Time / min Heart rate of athlete / beats per min Heart rate of untrained student / beats per min 0 (rest) 58 74 2 (exercise) 120 150 4 (exercise) 145 178 6 ...
Question 1 Report
| Time / min | Heart rate of athlete / beats per min | Heart rate of untrained student / beats per min |
|---|---|---|
| 0 (rest) | 58 | 74 |
| 2 (exercise) | 120 | 150 |
| 4 (exercise) | 145 | 178 |
| 6 (recovery) | 90 | 140 |
| 8 (recovery) | 62 | 110 |
A student investigated the effect of exercise on heart rate. She measured the heart rate of a trained athlete and of an untrained student at rest, during two periods of exercise, and during recovery. The results are shown in the table.
(a) State the heart rate of the athlete at rest. [1]
(b) Calculate the increase in the untrained student's heart rate between 0 and 4 minutes. [1]
(c) Describe the difference in how quickly the two people's heart rates returned towards their resting values during recovery. [2]
(d) Explain why heart rate increases during exercise. [4]
(e) Explain why a lower resting heart rate can be a sign of a fitter person. [3]
(f) State one variable, other than fitness, that should be kept the same to make the comparison fair. [1]
(g) Describe how adrenaline affects the heart during exercise. [2]
Answer Details
(a) The athlete's resting heart rate is 58 beats per minute [1].
(b) Increase for the untrained student between 0 and 4 minutes \(= 178 - 74 = 104\) beats per minute [1].
(c) During recovery the athlete's heart rate fell more quickly and returned close to its resting value sooner [1] (down to 62 by 8 minutes), whereas the untrained student's heart rate stayed higher and recovered more slowly [1] (still 110 at 8 minutes).
(d) Heart rate increases during exercise because the muscles respire more and need more energy [1], so they need more oxygen and glucose delivered [1] and they produce more carbon dioxide that must be removed [1]; a faster heart rate pumps blood round faster, delivering oxygen and glucose and carrying away carbon dioxide more quickly [1].
(e) A lower resting heart rate can show a fitter person because a fit heart is larger and stronger, with a bigger stroke volume [1], so it pumps more blood with each beat [1]; therefore fewer beats per minute are needed to supply the body's needs at rest [1].
(f) One variable to keep the same (any one): age, sex, body mass, the type or intensity of exercise, or the temperature [1].
(g) During exercise adrenaline increases the heart rate [1] and increases the force of each contraction [1], so more blood is pumped to the muscles.
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