The Exercise and Type One Diabetes (EXTOD) conference of 2023 hosted sessions focused on physiological and metabolic responses to exercise whilst teaching management strategies to overcome type 1 diabetes glucose challenges. The critical insights throughout the two days provided a framework for supporting people with type 1 diabetes who want to exercise. Furthermore, there was a session from Psychologist, Dr Josephine Perry, on how to be BRAVE. This session led to me creating the imaginary figure “Imposter John”. More on how to become BRAVE at the end.
The physiology sessions shed light on the interplay between insulin-independent and insulin-dependent pathways that affect glucose uptake during exercise. It was highlighted that GLUT-4 translocation can occur independent of insulin, which, when combined with insulin-dependent uptake, can significantly raise the risk of hypoglycaemia during physical activity.
A primary concern discussed was the impact of subcutaneous insulin, specifically its extended half-life, which results in peripheral insulin levels being 2.5 to 4 times higher in individuals with type 1 diabetes compared to those without the condition. The comparison of peripheral insulin to a “sledgehammer” in its overpowering effect against adrenaline and glucagon underlines the challenge it poses, especially when large amounts of insulin are present in the blood.
Interestingly, it was noted that in circumstances where only basal insulin levels are prevalent (absence of a bolus insulin in the last 3-4 hours or while fasting), an adrenaline surge from high-intensity exercise could trigger a glucose rise due to liver glycogenolysis.
The session also presented an analysis of clinical trials that pinpointed several factors leading to significant glucose level drops during exercise. According to Eckstein et al.’s 2023 study in Diabetic Medicine, running was found to cause greater glucose reductions compared to cycling, due to the engagement of more muscle groups. Furthermore, both the duration and the intensity of the exercise were directly proportional to the extent of the glucose drop.
Turning to real-world evidence, Bergford et al 2023, the session revealed findings from a study involving close to 500 adults with type 1 diabetes who recorded nearly 10,000 exercise sessions. The data gathered identified four predominant factors associated with the risk of hypoglycaemia. The most critical factor was the pre-exercise glucose level, followed by the rate of glucose change indicated by trend arrows, the amount of insulin on board, and the type of exercise performed.
Taking all these points on board, several management strategies were discussed. First, how much carbohydrate is needed when using blood glucose testing and Continuous Glucose Monitoring (CGM)? The EXTOD advice is here.
The ISPAD 2022 Exercise Guidelines carb amounts are here for those using finger pricks
This is how to implement it practically.
The ISPAD 2022 Exercise Guidelines carb amounts are here for those using CGM.
- Dexcom G6 – Exercise Carbohydrate Calculator
- Libre 1 & 2 – Exercise Carbohydrate Calculator
- Medtronic – Exercise Carbohydrate Calculator
- Dexcom G6 with pump – Exercise Carbohydrate Calculator
Then it’s all about insulin onboard. The take-homes were:
- Aim to have last meal and insulin three hours before exercise for the most consistent glucose levels
- If eating within 2 hours of exercise, reduce the usual dose by ~50%
- If possible, try to exercise within 60 minutes of insulin reductions to prevent going too high before starting exercise.
Type of exercise is important, but, if exercise is within two hours of bolus insulin, the glucose is very likely to drop irrespective of exercise type.
Insulin sensitivity is high immediately after exercise necessitating a 50% insulin reduction at the meal after exercise. Furthermore, if the exercise is after 4 pm, a 20% reduction in background basal insulin or 20g of carbs without fast acting before bed if the glucose level is less than 10 mmol/L. If the glucose level is less than 7 mmol/L consider adding 10-20g protein.
How do you make a plan with all this information?
Simply start with 50/50/20 and this useful table from the ISPAD Guidelines 2022.
What about Hybrid Closed Loop Therapy?
Are the exercise plans different for HCL or AID if you prefer that term?
This publication led by Dessi is amazing for the top tips.
This is a simplified algorithm to get started.
Several HCL device-specific considerations were discussed.
People who already have good exercise plans may be better off going into the open loop two hours before starting the exercise. This enables the person to be sure of the insulin conditions to get reproducibility in glucose variability for the same plan. Then switch the loop back on after exercise to reap the benefits of reduced hypoglycaemia risk.
I encourage you to go to the EXTOD to get more details. The EXTOD site contains excellent information to support people living with type 1 diabetes to mange exercise.
Psychology Session: Josephine Perry – BRAVE
In this session, Josephine Perry explores how our amygdala perceives threats, which are then addressed either rapidly through habit or more deliberately through decision-making. When our brain’s wiring has a low threshold for perceiving something as a threat, and if habits responding to these threats are established, this can result in significant anxiety. The key is to become more conscious of these perceived threats and to contemplate them more thoroughly, aiming to develop a new “habitual” relationship with how we perceive threats. This requires dedicated effort.
- Threat: The amygdala, symbolised by the thumb, predicts threats, triggering fight or flight responses.
- Habit: Represented by the palm of the hand, the mid-brain operates automatically, forming habits in roughly 66 days.
- Decision: The pre-frontal cortex, depicted by the fingers, is involved in slower, more deliberate decision-making.
Factors contributing to a low threshold for perceiving threats include previous trauma, overthinking, perfectionism, judgmental attitudes, external rewards, recent failures, fear of failure, and self-identity as an athlete.
Situational factors that can lower the threshold for perceiving threats include hunger, tiredness, encountering a nemesis, low glucose levels, and having one’s values violated.
To counteract these issues, one must be BRAVE and “think differently”:
- B: Be aware of your worries and verbalise what the amygdala is signalling, creating a sense of safety.
- R: Reassign these worries to your ‘safety seekers’ and create characters for them, like “Lazy Larry” or “Imposter John”.
- A: Advocate for yourself using positive affirmations at a ratio of 5 to 1 to counteract negative thoughts.
- V: Focus on your values; identify your top three from a list of 100, such as fairness, challenge, and progress.
- E: Engage in simple strategies to combat anxiety, such as breathing exercises, grounding, CBT strategies, smiling, and chunking.
My example of working through this process:
- Beware of thoughts like feeling like an imposter when contacting others.
- Reassign these thoughts to a character, “Imposter John”.
- Advocate for oneself by recognising one’s valuable insights.
- Focus on values such as curiosity, challenge, and fairness.
- Engage in open communication with the mindset of having “Strong convictions, loosely held”.
Thus, by envisioning an imaginary friend like “Imposter John”, one can learn to think more slowly about perceived threats, facing fears and acting despite them. Special thanks to Josephine Perry for these insights.