I ran a marathon yesterday at age 67. It was my 7th in the past 9 years. I am in excellent health, no adverse health history, and a non-smoker. I had a full cardiovascular work-up last summer, and all the tests came back excellent. I am 5 11 and weigh about 178. I trained 5 months, but run all year long. My longest training run was 20 miles, a month before the 26-mile event. I do very well the 1st 13 miles, running at a 4:30 pace, but run out of gas the 2nd 13 miles. I got achy and had no energy, finishing at 5:25. What do need to do to have more endurance for the 2nd 13 miles? Bill Bush