4 (a) Most of the energy used during exercise comes from aerobic respiration - Edexcel - GCSE Biology - Question 4 - 2018 - Paper 1

To calculate the heart rate during gentle exercise, we can use the formula for cardiac output:

$\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}$

In this instance, we have:

• Cardiac Output during gentle exercise = 15.6 dm³/min
• Stroke Volume during gentle exercise = 0.13 dm³

Substituting the known values into the formula gives us:

$15.6 = 0.13 \times \text{Heart Rate}$

To find the heart rate, we rearrange the formula:

$\text{Heart Rate} = \frac{15.6}{0.13}$

Calculating this yields:

$\text{Heart Rate} \approx 120 \text{ beats per minute}$

Thus, the heart rate of the athlete during gentle exercise is approximately 120 beats per minute.