"...Lou Castognola, a 2:17 marathoner in 1967, was found to have a vertical jump of only 12 inches. Following the 1968 Oly Trials, he stopped training and led a rather sedentary life. Three years later we re-examined him and found that while his VO2 max had declined from 78 ml/kg to 48 ml/kg, his vertical jump had increased to 20 inches. Thus despite a lack of regular physical activity, his explosive leg strength had increased 77%." quote from The Athlete Within, Dr. David Costill
My Comment: Today I might not be able to hit 12", but the question is if Lou did drills and other exercises to improve his vertical jump when he was fit, would he have run a faster marathon? Most experts think so.