Physical activity

Physical activity is one of the cornerstones of diabetes management. Regular physical activity of any kind can have a favourable impact on glycaemic control, CVD risk and overall mortality.⁶ However, more structured, specialised and individualised exercise prescription can achieve superior benefits.¹⁰

The goal is for patients with diabetes, impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) to accumulate a minimum of 210 minutes per week of moderate-intensity exercise (or 125 minutes per week of vigorous-intensity exercise), with no more than two consecutive days without training. This weekly total should include at least two moderate-to-vigorous resistance training sessions for a total of at least 60 minutes. These exercise amounts will establish and maintain muscular fitness and aerobic capacity.⁴

It is recommended to refer patients with type 2 diabetes to an accredited exercise physiologist for the prescription of a safe and effective exercise intervention.

Aerobic exercise

In people with type 2 diabetes, aerobic exercise (eg walking, cycling, swimming) reduces HbA1c, triglycerides, blood pressure and insulin resistance.¹⁰

Aerobic exercise intensity can be set as a percentage of estimated maximal heart rate (HR_max) using the equation 208 – 0.7 x age [years].^11,12 For moderate intensity, 55–69% of HR_max and for vigorous intensity 70–89% of HR_max can be used.⁴

Alternatively, ‘moderate’-intensity aerobic exercise is defined on rate of perceived exertion (RPE) scales as ‘somewhat hard’, and ‘vigorous’ as ‘hard’. Using the talk/sing test, a person is doing moderate-intensity exercise when they can comfortably talk but can’t sing, and vigorous is when they are unable to talk comfortably.

Resistance exercise

Resistance, or strength, training involves activity such as using free weights, resistance machines or body weight. ‘Moderate-to-vigorous’ resistance training can be defined as 2–4 sets of 8–10 repetitions of 8–10 exercises, with rest intervals of 1–2 minutes.⁴

Resistance training reduces HbA1c, although to a lesser degree than aerobic exercise.¹³ However, combining aerobic and resistance training appears to be superior compared with either alone.¹⁴ Both types reduce CVD markers similarly,¹³ and a single bout of either may have a similar acute effect.¹⁵

When advising patients about physical activity, general practitioners (GPs) should:

• emphasise that some physical activity is better than none¹⁰
• discuss the importance of reducing sedentary behaviour – advise patients to interrupt prolonged sitting every 30 minutes for blood glucose benefits
• explore the risks and benefits of different forms of physical activity for the individual, taking into account whether the patient is already physically active
• explain the importance of varying intensity of exercise levels
• explain the importance of following the chest pain/discomfort and/or diabetes symptom management plan.¹⁶

Pre-exercise health assessment

Asymptomatic sedentary people with diabetes who wish to undertake low-to-moderate activity should have CVD assessment as part of usual diabetes care; however, those identified as having CVD risk on screening tools, or who have existing atherosclerotic or functional cardiovascular disease, may require more specific physical assessment prior to engaging in moderate- to high-intensity exercise. Existence of diabetes complications may require specific advice – refer below.

When prescribing a physical activity program, the GP should take a careful history and be aware of the following:

• Special attention needs to be paid to exertion-induced symptoms, chest or abdominal discomfort, claudication or syncope.
• People with type 2 diabetes frequently have silent macrovascular disease.
• For patients with hypertrophic obstructive cardiomyopathy, heavy weightlifting and high-intensity aerobic exercise are not recommended.¹⁷
• For patients with long QT syndrome, exercise may trigger a cardiac arrhythmic event.¹⁷
• Vigorous exercise is contraindicated for those with proliferative retinopathy, and for three months after laser retinal treatment.¹⁷
• Exercise may be relatively contraindicated in patients with peripheral neuropathy, a history of recurrent falls or uncontrolled hypertension.¹⁷
• A foot assessment should be carried out and patients advised about the importance of appropriate footwear during exercise.
• Referral to an accredited exercise physiologist is recommended.

Any symptoms suggestive of CVD need to be actively investigated.

Safety advice during and after exercising

People with diabetes should be advised to moderate or cease their activity if they develop cardiovascular symptoms or feel unwell.

Patients with claudication need to be encouraged to continue physical activity under appropriate clinical supervision.

Managing blood glucose levels

People using insulin or sulfonylureas (or combinations including these) need to be aware of potential delayed effects of physical activity on blood glucose levels (BGLs) – in particular delayed hypoglycaemia. Post-exercise hypoglycaemia can occur 12–15 hours after exercise, but is still a risk up to 48 hours after cessation of activity.¹⁰

Advise patients on how to recognise, prevent or manage hypoglycaemic events, including potential post-exercise hypoglycaemia (Box 1). Clinical advice should be given to all patients to stop physical activity if they experience symptoms of hypoglycaemia and to discontinue further physical activity until reviewed by their GP or other health professional.

Other exercise safety advice

• Advise patients to wear correct supportive footwear – especially if there is neuropathy, vascular disease, abnormal foot structure or previous foot ulcer/s, in which case the advice of a podiatrist with an interest in high-risk feet should be sought. This advice would also include the appropriateness of ‘jolting’ exercises such as running, skipping and jumping.
• Advise patients with neuropathy or peripheral arterial disease to check their feet daily and after physical activity for blisters, warm areas or redness.