For many runners, an early morning jog is the perfect wake-up call, but new research suggests you may not get the full benefit until later in the day.
According to a study conducted at the University of Birmingham, early risers should wait until midday before getting their fix, while those who sleep in should leave their run until late.
Twenty professional athletes were put through their paces as part of the study, taking a fitness test no less than six times between 7am and 10pm. Each participant was also asked to fill in a questionnaire aimed at establishing which were early birds, which were night owls, and which fell somewhere in between.
Those who were up early performed much the best at around 12pm, those who rose at a reasonable but not quite so eager time excelled at 4pm, and the late-to-bed types were found to be at their peak at 8pm. In fact, the latter group's performance was 26 per cent worse if they were forced to drag themselves out of bed for an early morning run.
Roland Brandstaetter, whose research was published in the journal Cell, said: "The body clock has such a big effect because virtually every cell in the body has a clock.
"There are clocks in the brain and also in the organs, in the heart, in the liver, everything, and your physiology is controlled by these clocks. Everything happens on a day-night basis."
The team suggested the results could have particular relevance for pro athletes, where even a small change in performance could mean the difference between winning and losing, and Dr Brandstaetter even advised that football managers might take note and put the night owls on the pitch for late-starting Champions League games.
What do you think? Will you be changing your running habits in order to achieve that peak performance? Leave your comments below...