The early risers had their peak performances at midday, the intermediate group did best in the afternoon and the late risers did best in the evening. Everyone did the worst at 7 a.m.
Dr. Brandstaetter said some earlier studies had examined as many as 20 athletes while others had as few as six to eight.
Scientists not involved in the research said the findings make intuitive sense. “Every athlete knows that there are times of day when they perform best,” said Dr. Benjamin D. Levine, the director of the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital in Dallas.
But researchers also said that the large differences in performance that the study found needed to be replicated. Dr. Levine said future studies should also involve larger groups of elite athletes and more rigorous performance tests that accurately reflect each athlete’s chosen sports.
Kenneth P. Wright Jr., the director of the sleep and chronobiology lab at the University of Colorado, Boulder, said the findings seemed consistent with what is known about biological clocks. Researchers have long known that an individual’s natural circadian rhythm controls body temperature, heart rate, reaction time and concentration, so it might be expected that individual biological clocks would affect athletic performance.