The physiological effects of drugs on the performer and their performance.

The idea

Drugs alter the body's physiology, so they change both the performer's health and their performance. Physiological effects include changes to heart rate, blood pressure, muscle protein synthesis, oxygen transport, arousal and pain perception. For example, anabolic steroids increase muscle protein synthesis, raising strength and power but risking liver damage, reduced sperm production and mood disturbance. Stimulants raise heart rate and blood pressure, delaying fatigue but risking overheating, irregular heartbeat and anxiety. Beta blockers slow heart rate, reducing tremor and anxiety but also reducing cardiac output. Diuretics reduce body mass but risk dehydration and electrolyte imbalance. The performer's performance may improve in one component while health and other components decline.

What earns the marks

• Anabolic steroids increase muscle protein synthesis, promoting muscle growth and strength gains, but can cause liver damage, reduced sperm production and mood disturbance.
• Stimulants increase heart rate, blood pressure and arousal, delaying fatigue, but can cause overheating, irregular heartbeat and anxiety.
• Beta blockers slow heart rate and reduce tremor and anxiety, but can reduce cardiac output and therefore endurance performance.
• Diuretics reduce body mass by increasing urine output, but risk dehydration and electrolyte imbalance, which impair thermoregulation and muscle function.
• Physiological effects can improve one performance component while harming health or another component, so the overall effect on the performer is not uniformly positive.

Common mistakes and how to put them right

• Misunderstanding: all drugs improve performance.

  Put it right: Some, such as beta blockers, can reduce cardiac output and endurance, so the effect depends on the drug and the performance demand.

• Misunderstanding: physiological effects are the same for every performer.

  Put it right: Effects vary with dose, individual physiology, training status and the specific sport demands.

• Misunderstanding: diuretics improve performance by reducing mass.

  Put it right: The main physiological risk is dehydration and electrolyte imbalance, which can impair thermoregulation and muscle function.

• Misunderstanding: stimulants only affect the brain.

  Put it right: Stimulants also raise heart rate and blood pressure, so they have cardiovascular as well as psychological effects.

Exam tips

• Link each drug to a named physiological mechanism and then to a specific performance component, such as strength, endurance or tremor control.
• Use comparative language, such as 'increases', 'decreases' or 'delays', to show the direction of the physiological effect.
• When a question asks about the performer and their performance, include both health effects and performance effects, not just one.