Effects of exercise

Exercise affects the circulatory system, respiratory system, and the muscles. Short term effects occur immediately as we begin to exercise. Long term effects are more concerned with adaptive changes over time with regular exercise.

Short Term Effects of Exercise

When we begin to exercise the body has to respond to the change in activity level in order to maintain a constant internal environment (homeostasis). Here are the changes which must take place within the muscles, respiratory and circulatory system:

Circulatory System

  • The release of adrenaline (often before exercise even begins) causes the heart rate to rise
  • This increases Cardiac Output
  • Venous return increases due to the higher Cardiac Output and the skeletal muscle pump and respiratory pump
  • Increases in Lactic Acid (produced during the early anaerobic phase of exercise), Carbon Dioxide (due to increased rates of energy production) and temperature all act as stimuli to the cardiac control centre which responds by further increasing the heart rate
  • Oxygen levels within the blood decrease which causes increased diffusion at the lungs
  • Blood pressure increases, thus increasing flow rate and the speed of delivery of O2 and nutrients to the working muscles
  • Vasodilation and vasoconstriction ensure blood is directed to areas that need it (muscles, lungs, heart) and away from inactive organs

Respiratory System

  • Changes in the concentration of CO2 and O2 in the blood are detected by the respiratory centre which increases the rate of breathing
  • The intercostal muscles, diaphragm and other muscle which aid the expansion of the thoracic cavity work harder to further increase the expansion during inhalation, to draw in more air.


  • The higher rate of muscle contraction depletes energy stores and so stimulates a higher rate of energy metabolism.
  • The body's energy stores are slowly depleted
  • Myoglobin releases its stored Oxygen to use in aerobic respiration. O2 can now be diffused into the muscle from the capillaries more quickly due to the decreased O2 concentration in the muscle.

Long Term Effects of Exercise

Regular exercise results in adaptations to the circulatory, respiratory and muscular systems in order to help them perform better under additional stress. Here are the changes which must take place within the muscles, respiratory system and circulatory system:

Circulatory System

  • The cardiac muscle surrounding the heart hypertrophies, resulting in thicker, stronger walls and therefore increases in heart volumes. The more blood pumped around the body per minute, the faster Oxygen is delivered to the working muscles.
  • The number of red blood cells increases, improving the bodies ability to transport Oxygen to the muscles for aerobic energy production.
  • The density of the capillary beds in the muscles and surrounding the heart and lungs increases as more branches develop. This allows more efficient gaseous exchange of Oxygen and Carbon Dioxide.
  • The resting heart rate decreases in trained individuals due to the more efficient circulatory system.
  • The accumulation of lactic acid is much lower during high-levels activity, due to the circulatory system providing more Oxygen and removing waste products faster.
  • Arterial walls become more elastic which allows greater tolerance of changes in blood pressure.

Respiratory System and Exercise


  • Increased numbers of mitochondria (the cell's powerhouse) means an increase in the rate of energy production.
  • The muscles, bones, and ligaments become stronger to cope with the additional stresses and impact put through them.
  • The amount of myoglobin within skeletal muscle increases, which allows more Oxygen to be stored within the muscle, and transported to the mitochondria.
  • Muscles are capable of storing a larger amount of glycogen for energy.
  • Enzymes involved in energy production become more concentrated and efficient to aid the speed of metabolism.

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