When I find my 5k/10k PR on the PaceWheel, it doesn’t match the times for half-marathon or marathon. Why not?
Current Fitness values are a reflection of your training for a particular race. If you ran a 5k in just under 19 minutes, you could expect to run 10k under 40 minutes with little adaptation of training; however, to run a 90-minute half-marathon or 3-hour marathon with no change in training (incorporating long runs, etc.) simply is not realistic.
