My Dad had a major heart attack at age 49. I’d knocked off work early that day so was at home to call the ambulance. Otherwise he likely would have died alone on the floor, or at best sustained permanent, life-changing damage. As endurance athletes, we can put a LOT of stress on our hearts. Of course this is a positive thing in good measure. Giving your heart a workout builds a strong heart! But what if there are any undiagnosed heart conditions lurking in the background? And is there a point where the sheer volume of high-stress endurance work is simply too much?