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Athletes and coaches should factor in the “body clock” when measuring performance at different times of the day.

10 Mar 2015 - 16:00

Up until now, research-based evidence suggests that humans have a “sweet spot” for physical performance in the later afternoon, or even evening. This is driven by our “body clock” which determines the time of day we prefer to wake up, eat, remember things, solve problems, lift weights and go to bed. An important thing to bear in mind, however, is that we are all a little different – my body clock may run faster than yours, such that I may prefer to do most activities earlier than you. In this study, we took into account the volunteers “preference for mornings or evenings” (we call this their chronotype – a behaviour reflective of their body clock), as well as their usual training time of day when we assessed 200m swimming time-trial performance at 06h00 and 18h00. When we compared the morning and evening performances of all the swimmers, we found they had similar morning and evening time-trial times. However, when we groups swimmers by their “chronotype” we found that the larks (morning-types) were faster in the morning time trial. Although our sample did not contain any owls (evening-types) – an interesting observation in itself – those swimmers who did not have a strong preference for mornings or evenings (called neither-types) swam faster in the evening. Taking this one step further, we regrouped the swimmers based on the time of day at which they habitually train, and found that those who train in the morning were faster in the morning time trial and vice versa.

Rae DE, Stephenson KJ, Roden LC. Factors to consider when assessing diurnal variation in sports performance: the influence of chronotype and habitual training time-of-day. European Journal of Applied Physiology. EPub ahead of print