In part one of this series, we covered the research looking at diurnal variations in physical performance. In specific regard to strength and power, the research indicates we naturally have the highest potential to produce force in the late afternoon/early evening. Also, we learned that muscle hypertrophy adaptations may be superior when training later in the day.
In this segment, we’ll be evaluating other important factors to consider when selecting a time-of-day to exercise. This includes body temperature, chronotype, and consistently training at the same time-of-day. Further, we’ll establish whether or not these variables can offset the observed diurnal variations in anaerobic performance.
Impact of Warm-up
A major factor explaining diurnal fluctuations in anaerobic performance is body temperature. Indeed, body temperature rises over the course of the day and reaches its peak at approximately 6 p.m. While this is a natural phenomenon, we can also increase our body temperature through artificial means, such as through modulating our environment and/or our warm-up strategy.
This then leads to the question, if we can increase our body temperature to a point that matches its circadian peak, will this counterbalance the observed attenuations of strength and power while training in the morning?
In this study, the researchers examined the impact of warm-up duration and time-of-day on performance in a loaded counter-movement jump. Subjects completed four different sessions in random order. Two tests were performed at 8 a.m. and two tests were performed at 4 p.m. At each time point, subjects performed either a controlled warm-up or an extended warm-up.
Both warm-ups featured a pretty standard medley of dynamic movements. The primary difference between the interventions was that the extended warm-up also included cycling on a stationary ergometer for 20 minutes.
The results of this experiment displayed substantial differences in performance between the a.m. and p.m. control groups (which is what we would expect). Following the control warm-up, peak power, mean power, and jump height were 4-6% higher in the p.m. group.
In regards to the extended warm-up conditions, it was found that body temperature following the extended warm-up in the a.m. matched the post-warm-up value in the p.m. condition utilizing the control warm-up. Consequently, this led to no substantial differences in performance between these groups. This indicates that when you increase body temperature equivalent to a normal whole-body temperature experienced in the late afternoon/early evening, this can blunt time-of-day differences in force output.
Similarly, in a trial that utilized a Wingate test for the intervention, it was found that extending the warm-up duration from 5-minutes to 15-minutes significantly improved peak and mean power when testing was performed at 8 a.m. In contrast, extending the warm-up duration had no effect on performance when the test was completed at 6 p.m. These results further suggest that when training in the morning, extra time should be allocated to the warm-up period in order to maximize subsequent exercise performance.
Transitioning to something you might have a little less control over, but even so, is worthy of consideration, is the temperature of the environment you are training in.
In this interesting study, subjects performed two different jump tests (a squat jump and a counter-movement jump) and a brief maximal sprint on a cycle ergometer in four different conditions. The tests were performed in the morning (between 7 a.m. and 9 a.m.) in a neutral environment (laboratory temperature of 20℃ and 70% humidity), in the morning in a warm environment (29℃ and 57% humidity), in the evening (between 5 p.m. and 7 p.m.) in a neutral environment, and in the evening in a warm environment.
The results showed that the power developed in the neutral environment during the countermovement jump was significantly higher in the afternoon than in the morning (which is in concert with the rest of the data on the topic). This was also the case for the cycle ergometer sprint.
For the warm environment, there were significant improvements observed in both countermovement jump and squat jump power in the morning. This led to comparable performance between the morning and evening conditions. Following suit, similar performance was observed on the cycle ergometer sprint test between the morning and evening conditions when performed in a warm environment.
Jointly, these data demonstrate that when body temperature is increased to levels observed at the acrophase of the rhythm through artificial means, typical poor morning training performance can equate to evening levels.
Moving on from these compelling findings, let’s explore some other factors which could impact performance at different times of the day. One variable to consider is your chronotype. Put very simply, when do you like to train? When do you feel you perform the best?
Impact of Chronotype
A person’s natural inclination with regard to the times of day when they prefer to sleep or are most energetic is known as their chronotype. Chronotypes have been mainly assessed by questionnaires designed to associate an individual’s tendency towards “morningness” or “eveningness.”
The questions used on these tests are mostly subjective, relating to when you feel best for various tasks or to the habits of others (i.e. “I wake up later than most people”). Based on your score, you will be identified as a morning type, an evening type, or a neither/intermediate type. Depending on the test, there may also be sub-categories such as extreme morning type, moderate morning type, moderate evening type, and extreme evening type.
Most people intuitively have an idea of their chronotype and are conscious of the fact that they are more alert and energetic at certain times of the day. These feelings may primarily dictate when an individual performs an activity, but can an individual’s proclivity for when they like to exercise really override physiological fluctuations in performance? Or could relying on subjective markers lead to training at a sub-optimal time-of-day?
In this study, they measured differences in maximum voluntary contraction (measured via the 6-second isometric grip strength test using an electronic hand dynamometer) at three separate times of day (2 p.m., 8 p.m., and 8 a.m.). The chronotype of each subject was assessed using corrected mid-sleep on free days from the Munich Chronotype Questionnaire.
The results of the experiment displayed a significant interaction between time-of-day and chronotype. Early chronotypes performed significantly better in the afternoon compared to the morning and evening. Late chronotypes performed significantly worse in the morning compared to both the afternoon and evening, with their best performance taking place in the evening. Further, at 8 a.m., early chronotypes performed 7.4% better than late chronotypes, whereas, at 8 p.m., late chronotypes performed 3.7% better than early chronotypes.
In another study on competitive field hockey players, subjects completed the BLEEP test (a progressive aerobic cardiovascular endurance test used to estimate an athlete’s maximum oxygen uptake) at six different time points (7 a.m., 10 a.m., 1 p.m., 4 p.m., 7 p.m., and 10 p.m.). The chronotype of each participant was assessed by the RB-UB chronometric test.
It was found that the best performance for early chronotypes occurred around 12.19 ± 1.43 (early afternoon) hour, intermediate chronotypes at 15.81 ± 0.51 hour (mid-day), and late chronotypes at 19.66 ± 0.67 hour (evening).
In addition to chronotype, both of these studies found an interaction between time since entrained awakening and performance.
In study one, it was found peak maximal voluntary contraction performance occurred around 6.7 hours after entrained awakening for early chronotypes and around 12.6 hours after entrained awakening in late chronotypes. In study two, peak performance occurred approximately 5.60 ± 1.44 hours after entrained awakening in the early chronotype and 11.18 ± 0.93 hours after entrained wake-up in the evening types.
While these findings don’t necessarily change the fact that early chronotypes tend to perform better earlier in the day and late chronotypes tend to perform better later in the day, this additional variable of “how long has the athlete been awake?” is another important consideration when selecting a time-of-day to train.
Outside of research evaluating objective markers of performance, it has been shown that an individual’s chronotype impacts their level of motivation heading into a training session and the perceived difficulty of it.
Morning types tend to report a higher rating of perceived exertion for activity performed in the evening and evening types tend to report a higher rating of perceived exertion for sessions performed in the morning. The same applies to levels of motivation. These subjective factors are vitally important because they can impact voluntary training intensity and total work completed within a training session.
Overall, it appears an individual’s proclivity for morningness or eveningness is an important factor to consider when it comes to selecting a time to exercise. While there are a variety of questionnaires to assess an individual’s chronotype, it is still ultimately a subjective marker which brings some uncertainty. An individual may very well not possess a firm grasp of their genetic predisposition and when they are truly at their best. As such, it’s likely worthwhile to experiment with training at a few different times of the day and collecting some sort of objective marker of performance in order to determine what time resulted in the best training sessions.
As we’ve established, we can reduce time-of-day variations in physical performance through increasing body temperature. We can also ensure peak performance by simply training at the time-of-day when an individual perceives to be at their best, but what if someone has to train at a time that conflicts with their biological clock?
Let’s create a hypothetical scenario with an individual named John. John works a typical 9-5 job. He is also a father of two children. In his free time, he enjoys lifting weights and has a particular interest in maximizing strength and muscle hypertrophy adaptations. Everyday, John comes home from work and takes his two sons to basketball practice. He picks up his kids from practice at 6:30 p.m. and is then responsible for cooking dinner for everyone when they return home.
John is aware of the scientific literature demonstrating that performance for anaerobic activity tends to be superior later in the day. He is also pretty certain that he possesses an evening chronotype. Despite this, he trains at 6:00 a.m. before work because this fits best with his schedule. Should he be concerned about potentially leaving gains on the table through not optimizing the time-of-day in which he trains?
Impact of Training at a Consistent Time-Of-Day
You may be in a very similar situation to the above example. You’re interested in checking every box in order to maximize muscle and strength adaptations but are ultimately restricted by your lifestyle. Since you’re not fortunate enough to lift weights full-time for a living, you are forced to train at a time-of-day which on paper appears to be sub-optimal for performance, but is this set in stone?
Sure, maybe training in the morning tends to result in inferior strength and power, and your chronotype is more suited towards the evening, but if you consistently train in the morning will you eventually adapt and be able to express your maximum potential at this time? Or will your full potential never be realized? Let’s see what the research has to say.
In this study, the researchers aimed to determine whether there is an effect of time-of-day on the adaptation to strength training at maximal effort. Before the intervention, each subject’s peak anaerobic power (measured through the Wingate test) and peak knee extension torque (measured on an isokinetic dynamometer) were recorded in the morning (between 7 a.m. and 8 a.m.) and in the evening (between 5 p.m. and 6 p.m.).
Following the initial tests, peak torque and peak anaerobic power were significantly higher in the evening than in the morning testing session (surprise, surprise).
Subjects were then randomized to perform all of their training in the morning or evening for 6-weeks and then tested again. Participants trained twice per week with a focus on the quadriceps using a leg extension device. A lighter load was used for the first 3-weeks of training (60, 70, and 80% 1RM) and a heavier load (90, 93, and 95% 1RM) was utilized for the last 3-weeks.
At the end of 6-weeks, it was found that the morning training group improved their peak anaerobic power in the morning and in the evening tests. Similar results were found for peak torque. Meanwhile, the evening training group improved their peak anaerobic power and torque in the evening, but not in the morning.
Over the duration of the study, the morning group experienced larger absolute increases in training performance compared to the evening group, which can largely be explained by baseline performance being much worse in the morning, leaving more room for improvement. This led to similar peak anaerobic power and knee extension torque between groups at the end of the trial.
The results of this trial showed that training at a specific hour increases peak torque and peak anaerobic power specifically at this hour. This indicates that despite being primed for superior anaerobic performance in the late afternoon/early evening, you can mitigate poor morning training performance by consistently training in the morning.
In another study examining the effects of training at the same time-of-day on diurnal variations in anaerobic performance, subjects performed a maximal brief squat jump, countermovement jump, Wingate test, and 1RM test on leg extension, leg curl, and squat in both the morning (between 7 a.m. and 8 a.m.) and the evening (between 5 p.m. and 6 p.m.) before an 8-week strength training intervention.
Subjects were then randomly assigned to perform all training in either the morning (between 7 a.m. and 8 a.m.) or the evening (between 5 p.m. and 6 p.m.) and then re-tested at the end of the intervention. Training consisted of 3 sessions per week and focused on the lower body musculature using the leg extension, leg curl, and squat. Traditional hypertrophy-style training was performed for the first 2-weeks and strength-oriented training was performed for the last 6-weeks.
Prior to the 8-week intervention, the results displayed that the average 1RM strength for all three exercises was superior in the evening.
Following the 8-week intervention, the observed reduction in strength during the morning disappeared in the morning training group. Similar results were also found for performance in the Wingate test, squat jump, and countermovement jump tests.
Based on the available research, it appears that strength training performed in the morning hours can improve typically poor morning performances to the same level as the normal daily peaks observed in the evening. As such, if you’re a bonafide night owl who has to train in the morning, don’t worry. While your baseline strength and performance might be lower at this time, initially, you will quickly adapt and eventually be able to express a level of strength and power on par with what you’re capable of in the evening.
Summary and Practical Takeaway
Despite natural fluctuations in performance over the course of the day, we can suppress these oscillations through a variety of means. For starters, we can simply train according to our chronotype, or the time-of-day we perceive to have the best strength and energy. While average performance tends to peak in the late afternoon/early evening, you may very well be a morning lark or possess a proclivity for extreme morningness and innately perform at near peak capacity in the early hours of the day.
Further, even if you’re not genetically primed for decent morning training performance, you can mitigate this by utilizing an extended warm-up in order to raise total body temperature to a level comparable with its circadian peak later in the day. You can also modify the temperature in the environment as a way to artificially raise body temperature. If you don’t have control over the thermostat of your training space, try throwing on an extra layer of clothing.
Lastly, simply training at the same time-of-day consistently will facilitate improved training performance at this time. That means the observed morning slump will cease to exist after a period of acclimating to morning training. As such, it is recommended that strength and power athletes required to compete at a certain time-of-day to coincide training hours with the time-of-day at which one’s critical performance is planned.
So, does the time-of-day you train at really matter? Probably not. The research on muscle hypertrophy adaptations is quite fascinating, but there simply needs to be more research conducted in this area before we can be sure that it’s worth reorganizing our schedule to train at night.
Besides, we know improvements in strength performance over time in a moderate rep range is a great proxy for muscle hypertrophy, and as we discussed, through several strategies, we can express similar performance in the morning as the evening, despite our primal inclination to be at our strongest and most powerful later in the day.