I would say the average ultra runner is probably less hard on their body overall compared to someone training for / regularly running fast marathons (~3 hour an

I would say the average ultra runner is probably less hard on their body overall compared to someone training for / regularly running fast marathons (~3 hour and below). Both are probably running a lot of base milage at an easy pace. Marathoner is probably putting in more speed workouts, running on pavement / asphalt / concrete. Ultra runner is probably spending more time on soft surfaces and running with less repetitive motion on trails and is more likely to be doing some supplemental strength training and hiking hills. Anecdotally for me, running ultramarathons has been a net positive. The 50+ mile races themselves are probably not good for you (potentially loss of sleep, operating into and past exhaustion, running high calorie deficits while cramming mostly junk food in just to get enough sugar and electrolytes to keep moving, risk of hyponatremia or dehydration, etc.), but the training leading up to it is. Regular checkups and a visit with a cardiologist for an unrelated (genetic) condition point to me being quite healthy despite not going to a lot of effort in other areas of my life. Heart is in especially good shape.