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

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

$$ext{Cardiac Output} = ext{Stroke Volume} imes ext{Heart Rate}$$

From the table at gentle exercise, we know:

• Stroke Volume = 0.13 dm³
• Cardiac Output = ?

We can rearrange the formula to find the heart rate:

ext{Heart Rate} = rac{ ext{Cardiac Output}}{ ext{Stroke Volume}}

Now, we need to find the cardiac output for gentle exercise. Using the value at rest:

• Cardiac Output (rest) = Stroke Volume (rest) × Heart Rate (rest)

$$ext{Cardiac Output (rest)} = 0.10 imes 68 = 6.8 ext{ dm³ per minute}$$

Now, we can find the heart rate: For gentle exercise:

• Cardiac Output = Stroke Volume × Heart Rate

Substituting in the known values:

$$ext{Cardiac Output (gentle exercise)} = 0.13 imes ext{Heart Rate}$$

We also know from the table:

• Heart Rate (gentle exercise) = Cardiac Output divided by Stroke Volume = 15.6 ext{ beats per minute}.

Thus, the heart rate of the athlete during gentle exercise is 15.6 beats per minute.