The Running Efficiency Index (REI) is a metric that quantifies how efficiently you are using your heart rate during a run. It is calculated by dividing your speed by your heart rate, providing insights into the balance between pace and cardiovascular strain.
A higher REI indicates better efficiency, meaning you are maintaining a faster pace with less effort. This can be particularly useful for runners aiming to improve their performance without increasing their heart rate significantly.
Results are for informational purposes only and do not constitute professional advice.
