Researchers have found that an individual’s personal circadian rhythms can affect the physiological processes that are integral to athletic performance. Based on their natural circadian rhythms, athletes were classified into either “larks”, those who rise and sleep early, “owls”, those who rise and sleep late, or intermediates. Larks and intermediates hit peak performance levels six hours after they woke up while owls peaked 11 hours after waking up (1).
Larks and intermediates have better athletic performances about 6 hours after they wake up while owls best perform 11 hours after waking up.
20 field hockey players were selected as a representative group with fitness levels and circadian rhythms matching the general population (25% larks, 50% intermediates, and 25% owls). Researchers conducted cardiovascular testing six times a day. Across individuals, there was an average performance difference of 11.2% between the lowest and highest performance. Lark and intermediate performance changes ranged from 7% to 10% whereas owl performances had an average range of 26% (1).
The larger variance in owls may explain why a majority of elite athletes are larks (2). Even a difference of 1% in performance can drastically change results. In the 2008 Beijing Olympics a 1% increase in the performance of the fourth place competitor in the men’s 100 m sprint would have resulted in a silver medal. A 1% increase in the women’s 400 m spring and 400 m freestyle would have given the fourth place a gold.
Larks, intermediates, and owls performed best at difference times of the day. However, when the data was viewed based on each individual’s biological clock rather than standardized time, larks and intermediates had nearly identical performance curves. This suggests that sleep and waking times have a relatively small effect on performance and a physiological condition controls performance (1).
A possible explanation is that larks have higher cortisol levels in the morning and more variation in cortisol levels throughout the day whereas owl have lowered cortisol levels in the morning and static cortisol levels throughout the day (3).
Sources:
1. ScienceDirect (2015). The Impact of Circadian Phenotype and Time since Awakening on Diurnal Performance in Athletes. Retrieved January 31, 2015 from http://www.sciencedirect.com/science/article/pii/S096098221401639X
2. Br. J. Sports Med. (2012). Sleep quality evaluation, chronotype, sleepiness and anxiety of Paralympic Brazilian athletes: Beijing 2008 Paralympic Games. Retrieved January 31, 2015 from http://www.sciencedirect.com/science/article/pii/S096098221401639X
3. Biol. Psychol. (1991) Morningness-eveningness and early-morning salivary cortisol levels. Retrieved January 31, 2015 from http://www.sciencedirect.com/science/article/pii/S096098221401639X