CLINICAL CONDITIONS

EXERCISE AND NON-INSULIN DEPENDENT DIABETES MELLITUS

Diet, medication and exercise are the three cornerstones of treatment for diabetes, but exercise is often overlooked in primary care advice in spite of its significant benefits both in the treatment and prevention of this condition.

Diabetes is a common disorder that affects 1-2% of the population by interfering with the body's sensitivity to insulin, the hormone which helps control blood sugar levels. It is caused either by failure of the pancreas – type 1 or insulin-dependent diabetes mellitus (NIDDM), or because the body develops a resistance to insulin – type 2 or non- insulin dependent diabetes mellitus (NIDDM).

More than 750,000 people in the UK have diabetes, of whom over 80% are non-insulin dependent, the form that occurs more commonly in adulthood. Research has shown NIDDM has a strong genetic component, but conditions such as obesity and advancing age also significantly increase the risk. In Britain about 75% of NIDDM patients are overweight.

Exercise in the

prevention of NIDDM Data from the University of Pennsylvania Alumni Health Study shows good evidence of an inverse relationship between exercise energy expenditure and the development of NIDDM in the subsequent 15 years.

A study of 6,000 subjects aged 45-68 compared physical activity levels with the development of NIDDM. The results showed that for each 500 kcal/wk increase in energy expenditure, the risk of developing NIDDM reduced by 6% after adjusting for age, body mass index and family history.

Two thirds of the new cases of NIDDM were obese hypertensives with a family history of diabetes. In this high risk subgroup, physical activity had the

10 SportEX

Studies have shown that spreading the activity over, for example, three 10- minute bouts is as effective as one 30- minute session. It is important to stress to patients that physical activity does not have to be a sport and many household activities count.

Diabetes can lead to reduced efficiency of the nerves controlling body functions such as heart rhythm and sweating which means patients are at greater risk of postural hypotension. Thorough warm downs should be advised to minimise this possibility.

greatest protective effect with a 24% reduction in incidence in the most active subjects.

Benefits of exercise

in NIDDM Exercise has two main effects on blood glucose control: it increases the body’s sensitivity to insulin and it promotes the uptake of glucose from the blood into the muscles.

Peripheral insulin sensitivity is increased in both diabetic and non-diabetic subjects during exercise but this enhanced action is lost within a few days and regular physical activity is necessary to maintain these benefits.

Regular exercise also helps lower plasma insulin levels as well as reducing other cardiovascular disease risk factors including obesity, hypertension and hyperlipidaemia.

Exercise advice

New recommendations of moderate intensity activities where the exerciser becomes moderately breathless and sweaty, ideally for 30 minutes on at least five days of the week have superceded those of vigorous activity which increase cardiovascular risk.

Regularly exercising diabetics, whether they are dependent on insulin or not, can take part in a whole range of sporting activities. But they need to be adequately prepared and have a good understanding of their disease.

Exercise should be avoided until diabetes is adequately controlled and body fat metabolism has been stabilised. There should be no evidence of abnormally raised concentrations of body fat metabolites such as ketone bodies which could lead to an imbalance of acids in the body and a malfunctioning of some organs in the body such as the kidney.

Potential hazards of exercise in NIDDM

1 Cardiovascular disease

Male and female diabetics have two and three times the incidence of coronary heart disease of non-diabetics respectively. It may be ‘silent’, that is the patient does not have the typical pain of angina when coronary ischaemia occurs. People on insulin or with retinopathy have approximately two and a half times the prevalence of silent ischaemia than those with NIDDM.