OK, folks, here's a question that I've never understood the answer to and I'm sure you can help -
if my HR is higher than I'd have expected to for a known pace and I'm working in a higher heart rate zone (e.g. typically on a recovery run where I'm running in the anaerobic rather than the aerobic zone), because of: dehydration, glycogen depletion, caffeine intake, overtraining, heat or cold, headwind, hills, etc. - does that mean that I'm reaping the benefit of training in a higher heart rate zone and if not why not?