NUTRITION IN SPORT

concentration should lead to the postponement
of exercise for the reasons given above. The dose
of insulin administered before any exercise
should be scaled down to reflect the degree of
intensity and duration of exercise. However,
individual IDDM subjects may have to reach the
optimum pre-exercise insulin dose by monitor-
ing post-exercise glucose levels.

Non-insulin-dependent

diabetes mellitus

NIDDM is a world health problem and the
disease is often regarded as a disease of abnor-
mal lifestyle. About 90% of all diabetics are
NIDDM and the disease develops gradually and
is normally associated with obesity and hyper-
tension. Initially, the skeletal muscles and liver
becomes insulin resistant, but the body responds
by producing more insulin and glucose con-
centration remains normal. However, as the
insulin resistance increases, the pancreas
becomes unable to produce enough insulin to
regulate the metabolism of blood glucose con-
centration and hyperglycaemia occurs.
The pharmacological treatment of NIDDM is
poor. As the muscles are insulin resistant, insulin
therapy is not a satisfactory treatment of the
disease. There are some other drugs prescribed,
such as sulphonylureas and metformin. NIDDM
is in most case initially treated with dietary
manipulation and exercise. This treatment is
sufficient for many people with NIDDM if the

disease has not progressed too far. Exercise of

moderate intensity in people with NIDDM is

usually associated with a decrease in blood

glucose towards the normal range. A further

benefit of regular exercise is that it increases the

sensitivity of skeletal muscle to insulin, which

will have the beneficial effect of lowering the

requirement for circulating insulin concentra-

tion. It is important to recognize that exercise also

lowers the risk factors for cardiovascular disease

in people with NIDDM.

Exercise training for NIDDM

NIDDM is normally associated with obesity and

a low exercise capacity. NIDDM develops later in

life than IDDM and the majority of patients are

over 50 years old. The aims of exercise training

for people with NIDDM are therefore often dif-

ferent from those of young people with IDDM.

People with NIDDM are often untrained and an

improved level of physical fitness is normally the

main goal. As for untrained people in general,

there are large opportunities for improvement

and training studies have shown that endurance

training increases maximum oxygen uptake and

oxidative capacity in skeletal muscle (Wallberg-

Henriksson 1992).

Obesity may hinder training and a high body

mass increases the risk of injury to joints and

tendons. In people with NIDDM, it is also impor-

tant to be aware of the risk for foot problems, par-

ticularly in diabetics with peripheral neuropathy,

the diabetic athlete 463

Exercise Recovery

02 4 6 8 10 12

(mmol

.kg

–1

wet wt)

Muscle glycogen content

80

60

40

20

0

Time (h)

Fig. 34.3Glycogen synthesis in
IDDM subjects after exercise in the
presence () or absence () of
insulin. Subjects exercised at 75% of
V
.
o2max.until exhaustion and
received a carbohydrate-rich diet
and their normal insulin injection in
the control experiment. On the
other experimental day, insulin was
not injected. Adapted from
Mæhlumet al.(1978).