb, A., Kowalski, A., Rabasa-Lhoret, R., McCrimmon, R., Hume, C., et al. (2017) Exercise management in type 1 diabetes: a consensus statement. Lancet Diabetes Endocrinol. 2017 Jan 23 Published online 2017 Jan 23. doi: 10.1016/S2213-8587(17)30014-1

Sheri R. Colberg, Ronald J. Sigal, Jane E. Yardley, Michael C. Riddell, David W.Dunstan, Paddy C. Dempsey, Edward S. Horton, Kristin Castorino, Deborah F. Tate; Physical Activity/Exercise and Diabetes: A Position Statement of the American Diabetes Association. Diabetes Care Nov 2016, 39 (11) 2065-2079; DOI: 10.2337/dc16-1728