Want to know the specifics? The article is here: http://www.runnersworld.com/health/older-sprinters-bones-healthier-older-distance-runners
"Older sprinters have better bone density and neuromuscular functioning than older distance runners, according to a study published in Osteoporosis International.German researchers examined 178 competitors at the 2006 edition of the European Masters Championships. They measured bone density, lean tissue mass, and a few measures of neuromuscular functioning, or how well one's nervous system communicates with one's muscles, in three groups of athletes: sprinters, middle-distance runners and long-distance runners..."