4.2.2 Response to exercise

• Explain how the body reacts to increased energy demand during exercise

  ● Increased heart rate → increased blood flow to muscles / lungs

  ● Increased breathing rate and volume → more air / oxygen enters lungs

  ● To supply more blood containing more oxygen (and glucose) to muscles

  ● For more aerobic respiration to release energy / to reduce anaerobic respiration & lactic acid build up
• What happens when muscles are supplied with insufficient oxygen?

  ● Anaerobic respiration → oxidation of glucose is incomplete

  ● Causing a buildup of lactic acid which causes:

  ○ Oxygen debt

  ○ Muscles become fatigued and stop contracting efficiently (if activity long / vigorous)
• What is oxygen debt? (HT only)

  Amount of extra oxygen the body needs after exercise to react with lactic acid and remove it from cells
• What is the role of the liver in recovering from vigorous exercise? (HT only)

  1. Blood flowing through muscles transports lactic acid to the liver

  2. Where it is converted back to glucose
• “During exercise, the heart rate of

  smokers increases more than the heart

  rate of non-smokers.”

  Design an investigation that would allow

  you to test this hypothesis. (6)

  ● Two large groups of people - non-smokers and smokers

  ● Get each person to do [named] exercise

  ● Control variables

  ○ Same type and length of exercise

  ○ Same age / gender

  ○ No health issues

  ● Record heart rate for each person before and after exercise

  ● Calculate increase in heart rate for each person after

  ● Compare results for each group