As muscle mass increases, caloric expenditure increases. Does heart rate increase as muscle mass increases to provide a means for burning all of these calories?
No, i believe it is the increase in ones metabolic rate that causes this higher calorie burn
I think this makes sense in theory. However, as you gain mass you would probably gain extra blood volume as well. With strength training, “concentric hypertrophy” of the heart muscle would probably also increase stroke volume to some degree (albeit not as much as the “eccentric hypertrophy” observed in endurance-trained athletes).
I would guess that you would need to pack on a substantial amount of muscle (15 - 20 % additional total body weight) to affect the cardiovascular dynamics enough to detect an increase in resting HR (and even then, it might not occur, for the reasons mentioned above and others).
If your HR is increased…this may be to your current training (or overtraining status), and the diet/supplements you are currently taking.
As far as max HR is concerned, I don’t think it is very trainable (which is why the age-based formulae for determining it are fairly accurate). However, I have heard that biathletes, etc., have max HR’s in the neighborhood of 230 - 250 b/min. I’m not sure whether this is genetic or a result of training adaptations.
Interesting question though…I’m not sure there is a “definitive” answer…?