Concept
Heart rate
The number of times the heart beats each minute, used as one signal of the body's response to exercise.
What changes it
Pace, duration, heat, hills, hydration, stress, medication, illness, and fatigue can all change heart rate.
What it can show
Reliable trends can help distinguish controlled and harder work and reveal how the cost of a familiar run changes.
What it cannot show alone
A heart-rate number does not directly measure pace, fitness, recovery, or training quality without context.
How to use it
Read heart rate beside breathing, perceived effort, pace, conditions, and sensor quality.
Common misconception
A lower heart rate is not always better, and one high reading does not automatically mean the effort was wrong.