What is the length of a single cardiac cycle for a heart rate of 85 beats per minute?

To determine the length of a single cardiac cycle at a heart rate of 85 beats per minute, you can use the following formula:

Length of cardiac cycle (in seconds) = 60 seconds / heart rate (in beats per minute)

Plugging in the value:

Length of cardiac cycle = 60 seconds / 85 beats per minute = 0.7059 seconds.

To convert this value into milliseconds, multiply by 1000:

0.7059 seconds × 1000 milliseconds/second = 705.9 milliseconds.

When rounded, this gives you approximately 706 milliseconds. Therefore, the correct answer represents the accurate duration of a single cardiac cycle at this heart rate, showing how the calculation directly relates heart rate and cycle duration in terms of milliseconds.