An investigation was conducted to study the cardiovascular response to cold stimulation. The heart rates of 10 healthy participants were measured under three conditions: at rest (in a comfortable 22 °C environment), immediately before immersing their dominant hand in ice-cold water (in anticipation of the cold), and 1 minute after immersion in the ice-cold water.
The data collected is shown in the table below:
| Participant | Resting heart rate (bpm) | Heart rate immediately before immersion (bpm) | Heart rate after 1 minute of immersion (bpm) |
|---|---|---|---|
| Amit | 68 | 74 | 92 |
| Beatrice | 72 | 78 | 98 |
| Chloe | 65 | 70 | 88 |
| Daniel | 74 | 52 | 102 |
| Ethan | 70 | 76 | 94 |
| Freya | 63 | 68 | 86 |
| George | 76 | 82 | 104 |
| Hannah | 69 | 75 | 93 |
| Imogen | 71 | 77 | 96 |
| Jack | 67 | 72 | 97 |
Calculate the average (mean) heart rate for the participants 1 minute after cold-water immersion. Show your working.
Identify the participant who has an anomalous result in the data for heart rate immediately before immersion.
Suggest why most participants' heart rate immediately before immersion is higher than their resting heart rate.
State two variables that must be controlled in this experiment.
Trained cold-water swimmers and endurance athletes often have a much lower resting heart rate than the general population. Suggest why a low resting heart rate develops in these individuals.
