Nick Farr, an ultramarathon runner and head coach at P3 Fitness, organizes running feedback into three categories to help runners track whether their workouts match their intended purpose.
Performance output includes pace, speed, distance, time, elevation, cadence, stride length, and power. These metrics show what you accomplish but offer an incomplete view of effort alone.
Biological load describes how your body responds to the work. Heart rate, breathing rate, oxygen consumption, and core temperature provide context for your output. Farr says you don't need to track every marker. Start with one signal available to you, such as heart rate, and notice how it relates to your intended effort over time.
Subjective feedback is your own perception of the run, measured on a rate of perceived exertion scale from 1 to 10 or described through observations like whether you can hold a conversation during an easy run. Farr encourages newer athletes to run by perceived effort alone for a few weeks to learn how different intensities feel, then layer in metrics from the other two categories.
Farr's starting guideline is simple: if two of the three categories agree, use those two to guide your decision-making. On an easy run, if your pace matches your plan but your heart rate and effort both feel harder than expected, slowing down can bring the run closer to its goal of recovery and aerobic building. Conversely, on a cool day, if pace feels easier than planned while heart rate stays lower, you might push harder depending on the workout's purpose.
Before a run, identify the workout's purpose. During the run, check how the three categories relate to each other and consider whether environmental conditions or fatigue explain any disagreement. After the run, record what happened to create a reference for future workouts.