Investigating Exercise, Pulse Rate and Recovery

What pulse measurements reveal

A pulse is the rhythmic pressure change felt in an artery as the heart pumps blood. Counting these pulses gives the pulse rate, measured in beats per minute. Exercise usually increases pulse rate: working muscles need more energy from respiration, and increased blood flow helps supply the oxygen they need.

After exercise stops, pulse rate gradually returns towards its resting value. We can investigate both the increase caused by exercise and the subsequent recovery. Recovery time is the time from stopping exercise until pulse rate returns to that person’s resting rate; a shorter recovery time indicates faster recovery.

Measuring a reliable resting pulse

You need a stopwatch, a way to record results and suitable exercise equipment, such as a stationary exercise bike. A heart-rate monitor can be used instead of counting the pulse manually.

Ask the participant to sit quietly until relaxed. Place the first two fingers of one hand on the inside of the other wrist, below the base of the thumb, and press gently until the pulse can be felt. Count the beats for one minute to obtain beats per minute directly. Alternatively, count for 30 seconds and multiply by two:

$$\text{pulse rate in beats per minute} = \frac{\text{number of beats counted} \times 60}{\text{counting time in seconds}}$$

Take several resting readings. If they are reasonably stable, calculate their mean as the resting baseline. If they are still falling, allow more quiet rest before starting: a reading taken just after walking into the room may not represent a resting pulse.

A controlled exercise and recovery method

One suitable investigation compares the same person before and after a standardised period of cycling. Using the same participant reduces the influence of differences between people.

1. Record the participant’s resting pulse rate.
2. Set the exercise bike to a suitable resistance. Have the participant cycle at an agreed pace for a fixed duration selected by the teacher. Keep the pace steady, for example by monitoring revolutions per minute.
3. When exercise stops, start the recovery stopwatch immediately. Measure pulse rate as soon as possible, using a heart-rate monitor or a short, fixed counting period.
4. Continue measuring at regular intervals, such as every minute, while the participant rests in the same position. Record both the elapsed time since exercise stopped and the pulse rate.
5. Continue until pulse rate has returned to the resting baseline. Check that it remains close to that baseline with a further reading.
6. Repeat the whole trial, allowing full recovery before exercising again. Compare repeat results and calculate a mean recovery time.

Manual counting takes time, so it gives an average pulse rate over the counting period rather than an instantaneous reading. Use the same counting period each time and record consistently when each measurement begins. A monitor makes it easier to follow rapid changes immediately after exercise.

Keeping the comparison fair and safe

Keep the type, duration and intensity of exercise constant between repeat trials: use the same bike resistance and cycling pace. Also keep the pulse-measuring method, recovery posture and measurement intervals the same. These controls help ensure that differences are not simply caused by a different exercise task or measuring procedure.

If the investigation deliberately changes exercise duration, duration becomes the independent variable; keep the other conditions constant. Pulse rate and recovery time are the measured outcomes.

The teacher should assess the risks and supervise the activity. Participation must be voluntary, and anyone for whom exercise is unsuitable should not take part. Use a safe, manageable intensity rather than maximum effort. Check that equipment is secure and the surrounding area is clear. Stop immediately if a participant feels dizzy, unwell, unusually breathless or experiences pain, and tell the teacher. Never encourage someone to continue just to complete a result.

Recording and interpreting recovery

Record elapsed recovery time and pulse rate in a table, with units in the headings. Plot time since exercise stopped on the horizontal axis and pulse rate on the vertical axis. A horizontal line showing the resting baseline makes the return towards rest easier to identify.

Suppose a participant has a resting pulse of 72 beats per minute. The following constructed example shows how a recovery curve can be read.

Data for Following pulse rate back to its resting baseline

The pulse is initially above the resting baseline and then falls. In this example it reaches the baseline at four minutes, giving a recovery time of four minutes. With measurements only once a minute, the exact return could have occurred between the final two readings; more frequent measurements would give a more precise estimate.

Compare the post-exercise rate with the resting rate to describe the effect of exercise. Compare recovery times under matched conditions to describe faster or slower recovery. Differences between participants may reflect fitness, but also other factors affecting pulse rate, so one short investigation cannot establish a person’s overall health.

Practical sequence

• Rest quietly; take repeated pulse readings to establish a resting baseline.
• Exercise for a fixed duration at a controlled pace and intensity.
• Start timing when exercise stops; measure pulse immediately and at regular intervals during recovery.
• Continue until pulse returns to the resting baseline.
• Repeat trials after full recovery and calculate a mean recovery time.

Measurement and controls

$$\text{pulse rate} = \frac{\text{beats counted} \times 60}{\text{counting time in seconds}}$$