Michael C Riddell, Ian W Gallen, Carmel E Smart, Craig E Taplin, Peter Adolfsson, Alistair N Lumb, Aaron Kowalski, Remi Rabasa-Lhoret,
Rory McCrimmon, Carin Hume, Francesca Annan, Paul A Fournier, Claudia Graham, Bruce Bode, Pietro Galassetti, Timothy W Jones,
Inigo San Millan, Tim Heise, Anne L Peters, Andreas Petz, Lori M Laffel
Type 1 diabetes is a challenging condition to manage for various physiological and behavioural reasons. Regular
exercise is important, but management of different forms of physical activity is particularly difficult for both the
individual with type 1 diabetes and the health-care provider. People with type 1 diabetes tend to be at least as inactive
as the general population, with a large percentage of individuals not maintaining a healthy body mass nor achieving
the minimum amount of moderate to vigorous aerobic activity per week. Regular exercise can improve health and
wellbeing, and can help individuals to achieve their target lipid profile, body composition, and fitness and glycaemic
goals. However, several additional barriers to exercise can exist for a person with diabetes, including fear of
hypoglycaemia, loss of glycaemic control, and inadequate knowledge around exercise management. This Review
provides an up to date consensus on exercise management for individuals with type 1 diabetes who exercise regularly,
including glucose targets for safe and effective exercise, and nutritional and insulin dose adjustments to protect
against exercise-related glucose excursions.
Despite tremendous advances since the discovery of
insulin almost 100 years ago, management of type 1
diabetes remains challenging.1,2 The majority of patients
living with type 1 diabetes do not have a healthy body
weight (about 60% are overweight or obese), about 40%
have hypertension, about 60% have dyslipidaemia,3 and
most do not engage in enough regular physical activity.4
Regular exercise can help patients achieve several goals: it
improves the cardiovascular disease risk profile in
paediatric patients5 and reduces HbA1c by about 0.3% in
the paediatric population.6 Body composition,
cardiorespiratory fitness, endothelial function, and blood
lipid profile (ie, triglycerides and total cholesterol) all
improve with regular physical activity in children and
young people with type 1 diabetes.6 These cardiometabolic
improvements are all important, given that cardiovascular
disease is the leading cause of morbidity and mortality in
young people with type 1 diabetes.7,8 In adults, both
retinopathy and microalbuminuria are less common in
those who are physically active than in those who are not.9
Active adults with type 1 diabetes tend to have better
chance of achieving their HbA1c and blood pressure targets,
and a healthier BMI, than do inactive patients.3 Regular
exercise also decreases total daily insulin needs.10 Having a
high exercise capacity in adulthood is associated with a
reduced risk of coronary artery disease, myocardial
ischaemia, and stroke, regardless of whether a person has
diabetes or not.11 In a large cross-sectional study of 18 028
adults with type 1 diabetes,3 patients who were categorised
as being most physically active (exercising two or more
times per week) had better HbA1c concentrations, a more
favourable BMI, less dyslipidaemia and hypertension, and
fewer diabetes-related complications (retinopathy and
microalbuminuria), than those who were less habitually
active. The study also showed that patients with type 1
diabetes who are more active tend to have less diabetic
ketoacidosis and a reduced risk of developing severe
hypoglycaemia with coma.3 However, older women who
are physically active have higher rates of severe
hypoglycaemia (with coma) than those who are inactive.3
Several barriers to exercise might exist, including a fear of
hypoglycaemia, loss of glycaemic control, insufficient
time, access to facilities, an absence of motivation, issues
around body image, and a general scarcity of knowledge
around exercise management.12–14
For all adults living with diabetes, including those
living with type 1 diabetes, 150 minutes of accumulated
physical activity is recommended each week, with no
more than two consecutive days of no physical activity.15
Resistance exercise is also recommended two to three
times a week.15 Getting this much exercise is difficult for
many patients; results from a large cross-sectional study
showed that less than 20% of patients manage to do
aerobic exercise more than two times per week, and
about 60% of patients do no structured exercise at all.3
For children and young people, at least 60 minutes of
physical activity should be done per day.16 Physical
inactivity and prolonged sitting times increase gradually
with age and are linked to high HbA1c concentrations in
young people with type 1 diabetes,17 and physical inactivity
appears to be more common in women than in men.3
Regular exercise should be encouraged and supported
by health-care professionals for many reasons, but
primarily because the overall cardiometabolic benefits
outweigh the immediate risks if certain precautions are
taken. In this Review, the basic categories of exercise are
described from a physiological perspective, as are the
starting points for nutritional and insulin dose
adjustments to keep patients in a targeted glycaemic
range. This Review summarises the authors’ consensus
on the available strategies that help incorporate exercise
safely into the daily management plan for those adults
with type 1 diabetes who are regularly engaging in
exercise, sports, or competitive events. We hope these new
guidelines for exercise management will improve
glycaemic control and encourage more individuals with
type 1 diabetes to increase their physical activity.
Physiology of physical activity and exercise
Modalities of exercise
An understanding of the metabolic and neuroendocrine
responses to the various types of exercise done by people
with type 1 diabetes is essential for determination of
appropriate nutritional and insulin management
strategies. Exercise is generally classified as aerobic or
anaerobic, depending on the predominant energy
systems used to support the activity, although most
exercise activities include a combination of energy
systems. Aerobic exercise (eg, walking, cycling, jogging,
and swimming) involves repeated and continuous
movement of large muscle groups that rely primarily on
aerobic energy-producing systems. Resistance (strength)
training is a type of exercise using free weights, weight
machines, body weight, or elastic resistance bands that
rely primarily on anaerobic energy-producing systems.
High intensity interval training involves alternation
between brief periods of vigorous exercise and recovery
at low to moderate intensity (eg, from 20 s to 4 min
intervals of exercise and rest, for up to ten cycles).18 Both
aerobic and anaerobic activities are recommended for
most people living with diabetes,15,16 and guidelines now
also incorporate high intensity interval training as a
training modality with established benefits for individuals
with prediabetes or type 2 diabetes.15 In some studies,
high intensity interval training has been shown to be
more effective than continuous aerobic training in
improvement of cardiovascular fitness and various
parameters related to glucose metabolism, including
insulin sensitivity and glycaemic control in type 2
diabetes.19 At present, it is unclear what the most effective
forms of exercise for improvement of cardiometabolic
control in type 1 diabetes are.20
Neuroendocrine and metabolic responses to exercise
Individuals without diabetes
The metabolic responses to different forms of exercise
are distinct. However, in almost all forms of exercise,
regardless of the intensity or duration, blood glucose
concentrations are normally held within a tight range
(4–6 mmol/L). During aerobic exercise, insulin secretion
decreases and glucagon secretion increases in the portal
vein to facilitate release of glucose from the liver to match
the rate of glucose uptake into the working muscles.21
Exercise can increase glucose uptake into muscle by up
to 50 times—a phenomenon that occurs independently
of insulin signalling—22 so the decrease in circulating
insulin does not restrict glucose provision to the working
body. Although the main determinant of glucose
production during aerobic exercise is an increase in
glucagon concentrations, neural control of glucose
release and other counter-regulatory hormones also have
a supportive role.23 An extended duration of exercise
leads to reduced reliance on muscle glycogen as fuel and
increased reliance on lipid oxidation and glucose derived
from plasma.24 If insulin concentrations do not fall
during prolonged aerobic exercise (eg, walking, jogging,
or cycling), the rise in counter-regulatory hormones is
less effective than when they do fall in the promotion of
hepatic glucose production.21
When the intensity of exercise increases above 50–60%
of maximal oxygen consumption (VO2max), fat oxidation
decreases, particularly in those who are untrained, and
carbohydrates become the preferred fuel.25 Prolonged
high intensity exercise is supported by use of both muscle
glycogen and blood glucose, with minimal contributions
from lipid and protein.26 During predominantly anaerobic
activities such as springing,27 and during a high intensity
interval training session,28 circulating insulin
concentrations do not decrease as markedly as in purely
aerobic activities, in part because the duration of activity
is typically shorter. High rates of external power output
during high intensity interval training increase reliance
on muscle phosphagens and glycogen, with lactate
concentrations rising markedly in the circulation.28
Insulin concentrations increase above baseline
concentrations in early recovery from a high intensity
interval training session to offset the rise in glucose
caused by the elevations in counter-regulatory hormones
and other metabolites.27
Dysglycaemia during exercise in individuals with type 1 diabetes
In type 1 diabetes, the glycaemic responses to exercise
are influenced by the location of insulin delivery, the
amount of insulin in the circulation, the blood glucose
concentration before exercise, the composition of the last
meal or snack, as well as the intensity and duration of the
activity29 (figure 1).
During aerobic exercise, blood glucose concentrations
fall in most individuals with type 1 diabetes , unless they
ingest carbohydrates, because insulin concentrations
cannot be decreased rapidly enough at the start of the
activity and might rise in the systemic circulation,30
perhaps because of increased blood flow to subcutaneous
adipose tissue during exercise.31 Even if basal insulin
infusion rates are halved 60 min before the start of
exercise in patients on continuous subcutaneous insulin
infusion, circulating free insulin concentrations do not
decrease sufficiently upon commencement of exercise
and concentrations tend to increase transiently during
the activity.32 Increased insulin concentrations in the
circulation during exercise promote increased glucose
disposal relative to hepatic glucose production, and
might delay lipolysis—another feature that increases the
reliance of muscles on glucose as a fuel. Hypoglycaemia
develops in most patients within about 45 min of starting
aerobic exercise.33–35 Trained individuals with type 1
diabetes have greater reductions in blood glucose
concentrations during aerobic exercise than do
individuals with reduced physical fitness,36 possibly
because the overall work rate is higher in those who are
more aerobically conditioned than those who are not. As
such, both trained and untrained individuals with type 1
diabetes typically require an increased carbohydrate
intake [A: before commencing aerobic exercise?] or an
insulin dose reduction, or both, for prolonged aerobic
exercise. High intensity interval sprint training promotes
the increased oxidative capacity of skeletal muscle in type
1 diabetes and attenuates the rates of glycogen
breakdown,37 which might, in theory, protect against
hypoglycaemia after exercise. Perhaps in line with this,
individuals who are aerobically conditioned have lower
glucose variability than do those who are unconditioned.38
Low insulin concentrations due to aggressive reductions
in insulin administration or a skipped insulin dose can
cause hyperglycaemia before and during aerobic
exercise,39 and even mild activity could lead to
development of ketosis.40
Resistance exercise is associated with better glucose
stability than continuous moderate intensity aerobic
exercise,41 although resistance exercise could cause a
modest rise in glycaemia in some individuals.42
Compared with aerobic exercise, a high intensity interval
training session attenuates the decrease in glycaemia,43
as does resistance exercise done before aerobic exercise,44
possibly because of increased concentrations of counterregulatory
hormones and various metabolites that
restrict glucose disposal.45 In situations of brief and
intense anaerobic exercise (eg, sprinting, weight lifting,
and some competitive sports),42,46 or during high intensity
interval training,28 glucose concentrations typically rise.
Dysglycaemia after exercise in individuals with type 1 diabetes
Glucose uptake into muscle decreases immediately after
aerobic exercise, but overall glucose disposal remains
elevated for several hours in recovery from exercise to
help replenish glycogen stores.47 The risk of
hypoglycaemia is elevated for at least 24 h in recovery
from exercise, with the greatest risk of nocturnal
hypoglycaemia occurring after afternoon activity.48 As
mentioned above, weight lifting, sprinting, and intense
aerobic exercise can promote increase in glycaemia that
could last for hours in recovery. Although a conservative
insulin correction after exercise might be prudent in
some situations,49 over-correction with insulin can cause
severe nocturnal hypoglycaemia and lead to death.50 High
intensity interval training has been associated with a
higher risk of nocturnal hypoglycaemia than continuous
aerobic exercise in some51—but not all—52,53 studies.
Exercise goals and glycaemic targets
Individuals with type 1 diabetes should engage in exercise
for various health reasons. The evidence on whether
regular exercise improves metabolic control in adults
with type 1 diabetes is somewhat scarce,20,54 although
exercise appears to be helpful in young people with type 1
diabetes.6 Exercise readiness questionnaires, such as
Physical Activity Readiness Medical Examination
(ePARmed-X+) and Physical Activity Readiness
Questionnaire for Everyone (PAR-Q+), are available
online for adults with diabetes who might be at increased
risk of developing adverse events. Patient goals for
exercise (eg, metabolic control, prevention of
complications, fitness, weight loss, or competition and
performance) should be considered before decisions on
diabetes management are made. This is an important
element of the diabetes management plan. For example,
exercise for weight loss requires strategies that focus on
reduction of insulin concentrations during and after
exercise, as opposed to consumption of additional
carbohydrates. By contrast, if maximisation of sports and
exercise performance is the primary goal, then nutritional
guidance specific to the sporting activity is needed and a
modified insulin plan to match the increased nutritional
requirements should be considered.55 For all patients,
blood glucose monitoring before, during, and after
exercise is essential to inform strategies and maintain
stable and safe glycaemia.
The appropriate blood glucose concentration at the
start of exercise should be tailored to the individual.
Based on our consensus, a reasonable starting range for
most patients doing aerobic exercise lasting up to an
hour is 7–10 mmol/L. This range balances performance
considerations against the risk of hypoglycaemia.
Concentrations higher than 7–10 mmol/L might be
acceptable in some situations where added protection
against hypoglycaemia is needed. Achieving and
maintaining circulating glucose concentrations in this
range is challenging. The glycaemic response to exercise
is variable and based on several factors, including the
duration and intensity of exercise,45,56 the starting level of
glycaemia,34 the individual’s aerobic fitness,36 and the
amount of insulin in circulation57,58 (figure 1). Anaerobic
exercise and a high intensity interval training session
can be initiated with a lower starting glucose
concentration (5–7 mmol/L) because glucose
concentrations tend to remain relatively stable and fall
to a lesser extent than with continuous aerobic exercise,
or rise slightly (figure 1). Strategies to cope with a range
of glucose concentrations before the start of exercise are
provided in panel 1, bearing in mind that for aerobic
activities lasting longer than 30 min, additional
carbohydrates are likely to be needed (table 1). If glucose
concentrations are too high because of insulin omission,
ketosis and further hyperglycaemia can occur,40 and
perceived exercise or work effort probably increases.
Although it is unclear if there is an optimal glycaemic
range for exercise performance, clinical experience and
data from a field study in adolescents62 suggest that
maintenance of a concentration of about 6.0–8.0
mmol/L might be ideal.
Contraindications and cautions for exercise
Although few exercise restrictions should be placed on
patients, some considerations are important, and are
Elevated blood ketones (≥1.5 mmol/L) or urine ketones
(2+ or 4.0 mmol/L) [A:OK?] before a bout of exercise
should be addressed before the start of the session via
insulin administration with carbohydrate feeding if
necessary (ie, relativity euglycaemic but ketotic; see
panel 1). [A:OK?] The cause of elevated ketone
concentrations should be identified (illness, diet
manipulation, a recent bout of prolonged exercise,
insulin omission, etc). Prolonged endurance type
activities (eg, marathons and trekking) and diets very
low in carbohydrate can elevate blood ketone concentrations
in patients and blood glucose might not be
markedly elevated. The health-care professional should
therefore define appropriate protocols for ketone
monitoring and strategies for what to do when blood or
urine ketones are elevated. Blood ketone concentrations
of 3.0 mmol/L or more should be managed immediately
by a qualified health-care professional (eg, a hospital
emergency department or physician).
Severe hypoglycaemia (defined here as blood glucose
≤2.8 mmol/L or a hypoglycaemic event requiring
assistance from another individual) within the previous
24 h is a contraindication to exercise, because of
the substantially increased risk of a more serious
episode during exercise.63 In situations where minor
hypoglycaemia (blood glucose 2.9–3.9 mmol/L, with the
ability to self-treat) has occurred, the increased risk of
recurrence must be taken into account.64 Vigilance
around monitoring should be stressed and exercise
should be avoided if the setting is deemed particularly
unsafe (eg, Alpine skiing, rock climbing, swimming or
Overall, the health benefits of being physically active
outweigh the risks of being sedentary for people with
diabetes. Those with complications can derive several
health benefits from low intensity physical activities,
with little risk of any adverse events.65 In individuals with
long-standing disease or with HbA1c concentrations well
above the target, vigorous exercise, activities involving
lifting of heavy weights, and competitive endurance
events are contraindicated, particularly if the patient has
unstable proliferative retinopathy, severe autonomic
dysfunction, or renal failure.65
Inadequate preparation for exercise-associated
In preparation for exercise, individuals with type 1
diabetes should be aware of their starting glucose
concentrations, and should also have blood glucose
monitoring equipment and snacks to treat hypoglycaemia.
They should also be advised to wear or carry some form
of diabetes identification.
Goals for nutritional management
Nutritional management for people with type 1 diabetes
should incorporate strategies that optimise glycaemic
control while promoting long-term health.66 The main
strategies around nutrition for exercise and sport
discussed in this section primarily aim to maximise
athletic performance and are based largely on studies
done in highly trained healthy individuals without
diabetes,59 with few studies done in people with type 1
diabetes. Application of these strategies to people with
type 1 diabetes must consider the individual’s insulin
management plan and include specific advice focused on
nutrition for both athletic performance and glycaemic
management. A registered dietitian with specialist
diabetes and sports knowledge is the most qualified to
help active people with type 1 diabetes.
An individualised meal planning approach is central to
improvement of performance and glycaemic outcomes.
Daily carbohydrate intake should relate to the fuel cost of
training in the athletic subpopulation and ensure
prevention of hypoglycaemia for all active people.
Balancing insulin dose to carbohydrate intake during
exercise is essential. Various carbohydrate and insulin
adjustment strategies can be used, such as reduction of
the pre-exercise bolus insulin dose by 30–50% up to
90 min before aerobic exercise,67 consumption of
carbohydrates with a high glycaemic index during sport
(30–60 g/h), or replacement of carbohydrates after
anaerobic exercise. Personal tolerance of ingested
carbohydrate, particularly during exercise, is a key factor
in tailoring of recommendations. The distribution of
macronutrient intake over the day should take into
account the timing of exercise so that liver and muscle
glycogen stores are maximised before the activity and
replenished in early recovery.59 This strategy should
include carbohydrate feeding well before exercise (~4 h)
and early in recovery.59,68Daily energy and macronutrient balance
Athletes with type 1 diabetes need sufficient energy to
meet the demands of their daily activities. These
demands will vary with age, sex, body composition, and
activity type.69 Total energy requirements differ with
individual aims. Predictive equations can be used to
estimate resting energy expenditure;70 however, they
should serve only as a guide, as they could overestimate
or underestimate actual requirements. An appropriate
macronutrient balance and micronutrient intake,59
coupled with a glycaemic control strategy, is required to
maximise performance. The optimal macronutrient
distribution will vary depending on the individualised
assessment and exercise goals. A guide to the nutritional
distribution of the total daily energy intake is as follows:
45–65% carbohydrate, 20–35% fat, and 10–35% protein,
with higher protein intakes indicated for individuals
wanting to lose weight.71
The major nutrients required to fuel performance are
carbohydrates and lipids, while the addition of protein is
needed to help foster recovery and maintain nitrogen
balance.59,72 Protein requirements range from 1.2 to 1.6 g
per kg body weight per day, and will vary with training
type and intensity, and carbohydrate availability.59,73
Higher intakes might be needed for recovery from injury
or for individuals on energy-restricted diets74 to maintain
lean body mass.
Carbohydrate needs before, during, and after exercise
A distinction should be made between carbohydrate
needs for performance and carbohydrate intake required
for hypoglycaemia prevention (table 1). Carbohydrate
requirements will alter insulin management strategies
and vice versa. Most studies in type 1 diabetes have
investigated the amount and distribution of carbohydrate
required to prevent hypoglycaemia rather than to
optimise performance, although the two might be at
least partially related.34,67,75,76 For example, although only
15–20 g/h of carbohydrate might be required to prevent
hypoglycaemia in people who reduce their insulin
concentrations in anticipation of exercise, this amount of
carbohydrate could be insufficient for performance.
Implementation of increased carbohydrate supplementation
(up to 75 g/h) is possible for prolonged activity
lasting longer than 2.5 hours (eg, marathons and other
endurance type races) without having an adverse effect
on glycaemia, as long as the insulin dose is titrated
appropriately.55 In general, carbohydrate requirements
during shorter, intermittent, high-intensity, and
anaerobic activities can be considerably decreased
Nutritional needs for recovery
Nutrition requirements to maximise muscle recovery
and muscle protein synthesis after exercise have been
well studied in the athletic population without diabetes.77
For replenishment of glycogen content after exercise,
carbohydrate intake is essential.59 For athletes with type 1
diabetes, rapid and adequate replenishment of muscle
and liver glycogen stores is essential to help prevent late
onset hypoglycaemia. Glycogen replacement strategies
could also be important in prevention of euglycaemic
ketosis in exercise recovery.78 Ingestion of protein
(~20–30 g) in addition to carbohydrate in the period after
exercise is beneficial for muscle protein synthesis, but
protein ingestion does not appear to facilitate glycogen
replenishment in athletes who do not have diabetes.59
Role of high and low glycaemic index foods for
maintenance of euglycaemia
The glycaemic index of a carbohydrate-rich food can be
used to assist with the selection of the carbohydrate type for
exercise; sports drinks and energy gels with a high
glycaemic index provide rapidly released carbohydrate to
increase blood glucose concentrations during endurance
events and can treat or prevent hypoglycaemia.
Consumption of foods with a low glycaemic index before
exercise could sustain carbohydrate availability and
maintain euglycaemia, whereas consumption of meals and
snacks with a high glycaemic index after exercise could
enhance recovery. Snacks with a low or moderate glycaemic
index could also be preferred for long-distance activities
such as trekking and long-distance cycling at low to
moderate workloads. Consumption of a carbohydrate with
a low glycaemic index (isomaltose) 2 hours before a high
intensity run in adults with type 1 diabetes showed better
blood glucose responses during exercise than did
consumption of a carbohydrate with a high glycaemic
index (dextrose).79 In adults with type 1 diabetes,
consumption of a meal and bedtime snack with a low
glycaemic index after midday exercise prevented
postprandial hyperglycaemia more effectively than
consumption of a meal and snack with a high glycaemic
index after exercise, with both meal types being protective
against hypoglycaemia for about 8 h.80 [A: OK as edited?]
The protection provided by a snack was not sustained
beyond 8 h, and the risk of hypoglycaemia remained high
for at least 24 h.80
Adequate fluid intake before, during, and after exercise is
necessary for prevention of dehydration and optimisation
of performance.68 Water is the most effective drink for
low-intensity and short-duration sports (ie, ≤45 min), as
long as glucose concentrations are 7 mmol/L or higher.
Sports beverages containing carbohydrate (6–8%) and
electrolytes are useful for athletes with type 1 diabetes
exercising for a longer duration; they are also useful as a
hydration and fuel source for higher intensity exercise,
and for prevention of hypoglycaemia.34,81 However,
overconsumption of these beverages can result in
hyperglycaemia. Milk-based drinks containing carbohydrate
and protein can assist with recovery after exercise
and prevent delayed hypoglycaemia.76Low-carbohydrate high-fat diets and exercise
People with type 1 diabetes can choose a low carbohydrate
high fat diet for various reasons. A review on low
carbohydrate high fat diets and sports performance in
individuals without type 1 diabetes concluded that,
despite increasing the ability of muscles to utilise fat over
time, no evidence was available to suggest performance
benefits.82 Long-term studies have yet to be done on the
health, glycaemia, or performance effects of low
carbohydrate high fat diets in people with type 1 diabetes.
A concern with these diets is that they could impair the
capacity for high-intensity exercise.83
Variation in carbohydrate intake (ie, periodisation
throughout the training cycle according to fuel needs and
performance) has been suggested by some researchers as a
way to help promote adaptation of skeletal muscle
to training.84 Additionally, various exercise-nutrient
protocols are used to manipulate carbohydrate availability,
such as training in a fasting state or withholding
carbohydrate intake at a meal before or after exercise. These
approaches have not been studied in individuals with type 1
diabetes, in whom manipulation of dietary carbohydrate as
part of training presents unique challenges for insulin
therapy and requires careful glucose monitoring.
Sports nutritional aids and type 1 diabetes
The use of ergogenic aids is a widespread performance
enhancement strategy used by athletes, but little evidence
is available on their use in athletes with type 1 diabetes.
Caffeine intake in athletes without diabetes has shown
improvements in endurance capacity and power output.85
Caffeine intake (5–6 mg per kg body mass) before
exercise attenuates decrease in glycaemia during exercise
in individuals with type 1 diabetes, but it might increase
the risk of late onset hypoglycaemia.86
Recommendations for management of glycaemia
Blood glucose responses to the various forms and
intensities of exercise show high variability between and
within individuals (figure 1). Glycaemic management is
therefore based on frequent glucose monitoring,
adjustments to both basal and bolus insulin dosing, and
consumption of carbohydrates during and after exercise.
These recommendations are intended to serve as a
starting point for insulin adjustments and carbohydrate
intake that can then be individualised (figure 2).
Clinical management strategies should be built
around exercise types and individual aims, and
implementation of these strategies should take into
account the factors summarised in panel 2. Generally,
sustained aerobic exercise requires more substantial
reductions in insulin dose and a higher carbohydrate
intake than a short-term high intensity interval training
session. By contrast, brief anaerobic exercise (eg,
sprinting or weight lifting) could require increased
insulin delivery, which is typically given in early
recovery rather than before exercise for obvious safety
reasons.49 Strategies for insulin dose adjustments and
carbohydrate intake during and after planned exercise
are presented in table 2 and table 3.
Insulin adjustment for prolonged activities: bolus
Reductions in the bolus insulin dose accompanying the
meal before exercise or consumption of additional
carbohydrate during exercise are typically needed to avoid
hypoglycaemia during prolonged exercise (>30 min).34,56,67,102–
104 Bolus dose reductions require planning in advance and
are probably only appropriate for exercise with a predictable
intensity performed within 2–3 h after a meal. As shown in
table 3, the extent of a mealtime dose reduction is
proportional to both the intensity and duration of the
physical activity. This approach is safe and effective; even
reducing the bolus insulin dose by as much as 75% does
not appear to increase ketone production during exercise.104
Another strategy is to combine a 75% reduction of the
bolus insulin dose before exercise with ingestion of a
snack or meal with a low glycaemic index.105 This method
also reduces the risk of hyperglycaemia before exercise.
However, this approach will not protect against
hypoglycaemia if the exercise is performed an hour or
more after consumption of the snack.105 As such, this
combined approach might be preferable only for
postprandial exercise done soon after a meal.
Basal insulin approaches
Late postprandial hypoglycaemia (>4 h after a meal)
following aerobic exercise is driven partly by circulating
basal insulin concentrations. Elevated insulin sensitivity
after exercise, and possibly a blunting of glucose
counter-regulation, appear to place individuals at risk for
at least 12 h. Reduction of circulating basal insulin
concentrations can ameliorate this risk. For patients on
multiple daily insulin injections, clinical observations
and limited experimental data106 show that reduction of
long-acting basal (as well as prandial) insulin
concentrations before exercise reduces the risk of
hypoglycaemia during and after the activity, but might
promote hyperglycaemia at other points during the day.
Therefore, reduction in the basal insulin dose for patients
on multiple daily insulin injections should not be
routinely recommended but can be a therapeutic option
for those engaging in considerably more planned activity
than usual (eg, camps or tournaments). In general, basal
insulins with a short half-life, such as NPH insulin or
insulin detemir, seem to lead to less hypoglycaemia in
conjunction with exercise than do basal insulins with a
longer half-life, such as insulin glargine,107 although the
mechanism through which this occurs is unclear.
Although ultra-long-acting insulins (eg, insulin degludec,
with a 25 h half-life) pose similar risks of hypoglycaemia
with endurance exercise to those of insulin glargine,108
dose reductions for exercise would have to be
implemented at least 48 h before planned exercise. We do
not recommend this, as it would compromise overall
Continuous subcutaneous insulin infusion offers the
flexibility to modify basal infusion delivery and obtain a
quick effect (within ~1–2 h).109 Suspension of basal insulin
infusion at the onset of 60 min exercise reduces the risk
of hypoglycaemia during the activity, but it could increase
the risk of hyperglycaemia after exercise.110 Moreover,
glucose concentrations could still decrease by 2–3 mmol/L
over 30–60 min even when basal insulin is dramatically
reduced (or completely suspended),67,110,111 because of the
lag time in the change in circulating insulin
concentrations. Where practical, a basal rate reduction,
rather than suspension, should be attempted 60–90 min
before the start of exercise. An 80% basal reduction at the
onset of exercise helps mitigate hyperglycaemia after
exercise more effectively than does basal insulin
suspension, and appears to be associated with a reducedrisk of hypoglycaemia both during and after the activity.67
However, the optimal timing of basal rate reductions for
aerobic and high intensity exercise activities and the
maximal safe duration for insulin pump suspension have
yet to be determined and remain open to debate. To limit
the risk of compromised glycaemic control and ketosis,
we propose a time limit of less than 2 h on the basis of
rapid-acting insulin pharmacokinetics.109
Hyperglycaemia commonly occurs in patients after
intense exercise, particularly if insulin concentrations
are reduced. Continuous subcutaneous insulin infusion
seems to offer advantages over multiple daily insulin
injections in the management of early onset112 and late
onset hypoglycaemia after exercise,113 because of the
increased flexibility around basal insulin adjustments.
Overcorrection of hyperglycaemia after exercise via
repeated insulin dose administration results in an
increased risk of severe late onset hypoglycaemia, which
could even be fatal.50
Strategies to reduce the risk of late onset
hypoglycaemia after exercise
Increased insulin sensitivity lasts up to 24–48 h following
exercise.47 Few studies have tested various nutrient or
insulin dose adjustments to prevent hypoglycaemia after
exercise. Nocturnal hypoglycaemia after exercise
commonly occurs in individuals with type 1 diabetes,114
with an increased risk after afternoon exercise.48,115
Immediate increases in insulin sensitivity after exercise
can be addressed through a reduction of about 50% in
the bolus insulin dose administered at meal after
exercise, along with consumption of a snack with a low
glycaemic index at bedtime.80 In one study of 16 young
people using an insulin pump, a temporary basal rate
reduction of about 20% at bedtime for 6 h reduced the
risk of nocturnal hypoglycaemia.113 Similarly, in another
study of ten men on multiple daily insulin injections, a
20% basal rate reduction on the day of exercise along
with provision of a free carbohydrate snack at bedtime
(0.4 g carbohydrate per kg body mass) reduced the risk
of nocturnal hypoglycaemia.106 Individuals at high risk ofsevere nocturnal hypoglycaemia (eg, those with
recurrent hypoglycaemia and those sleeping alone)
should take additional preventive measures, including
blood glucose checks at 0200 h or 0300 h, or the use of a
real time continuous glucose monitoring system with
alarms and automatic pump suspension.116 Consumption
of a snack alone, without changing basal insulin therapy,
does not appear to entirely eliminate the risk of nocturnal
hypoglycaemia,80 and alcohol intake might increase
Emerging tools for exercise management
Several treatment regimens exist for people with type 1
diabetes. Continuous subcutaneous insulin infusion
offers better flexibility in basal insulin adjustments and
management of exercise-associated hyperglycaemia than
other methods of insulin delivery.117 Continuous
subcutaneous insulin infusion is associated with reduced
hyperglycaemia after exercise compared with multiple
daily insulin injections,112 but can create frustrating
challenges for sports that might require disconnection of
the insulin pump (for example, combat sports, diving,
and some team sports such as football, soccer, field
hockey, or basketball).118 Continuous subcutaneous
insulin infusion could also contribute to a greater sense
of being diseased and social stigma in some individuals
by drawing undue attention to their condition.118
Prolonged disconnection of the pump (>60 min) should
be managed by reconnecting, testing, and reconnection
of the pump if necessary, or by switching to basal insulin
provision by needle. Continuous glucose monitoring
provides comprehensive information on blood glucose
concentrations, real-time trends, and rates of change,
which can be used to prevent low concentrations during
exercise,119 even in unique settings where self-monitoring
of blood glucose is difficult.120 Existing sensors are
reasonably accurate for exercise;96,121 however, the lag time
in glucose equilibrium with the interstitial space and the
rapid turnover in glucose during exercise might affect
accuracy (ie, overestimate blood glucose when
concentrations are dropping and underestimate it when
concentrations are rising).97,122
Structured educational sessions can be implemented
by downloading data on self-monitoring of blood glucose,
continuous glucose monitoring, and continuous subcutaneous
insulin infusion.123 Continues glucose
monitoring systems now offer the option to add followers
who can view glucose concentrations in real time and
potentially alert the patient while they are playing sports.
Threshold suspension of insulin delivery in continuous
subcutaneous insulin infusion could offer additional
protection against exercise-associated hypoglycaemia,
according to some data.124 The development of a fully
artificial pancreas for exercise remains an elusive goal.125
Regular physical activity should be a routine objective for
patients with type 1 diabetes, for various health and
fitness reasons. Considerable challenges remain for
people with type 1 diabetes, and their health-care team, in
management of exercise and sports. Several small
observational studies and a few clinical trials have been
published to date that help to inform the consensus
recommendations presented here. More studies are
needed to determine how to best prevent exerciseassociated
hypoglycaemia with basal rate insulin dose
adjustments and how to manage glycaemia in the
recovery period after exercise. In general, aerobic exercise
is associated with reductions in glycaemia, whereas
anaerobic exercise might be associated with a transient
increase in glucose concentrations. Both forms of
exercise can cause delayed-onset hypoglycaemia in
recovery. A sound understanding of the physiology of
different forms of exercise and the variables that can
influence glycaemia during exercise and sport should
underpin the implementation of safe and effective
glycaemic management strategies. For aerobic exercise,
reductions in insulin administration before the activity
(ie, reductions in basal or bolus insulin, or both) can help
ameliorate the risk of hypoglycaemia, as can increasing
carbohydrate intake to 60 g per h or more. For anaerobic
exercise, conservative insulin dose corrections might be
required, although this too might increase the risk of
nocturnal hypoglycaemia, particularly if the exercise is
performed late in the day. In all instances, additional
vigilance around glucose monitoring is needed before,
during, and after the physical activity.
Panel 1: Blood glucose concentrations before exercise commencement and
recommended glucose management strategies
The carbohydrate intakes shown here aim to stabilise glycaemia at the start of exercise.
Blood glucose at the start of exercise must also be viewed within a wider context. Factors
to consider include directional trends in glucose and insulin concentrations, patient
safety, and individual patient preferences based on experience. Carbohydrate intake will
need to be higher if circulating insulin concentrations are high at the onset of exercise.
Starting glycaemia below target (<5 mmol/L)
Ingest 10–20 g of glucose before starting exercise Delay exercise until blood glucose is more than 5 mmol/L (90 mg/dL) and monitor
closely for hypoglycaemia
Starting glycaemia near target (5–6·9 mmol/L)
Ingest 10 g of glucose before starting aerobic exercise Anaerobic exercise and high intensity interval training sessions can be started
Starting glycaemia at target levels (7–10 mmol/L)
Aerobic exercise can be started Anaerobic exercise and high intensity interval training sessions can be started but
glucose concentrations could rise
Starting glycaemia slightly above target (10·1–15·0 mmol/L)
Aerobic exercise can be started Anaerobic exercise can be started but glucose concentrations could rise
Starting glycaemia above target (>15 mmol/L)
If the hyperglycaemia is unexplained (not associated with a recent meal), check blood
ketones. If ketones are modestly elevated (up to 1·4 mmol/L), exercise should be
restricted to a light intensity for only a brief duration (<30 min) and a small corrective
insulin dose might be needed before starting exercise. If blood ketones are elevated
(≥1·5 mmol/L), exercise is contraindicated and glucose management should be
initiated rapidly as per the advice of the health-care professional team.
Mild to moderate aerobic exercise can be started if blood ketones are low (<0·6 mmol/L)
or the urine ketone dipstick is less than 2+ (or <4·0 mmol/L). [A: OK as edited?] Blood
glucose concentrations should be monitored during exercise to help detect whether
glucose concentrations increase further. Intense exercise should be initiated only with
caution as it could promote further hyperglycaemia
1Panel 2: Factors that to consider before adjustments are made for exercise in
individuals with type 1 diabetes
Subcutaneous insulin injection and its adjustments
Differences in the site and depth of insulin injection affect absorption characteristics87,88 Lipodystrophy can lead to increased fluctuation in blood glucose and unpredictable
Inadequate understanding of insulin pharmacokinetics often leads to inappropriate
insulin adjustments, including excessive insulin corrections (stacking), which could be
particularly dangerous after exercise
Rapid acting,30 regular, and intermediate acting,89,90 but probably not long acting,91
insulin absorption rates are increased with exercise
Variation in carbohydrate quantity (including inaccuracy in measurement of intake)
and type will affect glycaemic excursions92
Self-monitoring of capillary blood glucose and continuous glucose monitoring
Errors in self-monitored blood glucose sampling or measurement errors during
self-monitoring or continuous glucose monitoring could result in inappropriate
insulin dose estimations93,94
Although the accuracy of continuous glucose monitoring is improving, it can be
compromised by poor accuracy in self-monitoring and calibrations methods95
The lag time in continuous glucose monitoring could affect accuracy during exercise96,97
Medications and alcohol
Insulin sensitivity might be affected98 as might glucose monitoring tools94
Diurnal endocrine variation, the menstrual cycle, and pregnancy affect insulin
sensitivity and glycaemic patterns99
Changes in work and sleep patterns
Such changes require adjustments in timing of basal insulin dose administration The timing of exercise should be considered relative to insulin sensitivity and the risk
of nocturnal hypoglycaemia48
Intercurrent illness and stress
Intercurrent illness or stress might necessitate changes in both basal and bolus insulin
Vigorous exercise is contraindicated
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