Agroup of science students has been learning how the human circulatory system reacts
during exercise. the students measured their heart rates both before and after they ran five
laps around the school gym. this was repeated two more times, with a 5-minute rest period
between each trial. the average heart rates of the students are shown in the bar graph.

 HR increases with activity and decreases when at rest. By measuring HR before and after exercise, students will be able to predict their level of cardiovascular fitness.

Explanation:

During exercise, the heart pumps at a greater frequency to supply the working muscles with blood, i.e. oxygen. After exercise, the heart does not need to pump at a high rate to supply resting muscles with the necessary oxygen.  Therefore, the HR of the students is greater during exercise and slows dramatically at rest.

Students could measure their HR at the carotid artery in the neck, on the brachial artery just under the upper arm or at the radial artery on the wrist.

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