Hayflick’s limit is not the be-all and end-all of lifespan. Yes, “stressing” the body through exercise and physical labor does cause the telemers to shorten, but there really isn’t any evidence that people die because they hit Hayflick’s limit. As far as your point about stress on internal organs, I would agree with you if cardio-vascular health isn’t also cared for, or if the caloric intake was simply sloppy. But eating heart-healthy foods and keeping the organs in shape with proper exercise will actually make them last longer.