I've attended classes in which the instructor asked us 'to add 15 heartbeats within this climb'. In my mind all I thought was what a dangerous statement it was. Heart rate training is a major component within the Spinning Program, and instructors need to check themselves on how to craft statements that allow students to find success within their own working parameters.
Students with Atrial Fibulation, Premature Ventricular Contractions, or those on beta blockers (among other conditions) may not have 15 heart beats to spare. Instructors must give options to their suggested class structure, and be able to give modifications for all riders. Even 'plus or minus 5 heartbeats' as a teaching cue can be a dangerous thing. Those on beta blockers may only have a 20 beat working range-period! Instead, one could suggest 'doing a little more work if you feel you have the capacity to do so'.
I've got a rider on beta blockers with a very limited heart rate range due to the medication. We are fortunate enough to have bikes that measure power, and with this ability have found his maximum aerobic efficiency threshold to be 245 watts. He now knows his warmup goal is 147 watts (60% of threshold power) and can remain aerobic close to 245 watts. That's quite a range compared to the 14 heart beats he was used to riding within before we had the ability to measure work on the bike!
The same language guidelines for teaching heart rate training apply to training with power. As instructors, we can't ask the class as a whole to 'do 20 more watts of work'. As an example, here is the difference in wattage range within zones for 2 people with different work thresholds:
Rider 1 PST of 135w, which means they warm up to Z1 of 81w, Z2 range is 81-115w. That gives this rider a range of 34w within their Z2.
Rider 2 PST of 235w, which means they warm up to Z1 of 141w. Z2 range is 141-200w. That gives this rider a range of 59w within their Z2.
I have both young and old, men and women who share the above thresholds. You can't put an age or a gender on it. The work you can do is the work YOU can do- and that is unique. Each rider can focus on improving their capacity to do work within their ranges, based on science, to reach their health, fitness or performance goals. It is our job to guide them with intelligent profiles based on physiological benefits, and using all inclusive, yet clear language to help them.