Larks vs. owls: lessons for training and racing

Circadian rhythm and sports performance

It’s now generally accepted by sports scientists that physical and athletic performance tends to peak in the late afternoon or early evening. This is usually attributed to the daily circadian rhythm, which results in a higher body temperature, joints that are more supple, and hormone profiles that are optimized for action. However, the circadian rhythm is not exactly 24 hours, but a little over⁽¹⁾. This explains the need for external stimuli such as daylight to keep the rhythm synchronized with the 24-hour clock; remove exposure to daylight and things tend to go haywire! It’s also important to understand that within the basic and regular circadian rhythm, different people may exhibit slightly differing physiological and behavioral responses, for example, a ‘lark’ or ‘owl’ tendency (see box 1).

Box 1: Lark or owl?

The circadian rhythm does not result in identical physiological and behavioral responses in everyone. You probably know of people described as ‘larks’; getting up early and feeling sharp and in good spirits first thing in the morning seems to come naturally to these people, while they tend to wind down in the evening and retire to bed fairly early too. ‘Owls’ on the other hand are night people, who often struggle to awaken, and then feel groggy and perform poorly for hours after waking. However their mood steadily rises through the day and by the evening they’re full of energy.

Physiologists believe that these differing characteristics are primarily related to core temperature patterns, which differ between larks and owls. However, pure lark or owl behavior represents the extremes, and most of us lie somewhere in between, with a tendency towards one or the other. There is also some research indicating that pure lark or owl characteristics may not be innate, but are likely to indicate circadian ‘dysrhythmia’ – a disruption to the normal circadian rhythm⁽²⁾. Extreme owl behavior arises from delayed sleep phase syndrome (where the circadian rhythm lags behind the 24-hour day), and extreme lark behavior from advanced sleep phase syndrome (circadian rhythm becomes advanced). The current suggestion is that while we may inherit a tendency to slip into lark or owl behavior⁽³⁾, the correct circadian rhythm can be maintained with environmental clues, such as appropriate bright light exposure (more later)⁽⁴⁾.

Athletes and chronotype

When it comes to circadian rhythms, athletes are no different to non-athletes, with all of us having a particular ‘chronotype’. The term chronotype refers to an individual’s circadian preference towards morningness (lark) or eveningness (owl). Just to reiterate however, this preference lies on a spectrum, which spans extreme morningness to no particular preference through to extreme eveningness. From the descriptions of lark and owl behaviour above, you will probably already recognize if you are towards either end of this spectrum! However, if neither description seems to particularly apply to you, the chances are you are somewhere near the middle of the spectrum.

Given what we know about the role of circadian rhythm and physical performance, it’s natural to assume the following:

·        Overall, athletes will tend to perform better during the late afternoon/early evening period when they are working with their circadian rhythm and not against it – a finding that has been largely borne out in a number of previous studies^(5-8).

·        Athletes with lark tendencies will tend to perform better somewhat earlier in the day, while those with owl tendencies will fare better when asked to perform much later in the day.

But while the first assumption is supported by some good evidence, what about larks performing better in the morning, and owls better in the evening? Does this hold true in reality?

New evidence

To get a definitive answer to this question, we can turn to new research by a team of German and Austrian scientists, which was published last month in the ‘Journal of Sleep Research’⁽⁹⁾. In this study, the researchers investigated whether an athlete having a chronotype towards either end of the spectrum – ie whether they had strong tendencies towards lark or owl behaviour – really did dictate their peak performance ability. To assess performance, the researchers set out to evaluate the differences in 20km cycling time trial performance between morning and evening chronotypes. The hypothesis was that performance of evening (owl) types would be better in the evening compared with the morning, and that performance of morning (lark) types would be better in the morning.

To do this, the researchers recruited 76 competitive male cyclists and triathletes. The inclusion criteria were as follows:

·        Healthy males, 18–30 years old.

·        At least two years of cycling competition experience.

·        Injury-free with no diagnosed sleep disorders.

·        Had not completed shift work or travelled outside their local time-zone in the past month.

·        Participants had to have habitual sleep patterns where they retired between 22:00–23:30 and rose at 06:00–07:30 .

The next step was to determine the nature of the athletes’ internal body clocks – ie their circadian rhythm tendencies.

To achieve this, the researchers screened all these athletes using the ‘Morningness-Eveningness’ Questionnaire (MEQ). This tool categorizes people into morningness/eveningness based on their natural sleep-wake preferences. NB: you can see what is involved in this questionnaire and take the test to assess your own lark/owl tendency by following this Medscape link. From this larger group of 76 athletes, the researchers selected only the definite extremes for the final testing pool:

·        Ten definite morning types (M-Types) – ie athletes who naturally woke up early and felt most alert in the first half of the day.

·        Seven definite evening types (E-Types) – ie athletes who naturally stayed up late and struggled with morning alertness.

How they tested

The researchers then took the 17 athletes with very strong morning or evening tendencies and got them to ride four different 20-km cycling time trials on a cycling ergometer. The four trials were conducted on four separate days and were identical apart from the time of day when the time trial was performed. These times were as follows:

·        06:00 (6am)

·        12:00 (noon)

·        18:00 (6pm)

·        22:00 (10pm)

The order of trials for each athlete was chosen randomly to ensure there were no ‘learning effects’ carried over from one trial to another, which could have biased the results. On each occasion, the athletes were asked to ride the trial as fast as possible; visual feedback on the distance covered, power, pedaling cadence and heart rate was available during all trials. The same range of electronic gear ratios was used for each trial, and the athletes were permitted to adjust this throughout the trial to achieve their preferred cadence. All trials were supervised by the same experimenter, with standardized verbal encouragement provided during the last split in each trial.

During the trials, as much water as desired was available, and the athletes were instructed to replicate their training load and nutrition (including caffeine) from the first trial as closely as possible before each of the other trials (controlled and verified by means of written training diaries). This was to minimize the possible confounding effects of different nutritional practices from one trial to another. The key parameters measured during each of the four trials were as follows:

·        Finishing time

·        Average power output

·        Average heart rate

·        Mental ‘readiness’ prior to each ride

The measured data from these parameters in each of the four trials was then collected and analyzed to see if and how morningness/eveningness affected time trial performances at different times of the day.

What they found

A number of key findings emerged. These were as follows:

·        Overall - For the 17 athletes as a whole, the late afternoon/evening performance peak effect was evident; performance was generally better in the evening than the morning, and averaged across all the athletes, times were 2.1% faster in the later sessions – thus validating the findings from previous research.

·        Evening athletes - Relative to their average performance, evening types performed MUCH better in the evening than in the morning (when comparing 06:00 vs. 18:00 - see figure 2). As such, the overall time in evening types was on average 39.9 seconds faster at 18:00 compared to 06:00. Indeed, all the evening type athletes recorded their best performance during the second half of the day (31m:54s evening vs. 32m:28s morning). In a race situation, this is a huge difference!

·        Morning athletes - Contrary to the expectation that the morning types would crash in the evening, they proved to be highly consistent across different times of the day; there was no statistically significant difference in performance between the 6am and 10pm trials (figure 2). While it’s true that 6 out of the 10 morning athletes did post their best times in the first half of the day, their later performances didn’t suffer the same catastrophic drop-off seen in the evening athletes.

·        Pacing – the evening athletes (but not the morning athletes) showed a definite pacing pattern; in all trials, they tended to start fast, dip midway through then tried to finish fast. The difference was that in the morning trials, they could lift themselves for a faster finish.

·        Mental readiness – the evening athletes reported significantly lower ‘mental readiness’ at 6am. They physically and psychologically felt unprepared to perform. The morning athletes meanwhile reported no time of day where they struggled with mental readiness.

Figure 2: Time trial performances vs. time of day for larks and owls

Practical implications for coaches and athletes

The key take-home message of this new research is that while on average, athletes can expect to perform better in the late afternoon/evening, there’s no ‘one-size-fits-all’ rule of thumb. Your best training and racing strategy will depend on your degree of lark or owl tendency. This has real practical implications for how you structure your training and prepare for a race or important event.

Let’s start with evening types (owls). If you know you have owl tendencies, the first rule of thumb is that you should avoid if scheduling your demanding training sessions for early morning if possible. Not only will you find it harder to summon up motivation, you will also be fighting against your circadian rhythm, which will dent your training quality. To maximize the training gains from your workouts, you need to schedule your harder sessions such as intervals, threshold work, strength sessions etc late afternoon or early evening (eg 4pm – 8pm) when your body is naturally primed to produce the highest power output. If you have no option but to train in the morning – for example due to work commitments – try to keep it easy-to-moderate intensity at most.

If you are more of a morning person (lark), you have a biological advantage in that you are more flexible as to when you schedule your workouts. Unlike owls, you likely find it easier and are more motivated to perform high-intensity work at all times of the day. Having said that, while your circadian rhythm allows you to perform well anytime, you will probably prefer morning training over evening sessions. However, you shouldn’t fear evening sessions if your schedule demands it.

Given that the majority of endurance events and races often start first thing in the morning, those who are owls may at this point be feeling a bit short changed; for owls, an early start means a physiological disadvantage from the word go (literally!). However, try not to be too hard on yourself. Instead, see your owl rhythm as making you a specialist, having a higher ceiling in the evening but a lower floor in the morning. A way to navigate around this is to shift your circadian rhythm forwards prior to your event by getting up 3–4 hours earlier in the event run up in order to force your body temperature to rise earlier, and overcome the sleep inertia of a late circadian rhythm. This is rather like to preparing for a race when flying east into an earlier time zone. However, the trick is to gradually move the clock forward by getting up earlier and earlier over the course of a few days – eg four days of getting up 45 minutes earlier than the previous day, which shifts your circadian rhythm three hours forward. In this respect, exposure to bright blue light (or sunlight) immediately upon waking is important in order to suppress the sleep hormone (melatonin) and signal the brain that it is ‘performance time’. (For more advice on how to achieve this, readers are recommended to read this article on jetlag and performance). Finally, natural owls will almost certainly find that strategic caffeine use is an excellent tool for helping to bridge the ‘mental readiness’ gap identified in the study, combined with the use of longer warm ups!

References

1.       J Clin Psychiatry. 2005; 66 Suppl 9:3-9; quiz 42-3

2.       American Sleep Disorders Association. International Classification of Sleep Disorders, revised: Diagnostic and Coding Manual. Rochester, Minn. 1997

3.       EMBO Rep. 2005; October; 6(10): 930–935

4.       Sleep1990; 13:354-361

5.       Eur J Appl Physiol. 2004 Jun;92(1-2):69-74

6.       Can J Sport Sci. 1992 Dec;17(4):316-9

7.       Int J Sports Med. 2004 Jan;25(1):14-19

8.       Ergonomics. 2005 Sep 15-Nov 15;48(11-14):1473-87

9.       J Sleep Res. 2025 Dec 16:e70268. doi: 10.1111/jsr.70268. Online ahead of print