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Anatomy and physiology

In order to assist with regards to physical activity, it is important to have some knowledge of the physiological changes as a result of activity. Prolonged periods of rest will cause the body to become deconditioned, resulting in a decrease in maximum oxygen consumption, cardiac output and muscle mass. All of this compromises fitness and exercise tolerance, which can result in a negative impact on function.

Increasing the levels of physical activity or doing exercise training can lead to positive physiological changes in both the cardiovascular system and the body musculature over time (changes can be measured within 10–12 weeks).

Physiological changes of exercise

Aerobic exercise will lead to increased efficiency of the:

cardiovascular system
respiratory system
metabolic rate
lymphatic system.

Weight‐bearing exercise will also increase bone density (Winters‐Stone et al. [289]). Patients who are risk of metastatic bone disease should still be encouraged to be physically active. However new onset bone pain or pain that has changed in nature or intensity should always be investigated for fracture risk (Macmillan [289]).

Muscle‐strengthening exercise will lead to an improvement in the muscles’ ability to use energy due to:

increased levels of oxidative enzymes in the muscles
increased mitochondrial density and size
increase in number of capillary vessels within the mucsles allowing them to work more efficiently.

Endurance

This term relates to the ability of the body to carry out an exercise over time, whether it is a specific muscle contraction or cardiovascular endurance. Regular physical activity can also assist in building up endurance.

Measuring fitness

Exercise can be measured by looking at three main components: the frequency, intensity and duration of carrying out physical activity (Saxton and Daley [247]). Measuring these three components will help to determine the activity level of the individual. More specific measurements can be taken to look at specific cardiovascular fitness indicators such as VO₂ max. The most accurate way of measuring VO₂ max is by using a treadmill or a specially designed calibrated cycle. This is known as cardio‐pulmonary exercise testing or CPET.

VO₂ max (maximum oxygen consumption during exercise)

Fitness levels are often described on the basis of energy expenditure used during activity.

VO₂ max is a common method of assessing the level of energy used and measuring fitness. VO₂ max is the measurement of the maximum amount of oxygen that an individual can utilize during intense, or maximal exercise. It is measured as millilitres of oxygen used in one minute per kilogram of body weight (mL/kg/min) (Quinn [232])