 In a small controlled but unblinded study of 52 men, varicocele was significantly more common in equestrians than in non-equestrians.The difference between these two groups was small, however, compared to differences reported between extreme mountain bike riders and non-riders, and also between mountain bike riders and on-road bicycle riders.Horse-riding injuries to the scrotum (contusions) and testes (blunt trauma) were well known to surgeons in the 19th century and early 20th century.