RACERADAR
Most runners track distance: "I ran 10K today." But the real question is: how many minutes of that run were spent at the intensity that triggers the specific adaptation you need? This is exposure time — and it is arguably the most important metric in structured training.
Each workout type targets a specific physiological system. What matters is time at that stimulus:
A workout of 5 x 1000m at I-pace accumulates about 17-20 minutes at VO2max intensity. That is enough to trigger adaptation. Running a single 5K time trial would provide similar stimulus but with much more fatigue, longer recovery, and higher injury risk. Intervals are efficient exposure.
More exposure is not always better. Research shows that beyond about 15 minutes of VO2max stimulus per session, additional intervals add fatigue without proportional benefit. Similarly, tempo runs beyond 40 minutes at T-pace risk overreaching. Quality thresholds exist for each workout type.
In your training plan, each workout specifies an exposure target. When you complete and log a workout, we calculate your actual exposure time based on your pace data. This tells you whether you hit the right stimulus — independent of total distance or time.
Exposure time is the total minutes spent at the target training stimulus (threshold, VO2max, etc). It matters more than total workout distance. 20 min at T-pace beats 60 min of gray zone running.