dean moriarty wrote:
How would swimming 2 hours a day hurt your running?
IT definitely depends on the athlete. I am sure it could help many runners, but hurt others. How could it hurt some? If you are not naturally very strong (good at recovering, lots if inherent endurance), and are exhausting yourself swimming, then you will be likely doing your running miles either at a much slower pace (lack of quality), or the combined running on top of the swimming will be exhausting you. Some athletes it might effect the nervous system/firing patterns of your legs, ie, the kicking motion of swimming is different than the running motion, and possibly some muscle confusion could develop, negatively effecting running stride.
Another question to ask would be: if swimming 2 hours a day can't hurt (as your question seems to suggest), then why isn't EVERY good runner doing it? Why hasn't salazar (the king of trying new training methods) implemented 2 hour swims for Webb, Ritz, and the like? And if Geb added 2 hour swims to his running training, would he be a 2:01 marathoner next year? I doubt it.
So it could help in ways, but for elites, it likely could hurt in more ways. I don't think Mottram would have won a bronze medal and run 12:55 and 3:48 if he had continued with tons of swimming on top of or in lieu of the running miles he did, do you? Or do you think he could have won the gold and run 12:48/3:46 if he had continued with 2 hour swims? And would have Webb run 3:53 in HS if he continued swimming tons in HS, instead of just focusing all his efforts on run training? The likely answer is no.
At a certain point, for athletes that can handle lots of running miles, SPECIFICITY is best. For those that can't handle lots of run miles, cross training can work by improving the overall aerobic fitness.