It is the first and foremost question that comes to the mind before taking part in a marathon. Running for a marathon is completely different from running. You have to stop eating junk food, train hard and have to give up on your social life. Training hours might affect your meetings with friends or relatives. You might affect your knees while preparing for a marathon race. Long distance run damages the heart, affect arthritis and spine. Toenails too can break during a long run.