Abstract: Sleep deprivation and time of day are both known to influence performance. A growing body of research has focused on how sleep and circadian rhythms impact athletic performance. This review provides a systematic overview of this research. We searched three different databases for articles on these issues and inspected relevant reference lists. In all, 113 articles met our inclusion criteria. The most robust result is that athletic performance seems to be best in the evening around the time when the core body temperature typically is at its peak. Sleep deprivation was negatively associated with performance whereas sleep extension seems to improve performance. The effects of desynchronization of circadian rhythms depend on the local time at which performance occurs. The review includes a discussion of differences regarding types of skills involved as well as methodological issues.
Alex’s Notes: I’m going to apologize in advance for the brevity of this article. I feel that this is an important topic and will be of great interest to many readers, but to be frank, the manuscript of this published ahead of print review is difficult to navigate. Basically, the authors wanted to address what effects (if any) sleep and circadian rhythms have on athletic performance. Overall, 113 studies were included for review.
Total Sleep Deprivation
Have you ever pulled an all-nighter? What about two nights? Three? Turns out that none of these impact short-term high-intensity performance. For instance, the Wingate Anaerobic Power test is used to measure peak anaerobic power and anaerobic capacity, and most commonly involves cycling madly on a cycle ergometer for 30-60 seconds. Performance on this test has been shown to be unaffected by 24, 48, and even 60 hours of sleep loss. Cycling not your thing? Well, 24 hours of sleep loss also appears to have no effect on performance on the snatch, clean and jerk, or front squat, while 60 hours of sleep loss did not decrease maximal strength and endurance of either upper or lower body muscle groups.
Things aren’t as pretty for endurance exercise. Just one night of sleep deprivation has been shown to reduce the total distance covered during treadmill walking. Results are similar with longer period of sleep deprivation. It is possible that the psychological effects (e.g. motivation) contribute to the adverse effect of sleep loss upon endurance performance. Since you are tired, you simply don’t want to continue. Conversely, the duration of anaerobic tasks is incredibly minor in comparison.
Time of Day
But let’s assume you have adequate sleep (if you don’t; now you have a goal to work towards). Are you a morning lark or a night owl? If you happen to swim, you may be interested to know that a study suggests a decrease in stroke length and an increase in stroke rate from morning to evening. Specifically, the first forward movement of the hand under water, as well as the maximal depth, was higher in the evening than in the morning, while the backward movement of the hand was unaffected by time of day. Overall, the 50-m swimming velocity was higher in the evening than in the morning and afternoon.Studies of soccer skills have reported that juggling is better in the afternoon, while chipping is more accurate in the afternoon.
Back strength has been reported to be better in the evening than in the morning, as has leg strength. Studies also reported a diurnal variation in the torque of knee extensors, with better performance in the afternoon or evening.In a study on athletes who were used to training both in the morning and evening, standing broad jump performance did not vary with time of day. Increased warm-up in the morning, which raises the body temperature to evening levels, has been found to blunt the diurnal variation in countermovement jump, and studies conducted in warm environments found no diurnal variation in jump performance.
Time to exhaustion in ergometer cycling has been found to be greater in the evening than in the morning. Evening superiority in power output and cycling time is found even in morning-type athletes who undergo a vigorous warm-up procedure before testing.
Basically, performance is better in the afternoon or evening than in the morning for nearly all kinds of sports involving both technical and physical skills. That said, a proper warmup before training has been shown to moderate this effect, making it prudent to get warm and break a light sweat before training in the morning.