Lark vs. owl: morning or evening training for best performance and health outcomes?

Timing questions

Although peak physical performance is known to be more likely to occur in late afternoon/evening exercise, there’s still uncertainty about the best time of day to exercise when long-term health and training adaptations are the main goal. As we can see from the study above, the ideal time of day to train among the women depended on the aspect of fitness or health being measured. In the men meanwhile, there was much less morning-evening variation all round. Looking at other review studies on this topic, the results for health benefits are rather inconclusive, with some studies suggesting morning exercise and some evening exercise to be more beneficial^(12-14). 

“There’s still uncertainty about the best time of day to exercise when long-term health and training adaptations are the main goal.”

To confuse matters further, many of the studies on exercise timing and health/fitness gains have been observational in nature, looking for associations rather than causes. Once you add in the myriad of factors that can also influence outcomes – for example, someone’s habitual exercise time, their individual chronotype (are they naturally owls or larks?), sleep patterns, their food and caffeine intake patterns, environmental conditions (some people experience different circadian patterns in summer compared to winter), it becomes very difficult to make robust recommendations.

In fact, it turns out that there has not previously been any systematic meta-review to date that has investigated the influence of exercise timing on health-related outcomes. A meta-review study is one that pools and analyzes all the previous data on a topic; because it can control for all the other types of factors listed above and brings together a large amount of data, this study type provides high levels of validity, and can therefore help provide answers to complex and tricky questions! But now, a new study by a joint team of US and Swiss researchers has tried to provide a definitive answer as to whether time of training really does matter and if so, how.

New research

In this study, which was published last month in the journal ‘Sports Medicine-Open’, the researchers performed a systematic review with meta-analysis to investigate if the time of day of exercise training in intervention studies influences the degree of improvements in physical performance or health-related outcomes⁽¹⁵⁾. To do this, all the scientific databases were trawled for research papers investigating if the time of day of exercise training in influenced physical performance, physical fitness, anthropometrics, cardiovascular or metabolic outcomes. To be included in the analysis, these research papers had to meet strict criteria:

• Studies based on structured exercise interventions with a minimum of two exercise sessions per week and a minimum intervention duration of two weeks.
• Studies comparing exercise training interventions carried out at, a minimum of two different times of the day.
• Studies that implemented endurance or strength training interventions, or both. 
• Studies that only used randomized controlled trials (considered the most rigorous and robust research method of determining whether a cause-effect relation exists between an intervention and an outcome).

In all, 22 studies met the inclusion criteria (a full list of which can be found here).

What they found

When the data from these 22 studies was pooled and analyzed, the researchers were able to conclude the following:

• There was very little evidence for or against the hypothesis that exercising at a certain time of day is more beneficial than exercising at any other time of day. This finding was true whether the training was conducted to improve aspects of performance such as endurance, strength or dynamic power. It was also true when the goal of training was to improve body composition (lower body fat), or improve cardiovascular health, or metabolic markers related to cardiovascular health (eg blood lipids etc).
• There WAS some evidence for a benefit of matching the time of day of training to the time of day of testing for performance-related outcomes (see figure 1). For example, if you are training to improve jump height and the testing is being conducted in the morning, you are best training in the morning. But evening testing would require evening training for the best results.
• Because most of the included studies were quite different in the way they were designed and executed and often did not contain large numbers of participants, the researchers suggested that ideally, further studies in this area should be carried out in order to further clarify the results.

Figure 1: Training time of day and time of testing outcomes

^{Each black square represents a study and the bar within which it sits shows the statistical range of error (ie the range of results that may have occurred by chance). Squares sitting to the left of the vertical provide evidence that morning training may have been advantageous; squares to the right provide evidence that evening training may have been advantageous. A: when strength gains were assessed in the morning, morning training showed a slight tendency for better results. B: when strength gains were assessed in the evening, evening training showed a strong tendency for better results. C: when jump height gains were assessed in the morning, morning training showed a very strong tendency for better results. D: when jump height gains were assessed in the evening, evening training showed a strong tendency for better results.}

Practical recommendations for performance, health and fitness

The key finding here is that whichever metric of health or performance you look at, there doesn’t appear to be any real benefit to training at a particular time of day. So while performance tends to peak in late afternoon and early evening, the training and health adaptations you can expect are similar whether you train in the morning or evening. And because this study is was a rigorous synthesis of all the prior relevant research on this topic, we can be confident that its findings are pretty robust, despite some earlier research studies suggesting otherwise. 

In a way, these findings make life easier for athletes whose main goal is developing higher levels of strength, power and endurance or improving/maintaining health (eg losing body fat); if your daily routine precludes you from training in the evening, you can be confident that you are not losing out by training in the morning. Likewise, if you can’t train in the morning, then you can rest assured that your evening training is equally effective in helping you attain your goals. In plain English, choose your training time to fit in with your lifestyle and daily routine because you won’t be missing out!

However, another key (and very important) finding concerns athletes who are preparing for competition. In these circumstances, your regular training timing DOES matter – not whether it takes place in the morning or evening but whether it’s roughly aligned or not with the time of day you will be competing. For athletes who need to turn in the best performance in a particular event being held at a certain time of day, this study provides strong evidence (along with previous research) that you should routinely train at approximately the same time of day as your competitive event. At higher levels of sports performance, even small margins of time can account for the difference between victory and defeat. Therefore, a targeted alignment of your regular training time with the scheduled competition time can provide a major advantage.

“Your regular training timing DOES matter – not whether it takes place in the morning or evening but whether it’s roughly aligned or not with the time of day you will be competing.”

That said, this strategy is not universally applicable because competition times within a sporting discipline may vary during the season – eg soccer matches with morning or afternoon kick-offs. Even in sports were races or events tend to commence at roughly the same time of day (eg morning starts for marathons, triathlons and cycling sportive events), the strategy goes out of the window when travelling to events further away across different time zones. 

In addition, athletes such as track and field athletes and swimmers where qualification or knockout rounds typically take place earlier during the day and finals take place at a later time of day may have to be ready to compete at all times of the day. In these circumstances, the most logical approach might be to try and time your training sessions with more ‘time of day’ variability as your event approaches. That way, your body has the opportunity to better adapt to performing at a time or times of day outside of your regular training times!

^References

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