While speaking of Mahler's looks, Henry Louis de la Grange reports Alfred Roller noting Mahler's superb musculature.
So often Mahler has been thought of as intellectual and perhaps even (mistakenly!) neurotic, but his biking, swimming, hiking, and mountain-climbing actually put him in the state of a highly trained athlete. As I recall from La Grange's remarks, it was common at that time to take the sun--sunbathe--and it was during one of those afternoons in the sun that Alfred Roller observed Mahler's excellent physical condition.
Perhaps not so much the incurable endocarditis, but rather being forced to give up his fitness routines, contributed more to Mahler's decline following his daughter's death. Only a man in such fit condition could have coped with the stresses of ten years of conducting the Vienna Opera.
--John Haueisen