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Hi there!
Today we’ll have a deeper look into a type of PA for T1D subjects. If you don’t know what diabetes is, click on the following link (Diabetes: another type of NCD) to have more details.
Despite metabolic control in type 1 diabetes (T1D) is still uncertain, it is important to include the practice of physical activity (PA) in the management of T1D since it increases insulin sensitivity (both short and long term), reduces blood glucose levels, reduces fat mass and enhances cardiovascular response.

Abnormal endocrine responses to exercise and dysmetabolism into T1D

The correct balance between the production and use of glucose during exercise, maintained from GH, insulin, cortisol, glucagon and epinephrine, is reduced or lost in T1D.
Even the normal energy metabolism functions are modified as follows:
–Glycolysis: an intensive and short physical exercise induces glycogen degradation to ensure an adequate and constant energy intake. However, when insulin levels are too high, glycogen degradation is inhibits and glycogenolytic response is reduced.
–Lipolysis:  is activated when the blood glucose level is reduced during exercise. Nevertheless, it is also attenuated when high circulating insulin levels are there.
–Proteolysis: is an alternative energy source when the glucose is not available as a primary fuel. But, also, in this case, elevated circulating insulin levels can mitigate this process.

Exercise in T1D

Aerobic exercise improves insulin sensitivity and blood lipid profile; reduces blood pressure and cardiovascular disease (CVD) risk; increases energy expenditure and physical performance; counteracts diabetes’ symptoms.
The American Diabetes Association (ADA) recommends every day at least 60 minutes of moderate-intensity exercise (50-69% VO₂max) or at least 25 minutes of vigorous-intensity exercise (70-85% VO₂max) three times a week.
Resistance training is important to counteract typical conditions of T1D such as atrophy, loss of dimension and number of type 2 fibres, strength reduction and hypoglycemic events.
The ADA recommends performing 8-10 exercises from moderate to vigorous intensity (1-3 sets of 10-15 reps) for 2-3 non-consecutive times a week.
However, before engaging in an exercise program, comorbidity and chronic diseases presence like neuropathy, retinopathy, nephropathy, CVD have to be considered.

Hyperglycemic and hypoglycemic risk

When levels of insulin are too high, hypoglycemic risk occurs. It happens when glucose uptake increases, while hepatic glucose production, lipolysis and stress hormones decrease.
Typical hypoglycemia symptoms are weakness, tiredness, dizziness, paleness, sweating, tachycardia, headache. In this case, it is advisable to stop exercising, to measure blood sugar and, if it is necessary, to take fast-absorbing carbohydrates.
A hypoglycemic event can mostly occur with aerobic exercise because it is at low intensity and has a long duration.
However, weight training before aerobic exercise can be used to maintain adequate blood sugar levels in T1D.
On the other hand, when levels of insulin are too low, hyperglycemic risk occurs. It happens when glucose uptake reduces, while hepatic glucose production, lipolysis and stress hormones increase.
A hyperglycemic event can mostly occur with anaerobic exercise because it increases catecholamines and cortisol levels. While in healthy subjects this phenomenon is compensated by the enhanced post-exercise insulin secretion, in T1D subjects the increase of these hormones could exacerbate post-exercise hyperglycemia.
However, anaerobic sprint (for maximum 10 seconds) can help to prevent hypoglycemic events in the immediate post-exercise. 

Useful considerations

During the day, carbohydrate intake and insulin injection must be regulated to prevent dysglycemic events.
Moreover, blood glucose levels should be monitored before exercise (at least two measurements at a distance of 15-45 minutes from each other) and during exercise (every 30 minutes).
If the blood glucose level is greater than 250-300 mg/dl it is recommendable to avoid or stop the exercise or, if it is lower than 100 mg/dl, it is advisable to stop the training session and to take fast-absorbing carbohydrates. When blood glucose levels are normalized, the exercise session can start again.
Because of elevated insulin sensibility up to 12 hours after exercise, it is important to keep checking blood glucose levels to prevent late hypoglycemic events.

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References
Roberto C., et al – Why should people with type 1 diabetes exercise regularly? Acta Diabetol – 2019;

Edited by
Dott. Luca Rotundo