VOLUME 9 NUMBER 4 • NOVEMBER 2012
187
SA JOURNAL OF DIABETES & VASCULAR DISEASE
REPORT
intensity/duration of exercise are required
to elicit glycaemic benefit, a large segment
of primarily young patients choose to par-
ticipate in recreational and extreme sports.
However, many of these patients do not
understand the complex relationship that
exists between exercise and type 1 diabe-
tes.
The metabolic challenges of exercise in
type 1 diabetes include:
the effect of duration and intensity of
•
exercise on glycaemic excursions
the pharmacokinetics of insulin, includ-
•
ing the variability of insulin, and vari-
ous exercise and environmental factors
affecting insulin absorption
the threats of hypo- or hyperglycaemia
•
during and after exercise.
Intensity of exercise:
in terms of exercise
intensity, more hypoglycaemia may occur
with low- or moderate-intensity exercise
such as walking, jogging and cycling. High-
intensity exercise, such as sprinting, results
in a significant catecholamine response
leading to hepatic dumping of glucose, and
hyperglycaemia. Intermittent type activities
such as spinning, soccer and hockey appear
to result in more stable glucose levels both
during and after the activity.
Factors influencing insulin absorption:
insulin absorption may be affected by dif-
ferences in blood flow with different types
of exercise. More hypoglycaemia occurs
with endurance exercise compared to
resistance exercise. Ambient temperature
and altitude also affect insulin absorption.
Warmer exercise environments will lead
to vasodilatation and better absorption
of insulin. Cold environments at rest may
cause vasoconstriction which may result in
poor insulin circulation and therefore hyper-
glycaemia. However, exercise in a cold envi-
ronment, such as swimming may still lead
to hypoglycaemia due to increased glucose
uptake to generate heat in the muscle.
Insulin resistance and therefore hyper-
glycaemia may occur at extreme altitudes
as a result of hypoxia. Good hydration levels
allow for more efficient absorption and cir-
culation of insulin. Injection site, injection
depth and injection technique will also influ-
ence the pharmacokinetics of insulin.
Hypoglycaemia:
A biphasic drop in blood
glucose level may occur with moderate-in-
tensity endurance-type exercise in the late
afternoon. This blood glucose drop may
occur initially while exercising and then again
seven to 11 hours later. In order to reduce
the risk of hypoglycaemia during exercise, it
is suggested that one should exercise before
breakfast or before supper. Insulin resistance
may be higher at dawn and dusk and there-
fore the chance of becoming hypoglycaemic
at these times is lower.
However, late afternoon exercise does
pose the threat of hypoglycaemia occur-
ring unnoticed during sleeping hours. Noc-
turnal hypoglycaemia can be managed by
decreasing the bolus insulin dose at dinner
time and the basal dose at bedtime, and
eating a protein snack to give a sustained
energy source throughout the night. Mr
Heilbrunn also recommends increasing car-
bohydrate intake prior to and during exer-
cise to prevent hypoglycaemia.
Carbohydrate intake can be determined
by the body mass and the duration and
intensity of exercise, with the recommen-
dation of 1.0 g carbohydrate/kg/hour. If
participating in higher-intensity and long-
duration exercise, a post-exercise glycogen
replenishment drink (consisting of 0.8 g/kg
carbohydrate and 0.4 g/kg protein) with a
low dose of insulin is advised.
A reduction in insulin dosage prior to
exercise may also be appropriate to avoid
hypoglycaemia and there are certain guide-
lines available in the literature. Mr Heilbrunn
suggested that insulin pump therapy may
pose a solution to exercise-induced hypogly-
caemia. There is the option of disconnecting
during exercise, or decreasing basal insulin
rates for an appropriate time before, during
and after exercise. Basal insulin rates can
also be adjusted at critical times during the
night to decrease the incidence of nocturnal
hypoglycaemia with exercise.
Hyperglycaemia:
Hyperglycaemia may
be common in exercises such as squash or
high-intensity spinning or high-intensity
resistance training, due to an excessive
counter-regulatory hormonal response.Most
type 1 diabetes patients choose to exercise
during the tail effect of their insulin action,
or they will decrease their insulin dosage in
order to avoid hypoglycaemia. Therefore the
post-exercise insulin levels may be low.
With high post-exercise circulating coun-
ter-regulatory hormones and low insulin
levels in the type 1 diabetes patient, the
counter-regulatory response remains high
and the patients’ blood glucose levels may
remain high for a number of hours post
exercise. Competition days and extra car-
bohydrates will exacerbate the problem. It
is suggested that one to two units of insulin
prior to exercise and/or after exercise may
counteract this hyperglycaemic effect.
In summary, Mr Heilbrunn stated that
the management of diabetes and exercise
requires consideration of the complex inter-
actions that make a single generic formula
inappropriate. Our physiological under-
standing can help guide individuals, but it
cannot replace the importance of individu-
als monitoring their own blood glucose
response to a particular exercise. He does
feel that regular activity on a daily basis or
on alternate days should be recommended.
Through regular activity, people with type 1
diabetes will improve their insulin sensitivity
and learn to manage hypoglycaemia and
hyperglycaemia with exercise.
Diabetes in the elderly
Dr Stan Landau, specialist physician,
Centre for Diabetes and Endocrinology,
Houghton, Johannesburg
Diabetes is a power-
ful predictive factor of
a decrease in success-
ful aging. One in five
peopleover the ageof
65
years will develop
type 2 diabetes, and
diabetes in the elderly
needs to be seen as a
specific entity under
the broader diabetes
umbrella. Dr Landau
said that elderly is
generally defined as a spectrum starting at
60,
but that his focus would be mainly on
patients aged 75 and older.
On a positive note, increased diabetes-
related mortality at a later age is relatively
low. From 1997/98 to 2000/03, there was
a 40% reduction in cardiovascular mor-
tality in diabetes and a 23% reduction in
all-cause mortality. ‘People with diabetes
are living longer and dying less often from
cardiovascular disease. The irony, how-
ever, is that this decline in mortality means
we will see increasing numbers of elderly
patients with diabetes remaining alive and
requiring care.’
Both the pathophysiological processes
and the clinical presentation of diabetes in
the elderly are atypical, relative to patients
who developed the condition at a younger
age. In lean elderly patients, the predomi-
nant pathophysiological pathway is insulin
deficiency whereas in the obese it is insulin
resistance. Lean patients still harbour seri-
Dr Stan Landau
1...,35,36,37,38,39,40,41,42,43,44 46,47,48,49,50,51,52