Exercise, medical technology and ethicsEdexcel A-Level Biology A: Revision notes

Regular physical activity reduces the risk of several conditions. A lack of exercise is linked to:

• Obesity: less energy is used, so excess energy is stored as fat.
• Cardiovascular disease (CVD): raised blood pressure and cholesterol, and atherosclerosis.
• Type 2 diabetes: body cells become less sensitive to insulin.

Data often come from large cohort studies comparing activity levels with disease rates.

Excessive, intense or repeated exercise can cause harm.

• Wear and tear on joints: repeated impact damages cartilage, which can lead to osteoarthritis.
• Suppression of the immune system: prolonged intense exercise is followed by more infections, such as upper respiratory tract infections, in the following weeks.

Moderate regular exercise is generally beneficial; the risks apply to extreme levels.

A correlation is a relationship between two variables. A causal relationship means a change in one variable causes the change in the other.

A correlation does not prove causation, because confounding variables (such as diet or age) may differ between groups. To support causation: control or match confounding variables, use large samples, run repeated studies, use controlled trials, and identify a plausible mechanism.

Worked example: 5.0 % of an active group develop a disease, and an inactive group is 2.4 times more likely: 5.0 × 2.4 = 12 %.

In keyhole surgery (arthroscopy), a camera (arthroscope) and thin instruments are inserted through small incisions. The surgeon views the joint on a screen.

Advantages: less tissue damage, less blood loss and scarring, lower risk of infection, shorter hospital stay and faster recovery, so athletes can return to sport sooner. Disadvantages: costly equipment, highly trained surgeons needed, and not suitable for every injury.

A prosthesis is an artificial replacement for a body part. Examples: replacement hip and knee joints, and carbon-fibre running blades for people with amputations.

They restore function, so people with injuries and disabilities can take part in sport and other activities. Limitations: they can wear, loosen or become infected, they are costly and need replacing, and there are debates over whether advanced prostheses could give an unfair advantage.

Performance-enhancing substances include anabolic steroids (increase muscle growth) and EPO (increases red blood cell production, so more oxygen is delivered). Ethical positions:

• Against: unfair advantage (cheating); health risks such as heart disease, liver damage and clotting; pressure on clean athletes and young people; role-model effect.
• For: if all are allowed under medical supervision, the playing field is level and risks are lower; autonomy (informed adults can choose).

A strong answer weighs the arguments and gives a justified conclusion.