Table 1

A summary of nine key statements for managing glycaemic control in cardiac rehabilitation participants before, during and after exercise

Guidance pointRecommendation
1More than 25% of cardiac rehabilitation8 participants will have diabetes mellitus (DM) and over 90% of these will be type 2 diabetes mellitus (T2DM). Participants should be categorised into one of three levels of observation for exercise related to dysglycaemia risk,
  1. Participants with type 1 diabetes mellitus (T1DM), have the greatest risk of exercise-related dysglycaemia (ie, hypoglycaemia or hyperglycaemia) and require the greatest level of individualised management to maintain stable glycaemic levels (+++),

  2. Participants with T2DM on insulin or insulin secretory medications are the next level of risk to warrant moderate to similar levels of observation for dysglycaemia as those with T1DM (+++), and

  3. Participants with T2DM on all other medications or managed with nutrition and lifestyle, usually require little additional observation compared with CR participants without diabetes (NR).

2Exercise should only to be contraindicated for CR participants with DM when one of the following states persists:
  1. Recent history of ‘brittle’/unstable glycaemic control (ie, four or more episodes of severe hypoglycaemia and hyperglycaemia with diabetic ketoacidosis, without obvious or apparent causes and requiring emergency response and/or hospitalisation, over the last 12 months). These individuals are typically on exogenous insulin and have a T1DM diagnosis (NR).

  2. Low glucose level (<5 mmol/L) that is not reversed by nutritional supplementation in a short period of time (<30 min) (NR).

  3. In participants with T1DM, where hyperglycaemia is >15 mmol/L and ketones >1.5 mmol/L (NR).

  4. In T2DM, where there are ketones >1.5 mmol/L (++).

3CR services should now possess glucose and ketone monitoring devices, and where the team includes practitioners skilled in taking these measures, in an equivalent standard to monitoring blood pressure, measuring ECG and providing cardiac life support (NR).
4For CR participants with DM, the value of regular physical activity is of even greater value than for those participants without DM, as it has significant influences on these two key independent and interdependent morbidities (+++).7 Unfortunately, uptake, adherence and completion of a CR programme has been found to be poorer in CR participants with DM versus those without DM (++). Participants with DM on insulin therapy are typically more fearful of glucose exertion related events (both during or for several hours after the exercise session has ended) and therefore need greater individualised attention, support and guidance to optimise management. CR programme managers therefore need to adopt strategies to overcome both the service and psychological motivation challenges of this large and increasing subgroup of CR participants (NR).
5For those participants managing their DM with insulin, the following guidance is recommended:
  1. Before exercise, prandial insulin, if administered just before the activity, should be injected into the abdomen or upper buttock. Ideally, the bolus (prandial) insulin dose should be reduced by 25% to 50% if an exercise session is within the time action period for that insulin (ie, within 2 hours of prandial insulin). Consider up to a 50% reduction to prandial insulin with next post-exercise meal and, if engaging in regular exercise, a 20% reduction to daily basal insulin dose (multiple daily injections only). For those on pump therapy, basal rates can be reduced by 50% to 80% 60 to 90 min before the onset of exercise and rates can be resumed after the exercise is done (++).

  2. Participants with less stable T1DM should be on continuous glucose monitoring and the CR team should support needs to pursue more vigilant care in working with the participant’s diabetes care team (++).

6Risk management related to chronicity, should respect that:
  1. Increased age is associated with greater risk of hypoglycaemia (+++).

  2. Over the longer term, unlike T2DM, exercise in T1DM does not typically improve glycaemic control substantively, but is associated with reduced risk for diabetes-related complications (+++).

7In all cases and to promote the value of exercise, all should be done to reverse a contraindicated state before deciding to cease the exercise opportunity. Even if it means cutting the exercise session short while waiting for glycaemia and ketones to return to acceptable levels as detailed in sections 6 and 7 of the full report. 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). Blood glucose concentrations should be monitored during exercise to help detect whether glucose concentrations increase further. Strategies for preventing hyperglycaemia or hypoglycaemia include:
  1. Lighter intensity aerobic activity (walking, light cycling, etc) for those starting in a hyperglycaemic state (++).

  2. For participants with T1DM, if glucose is >10 mmol/L, then it is recommended to perform the aerobic exercise component of the session first before the strength and/or more anaerobic type activities (+).

  3. Performing resistance-type activities before aerobic type exercise is better suited to prevent hypoglycaemia, including those starting in an euglycaemic state.

  4. For those in a lower glycaemic state (<5.0 mmol/L), nutritional supplements of simple carbohydrates of 15 to 30 g, 30 min pre-exercise plus 25 to 30 g for every additional 30 min of activity (+).

  5. Hypoglycaemia during exercise should be treated with 15 to 30 g of rapid acting carbohydrate (glucose tabs, juice, etc). Exercise can be resumed once glucose levels rise >5.0 mmol/L.

  6. For T1DM and T2DM individuals on insulin, Section 6 provides the full details of recommendations for participants in one of five pre-exercise glycaemic categories: <5 mmol/L; 5 to 6.9 mmol/L; 7 to 10 mmol/L; 10.1 to 15 mmol/L; and >15 mmol/L (NR).

8There are a number of interactions between exercise and cardiovascular and non-insulin glycaemic management medications (see table 2, Part 2).
  1. These medications do not cause a need for extra carbohydrates to be taken with exercise: Biguanides (eg, metformin) and incretin-based therapies of GLP1-RA, DPP-4 inhibitors (+).

  2. These medications do require the monitoring of blood glucose and risk of hypoglycaemia and the need for taking of extra carbohydrate: Sulphonylureas and glinides (++).

  3. A more recent medication for diabetes is the sodium-glucose cotransporter-2 (SGLT-2) inhibitor mainly prescribed for individuals with T2DM, and sometimes in T1DM under very specific circumstances. These glucose lowering agents are principally seen as an add-on therapy when metformin alone is not sufficient to reach the glycaemic target. The SGLT-2 inhibitors have shown benefits in patients with cardiovascular disease, however, ketoacidosis, has been reported in the absence of hyperglycaemia. Interactions with exercise are unknown, but recommendations already given for vigilance in monitoring of hypoglycaemic and hyperglycaemic prevention and management would seem prudent (see section 4.1, Part 2) (++).

  4. For participants prescribed beta blocking agents, DM also attenuates the heart-rate response to exertion (and similarly for oxygen uptake responses) when either exercise commences or when exercise intensity is increased. It would seem prudent for CR participants with diabetes on beta-blockers to expect a further reduction in heart rate responsiveness to any given change in exercise intensity compared with beta-blocked CR participants without diabetes (NR).

9c. The time of day (circadian effects) of exercise also influences glycaemic regulation in both T1DM and T2DM. In those who are at risk of post-exercise hypoglycaemic events, morning exercise is recommended and for those more prone to hyperglycaemia, afternoon and evening exercise (including high intensity interval training in T2DM) has been demonstrated as preferable (NR).
  • *GRADE system scores of evidence quality

  • ++++:strong recommendation based on high-quality evidence.

  • +++:moderate recommendation based on moderate-quality evidence.

  • ++:low-strength recommendation based on low-quality evidence.

  • +:very-low strength recommendation based on very-low quality evidence.

  • CR, cardiac rehabilitation; NR, not rated.