Investigating Effect of Physical Activity on Heart Rate (Cambridge O Level Biology)

• It is relatively simple to investigate the effects of exercise on the body in the classroom
• Breathing rate can be measured by counting the number of breaths per minute,
  • 1 inhalation + 1 exhalation = 1 complete breath
• Heart rate can be measured by taking a pulse
• Either can be measured before and after an activity is performed and the results plotted on a bar chart
  • It is important that the time over which breathing rate and pulse rate are measured is consistent, and that individuals fully recover (rest) before starting a new activity
• Increased physical activity results in an increased heart rate and breathing rate
  • Heart rate remains high for a period of time after the physical activity has stopped, there is a gradual return to the resting heart rate

Explaining the Effect of Physical Activity on the Heart Rate

• So that sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen for increased respiration
• An increase in heart rate also allows for waste products to be removed at a faster rate
• Following exercise, the heart continues to beat faster for a while to ensure that all excess waste products are removed from muscle cells
• It is also likely that muscle cells have been respiring anaerobically during exercise and so have built up an oxygen debt
• This needs to be ‘repaid’ following exercise so the heart continues to beat faster to ensure that extra oxygen is still being delivered to muscle cells
• The extra oxygen is used to break down the lactic acid that has been built up in cells as a result of anaerobic respiration