In brief:American mile record holder Steve Scott was tested for maximal aerobic capacity and running economy on three occasions over nine months, a period that included off-season, preseason, the indoor season, and the early part of the outdoor season. The laboratory results demonstrated that Scott's training raised his maximal aerobic capacity approximately 8% and improved his running economy 5%. In comparing Scott's data with that of former American record holder Jim Ryun, it appears that Scott's better economy, which allowed him to perform at a lower percentage of his maximal aerobic capacity, was the essential difference between the two runners.