Optimal Blood Glucose Levels for Sports Performance with Diabetes
What are the Optimal Blood Glucose Levels for Sports Performance When Living With Diabetes?
People with diabetes, frequently athletes, will ask me what the optimal blood sugar is to enable them to perform their best in sport and exercise.
I typically respond with the question “where do you feel the best”?
Most people will respond within the lines of what we hear as optimal glucose targets ranging from 70-180 mg/dL. Some will say they feel best a bit below the 180 mg/dl and others report a bit higher is fine for them. Personally, I prefer to individualize targets after discussing what the person has tried, what they experience in shift of glucose during exercise and what is safe. A person must be aware of how they feel/symptoms and what performance is like based on where blood sugar is sitting. Often in exercise how you feel may be related to your level of effort but with diabetes it could be related to glucose levels. Understanding where your performance peaks along with the glucose level at that time can help optimize your strategy for fuel/medication and exercise planning.
This is especially important to reach your greatest potential as an athlete. Using myself as an example in my sport (Cheerleading): I found that anything above 150 mg/dl is when I would start to get a bit of a “lag”. My body started to feel heavier when tumbling and each movement was a more fatiguing. Through my own experimentation, I felt I could perform the best making my target glucose on competition or game days 80 mg/dl – 140 mg/dl.
The strategy that I utilize follows the 2017 consensus published in The Lancet. This states the appropriate blood glucose at the start of exercise should be tailored to the individual with a reasonable starting range for most individuals doing aerobic exercise (or cardio-based) for about an hour in duration. The target is ~126–180 mg/dL(Riddell et al., 2017). This points out, the lower end is closer to 126 mg/dL (higher than I target for the lower end of target) to lower the risk of hypoglycemia and that the higher target may need to be considered depending on the individual. All those living with diabetes understand that maintaining blood glucose during sport and exercise can be a challenge. Sheri Colberg agrees with the 2017 consensus statement that 126-180 mg/dL is a reasonable target but takes it a bit further using information gathered in a survey. She states, “An ideal or optimal blood glucose target during most physical activities may be in the range of 108 to 144 mg/dL” (Colberg, 2019). Most of the athletes surveyed for The Athlete’s Guide to Diabetes (2019) said they aim for a glucose range of 80 to 180 mg/dL with a few of them aiming for lower or higher range, and most having a narrower target. (Colberg, 2019).
When glucose concentrations are too high because of insulin omission, perceived exercise or work effort often increases (as well as the risk of ketosis). Clinical experience and data from a field study in adolescents suggest that maintenance of a concentration of about 108–144 mg/dL, like Sheri said, might be ideal (Riddell et al., 2017). Another study examined athletes’ sports skills daily (Tuesday through Friday) by each subject at varying time points throughout the day. All 41 participants were tested while in an acceptable glycemic range and only some of the subjects were tested while hypoglycemic or hyperglycemic. The mean capillary blood glucose concentration during hypoglycemic testing was about 56 mg/dL, during the acceptable glycemic range was 157 ± 48 mg/dL, and during hyperglycemia was 306 ± 58 mg/dL (Kelly et al., 2010). This study found that most participants displayed peak performance when blood glucose values were in the “acceptable” or target glycemic range. Of the 7 subjects tested while hypoglycemic, 1 subject scored his personal best. Three of 10 subjects performed best while “hyperglycemic”, and the remaining 24 subjects performed their personal best while in the “acceptable” glycemic range (Kelly et al. 2010). While the study did find most people fell within a specific range, there were still outliers.
It would be beneficial for all those living with diabetes to further evaluate these targets for athletes. I would hypothesize that the ideal exercise target for everyone is closely related to typical and overall blood glucose management.
Overall, as we know, in diabetes management there is never a one size fits all approach. If you would like assistance in finding what target is best for your preferred sport performance along with help keeping it there, give our office a call and set up an appointment! Our office number is 610-642-6055.
Kathryn received her Bachelor of Science in Exercise Physiology from Ave Maria University in Florida and a Master's degree in Clinical Exercise Physiology from West Chester University in Pennsylvania. She is Certified by the American College of Sports Medicine as well as the International Sports Science Association.