How to train for triathlon with type 1 diabetes

You might think that a type 1 diabetes diagnoses means you’re not able to train and race successfully in multisport. Well you’d be wrong. With a considered ‘glucose management plan’ there’s no reason you can’t enjoy one of the greatest sports on earth! Here’s everything you need to know…

What is type 1 diabetes?

Type 1 diabetes is characterised by an absolute or relative lack of insulin, due to autoimmune destruction of the insulin secreting β-cells of the pancreas. Eventually, this results in a dependency on injectable or pump-driven insulin therapy to manage blood glucose concentrations within a healthy range.

How does it affect an individual?

The acute effects of too much insulin can result in hypoglycaemia (blood glucose less than 3.9 mM) while too little insulin results in hyperglycaemia (high glucose values more than 10 mM), respectively. The physiological effects of ‘having a hypo’ can be neuroglycopenic (e.g., confusion, or unconsciousness) and neurogenic (pallor, sweating, tachycardia and hunger) symptoms.

On the other hand, long-term hyperglycaemia damages nerves and blood vessels around organs such as eyes, kidneys, feet, and heart. Thus, management of blood glucose is of primary importance for people with type 1 diabetes.

• Hypoglycaemia versus hyperglycaemia: what’s the difference?

How does it affect triathletes in terms of their training and racing nutrition and performance?

It’s beyond this short overview to detail fully the considerations for exercise as a person with type 1 diabetes. The reader is encouraged to always check with their GP or healthcare professional for suitability to engage in a vigorous sport like triathlon.

However, if cleared to exercise, a person with type 1 diabetes should always consider the following elements for the maintenance of blood glucose during exercise: insulin, carbohydrate and exercise, which is easily remembered by the acronym, ICE.

Monitoring blood glucose is crucial during a triathlon, because glucose disappears quickly into working muscle by a mechanism that is separate from, but in addition to, insulin-driven glucose uptake.

Continuous glucose monitoring devices (available on the NHS) are small implantable sensors that are inserted under the skin to provide near-real time glucose values. Glucose data can be displayed on sports watch faces or mobile phone apps to enable rapid decision making based on displayed glucose values arrow trajectory.

During triathlon training or racing, frequent monitoring may encourage regular feeding to maintain safe blood glucose ranges and help performance.

Recently published work on professional cyclists with type 1 diabetes demonstrate large energy intakes during training and racing ^1,2. For carbohydrate intake to help maintain blood glucose we found athletes with type 1 diabetes typically consume around 0.70 gram per kg body mass per hour of endurance exercise, but this is highly individualised.

Notwithstanding, this translates into ~ 50 gram CHO per hour (in solids and fluid form) and helps maintain safe glucose levels during exercise ³.

How can athletes with type 1 diabetes train and race effectively?

Training is a great way to gradually develop a ‘glucose management plan’ that can be carried forward into racing. The primary aim should be to mimic the natural physiological response to preserving glucose concentrations during exercise.

Typically, the normal functioning pancreas suppresses insulin release into the circulation during exercise to offset increasing uptake of circulating glucose by muscle.

However, this is not possible in the person with type 1 diabetes as once insulin is injected it cannot be switched off and may add to the effect of exercise-induced glucose uptake. Thus, careful consideration of the amount, type and timing of insulin taken before exercise is warranted ³.

In addition to insulin alterations, eating a carbohydrate rich meal before exercise will ensure sufficient liver and skeletal muscle stores and aid in attaining adequate starting blood glucose concentrations ³.

During the triathlon, frequent monitoring of glucose concentrations will help encourage regular feeding that maintains blood glucose levels and supports triathlon performance.

How can athletes with type 1 diabetes best manage their glucose levels and recovery when training?

After a training session is over, the challenge of managing glycaemia remains. Triathletes are in an ‘insulin sensitive state’ with accelerated glucose uptake into liver and skeletal muscle. This might lead to the development of post-exercise hypoglycaemia (possibly in the night).

Athletes may need to make individualised insulin adjustments after exercise with a recovery meal dependent on the length and characteristics of the race (duration and intensity) of triathlon among other factors. The recovery meal (which should be protein and carbohydrate rich) can be consumed with a sports drinks post-event as this can aid carbohydrate provision and ensure hydration⁴.

Thus, monitoring blood glucose is important and it is here continuous glucose monitors (with low glucose alarms) are very helpful ⁵.

• How to recover from racing triathlon
• The big sports nutrition debate
• What type of protein is best for triathlon recovery?
• Triathlon nutrition: how to get fuelling right

Top image: Getty Images