If I normally train at N bpm during a run and start doing some training on a bike, should I expect to get an equivalent session at the same HR? And would you normally experience the same perceived effort? I've read in a few places that there is supposed to be some differential of 10-15bpm (lower on the bike) which doesn't make any sense to me at all. I would say I feel very comfortable (too comfortable!) at the same HR on a bike as compared with on the run.
Surely as far as internal (cardiovascular) processes go, a hr is an hr? irrespective of my external efficiency at the different sports.