Exercise-related metabolism is a very finely tuned process that requires co-ordinated responses from many physiological systems. In diabetes the insulin-like effect of exercise can be beneficial as well as potentially dangerous.
Although risks associated with physical function assessment under properly supervised and controlled conditions are minimal, health care professionals and
During exercise Post exercise
Muscle activity Circulating FFA
Insulin sensitivity Blood glucose levels Catecholamines
SNS activity
or insulin secretion or adipose tissue lipolysis
or hepatic glucose production
Exercise-induced hypoglycaemia
Muscle activity
Insulin sensitivity Blood glucose levels SNS activity
or insulin secretion insulin stimulated glucose uptake
or hepatic glucose production
Post-exercise induced hyperglycaemia
1A 1B
Figure 16.1 Simplified schematic representation of exercise-induced hypoglycaemia and post-exercise-induced hyperglycaemia in type 1 diabetes and in people with long-standing insulin deficiency.
Broken arrows indicate causal relationships. In people with diabetes the hormonal and sympathetic nervous system response during exercise is impaired and therefore the overall effect on insulin levels adjustment is diminished (small arrows). This lack of coordinated response results is an imbalance between hepatic glucose production and glucose use
exercise physiologists involved with physical function assessment need to have a good understanding of exercise-related pathophysiology and knowledge of specific techniques to prevent adverse side effects.
Prevention starts with educating and advising patients on how to best control glucose levels and to learn to identify symptoms indicative of poor dia-betic control. The conduct of an effective and safe physical function assessment is built on the platform of the detailed clinical evaluation of the patient’s health status in order to estimate the risk to benefit ratio of performing physical func-tion testing. Subsequently, testing modalities and protocols should be chosen so as to best suit the patient’s clinical picture, capabilities and fitness level. If all reasonable safety steps have been taken and explained to patients then they can feel reassured and able to give their best during physical function assessment.
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INTRODUCTION
Cardiac, or more broadly cardiovascular (CV), disease provides one of the biggest challenges to exercise and health professionals in the United Kingdom and worldwide. This is primarily due to the scale of the problem as well as the diversity and complexity of the diseases. It is well known that CV diseases are the most common pathology in ‘Western’ societies accounting for 238,000 deaths in 2002 in the United Kingdom. About 50% of these deaths were due to coronary heart disease (British Heart Foundation, 2004). CV diseases consti-tute a huge medical burden to the NHS as most diseases are progressive and impose a life-long burden of intervention and treatment that require the investment of time, labour, drug therapy and other broader cost implications.
The umbrella term of CV disease is an oversimplification of an exceptionally diverse set of pathologies that is often simply represented by coronary heart disease. It should be recognised that any disease of the central or peripheral circulation is covered in such a term (e.g. coronary artery disease, chronic heart failure, as well as a host of congenital diseases). All CV diseases are complex and this chapter cannot do all of them full justice. In the current chapter we have chosen to present some basic information related to central CV diseases with the next chapter providing some insight on peripheral CV diseases.
One increasingly common intervention to aid prevention and improve treatment of CV diseases is the promotion of physical activity (Thomas et al., 2003). A structured approach when attempting to increase levels of physical activity generally begins with the assessment of aspects of CV health (structure and function) as well as the determination of an individual’s maximal or symptom limited CV performance capacity via an exercise test. The knowledge of CV health and physical performance capabilities are then used as a source of information that will shape a host of processes including risk stratification and exercise prescription. This, and the next, chapter cannot cover all variables and CHAPTER 17