Having a low heart rate is not necessarily a bad thing. Performance athletes like long-distance runners, for example, can have a resting heart rate in the low 40s and still be considered healthy.

Why Zone 2 training has become the gold standard for endurance athletes and longevity researchers, offering benefits beyond traditional high-intensity workouts.

"That's why you will often see rowers with some of the lowest resting heart rates of any athletes," Semitha said. Elite rowers have some of the lowest resting heart rates of any athletes. | Credit: ...