23. Physical activity, inactivity, immobilization syndrome. Factors from lifestyle and age

Physical activity

Let’s praise physical activity for a second:

  • It increases energy expenditure, contributing to maintaining healthy body mass
  • It improves the muscle/fat ratio of the body, indirectly increasing BMR
  • It decreases plasma levels of cholesterol and LDL while increasing HDL levels
  • It decreases the incidence of insulin insensitivity and diabetes
  • It improves the body’s ability for thermal adaptation – trained persons can adapt better to warm and cold environments
  • It decreases the TPR by inducing vasodilation in muscles, preventing development of primary hypertension
  • It increases bone mass and prevents development of osteoporosis
  • It decreases stress
  • It decreases the development of depression and dementia
  • It indirectly decreases the occurrence of certain cancers
  • It reduces morbidity, mortality and symptoms of heart failure and improves quality of life

It should be prescribed by doctors as part of primary care and to treat and prevent obesity, type 2 diabetes, hypertension, hypercholesterolaemia, osteoporosis, depression and dementia.

Inactivity is a global public health problem. According to the WHO are approx. 3.2 million deaths each year attributable to insufficient physical activity. It has become a problem partly due to insufficient participation in physical activity during leisure time and partly due to an increase in sedentary behaviour during work and home activities.

Immobilization syndrome

When we are ill it’s an advantage to take it slow for a couple of days by staying in bed. This is advantageous because it decreases the energy required by the cardiovascular and respiratory systems, so that the body can spend more time and energy to treat the illness. When we talk about immobilization syndrome we mean those adverse effects associated with chronic immobilization.

It used to be widely agreed that long-time bed-rest is a good thing, and that there are no adverse effects of it. 6-week complete bed-rest used to be compulsory after an AMI, for example. Research at the end of the 1990s started to show that there were no beneficial effects of keeping patients confined to their bed for so long. The trend nowadays is to get patients up and going and keeping them as mobilized as possible as soon as possible after a disease. Today the American College of Cardiology and the American Heart Association advise just 12 hours bed rest after an uncomplicated AMI.

Some patient groups are at risk for chronic immobilization:

  • Paraplegic patients
  • Neurological problems affecting the lower half of the body
    • Parkinson’s
    • Spinal cord lesion
    • ALS
    • Stroke
  • Extreme obesity
  • Late-stage heart failure
  • Severe COPD
  • Elderly

There are many adverse effects associated with chronic immobilization:

  • Long-term circulatory adaptation
  • Decubitus
  • Increased risk of pneumonia
  • Increased risk of DVT and pulmonary embolism
  • Muscle wasting
  • Obstipation
  • Osteoporosis
  • Decreased metabolic rate
  • Depression, lethargy

Let’s look at them in detail.

Circulatory adaptation: After long-term immobilization will the plasma volume decrease, haematocrit decrease and the baroreflex is impaired. This predisposes to orthostatic hypotension.

Decubitus, or pressure ulcer, is a type of necrosis that occurs when there is prolonged pressure at certain points of the skin. It commonly affects the sacral region and the heels. It’s highly associated with the inability to continuously change position during the day and night. Healthy people change position at least 50 times per night and have no risk of developing decubitus. Those that change position less than 20 times per night have 90% risk for developing it.

Faecal and urinary incontinence contribute to decubitus development. Vapor and fluid macerates the skin, and bacteria of the feces cause extra irritation and damage of the skin. Hypoproteinaemia is associated with decreased skin regeneration, which also contributes to decubitus formation.

Decubitus develops when the pressure on the skin block capillary perfusion, causing ischaemia of the tissues. If a patient lies in a bed with an angle above 30° will he slowly slide down. The shearing stress and friction caused by this further contributes to decubitus formation.

Decubitus increases the mortality rate of the patients 4 times. The ulcers are commonly infected by bacteria, which can cause osteomyelitis or sepsis. To prevent this ulcer should bed-ridden patients have their position changed every 2 hours. Faecal and urinary incontinence should be handled and cleaned appropriately. Special mattresses may decrease the pressure load.

Pneumonia frequently develops in immobilization. Ventilation is more difficult in supine position, as is coughing and mucociliary clearance. This causes mucus to accumulate in the dorsal region of the lung, which predisposes to pneumonia. This type of pneumonia is called hypostatic pneumonia. The offending agent is often nosocomial, making treatment difficult.

DVT and pulmonary embolism occurs due to stasis of venous blood in the legs and due to the haemoconcentration that occurs due to decreased plasma volume. Immobilized patients at risk for DVT may receive anticoagulants as prophylaxis.

Muscle wasting occurs with any amount of immobilization but is significant only in long-term bed rest. After 1-2 months of inactivity is the amount of muscle halved. Muscles that aren’t used are atrophied. Osteoporosis is also a consequence, as bones that aren’t used are adsorbed.

Obstipation occurs because immobilization decreases intestinal motility.

Metabolism decreases in immobilization, perhaps due to the decreased muscle mass. It may be reduced by even 20%. These patients also have decreased thermoregulation, as they have decreased ability to increase or decrease their metabolism in response to changes in environmental temperature.


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22. Energy balance. Influencing factors, pathological changes.

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24. Hypo- and hypervitaminosis, micronutrients

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