Just a little confused. I recently got "Heart Zones Cycling" and am reading through it a second time. In the beginning it explains the different elements of HR. The first line makes sense (paraphrasing) that Max HR is the max number of beats your heart can produce.
But then in the next line it starts talking about your Max being different for different sports. If that is the case then wouldn't this "max" not be your max if you could get it higher doing a different sport? If I figure out my max from one sport why do I need a different "max" for another sport.
That's because different muscle groups are involved. For example, you don't use your arms cycling so your MHR is a little lower than in running. Cyclists who have little muscle mass in their upper body tend to have lesser of a difference in their MHR's between cycling and running.