Acute responses

• Acute responses to exercise


  Immediate, short-term responses to exercise
• Acute responses to the cardiovascular system

  1. Increased Heart Rate

  2. Increased Stroke volume

  3. Increased Cardiac output

  4. Increased blood pressure

  5. Redistribution of blood flow to working muscles

  6. Increased arteriovenous oxygen difference
• Heart Rate (HR)


  The number of times the heart beats per minute (bpm)
• Resting HR


  • Approx 60-80 bpm
• HR increases with exercise

  To increase oxygen delivery and remove waste products
• HR increases linearly with increasing exercise intensity


  Until maximal intensity is reached
• Trained athletes


  • Have a lower HR
• Stroke volume


  The amount of blood ejected from the left ventricle with each beat (ml/beat)
• Stroke volume increases with exercise

  Up to 40-60% of max capacity, then plateaus
• Stroke volume increases further


  With further increases in exercise intensity
• Resting stroke volume


  • Approx 60-80 ml/beat
• Maximal stroke volume


  • Approx 110-130 ml/beat
• Cardiac output (Q)


  The amount of blood ejected from the left ventricle per minute (L/min)
• Cardiac output increases during exercise


  Due to increases in HR and SV
• Cardiac output increases


  To increase oxygen delivery and remove waste for the working muscles
• Blood pressure


  The pressure exerted by the blood against the arterial walls
• During exercise


  80-90% of blood flow is directed to the working muscles
• During exercise


  Capillaries and arterioles expand towards the skeletal muscles (vasodilation), while blood vessels constrict towards other organs (vasoconstriction)
• Arteriovenous oxygen difference (a-vO2)


  The difference in oxygen concentration between the arterial blood and the venous blood
• At rest, the a-vO2 difference is 5 ml/100 ml of blood
• During exercise


  The a-vO2 difference increases to 15 ml/100 ml of blood
• Acute responses to the respiratory system

  1. Increased respiratory rate

  2. Increased tidal volume

  3. Increased ventilation
• Respiratory rate (RR)


  The number of breaths per minute
• Resting respiratory rate is 12-20 breaths per minute
• At the start of exercise

  Respiratory rate sharply increases
• Increase in respiratory rate


  Is triggered by increases in carbon dioxide concentrations in the blood
• Tidal volume (TV)


  The amount of air breathed in and out in one breath
• Resting tidal volume is 0.5 L per breath
• During exercise


  Tidal volume increases to 2-3 L per breath at maximal intensity
• Tidal volume


  Plateaus at higher exercise intensities
• Ventilation (V)


  The amount of air inspired and expired per minute (L/min)
• Resting ventilation is 5-6 L/min