Best Time to of day to weight train and the science behind it

If the aim of your workout is to increase your muscle size, allowing you to become bigger and stronger, then it may be important to pay attention to WHEN you are working out, as well as how.

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    So what time of the day should you work out? Well, there is no one correct answer to this question as your workout time should be dependent on a variety of factors. There are pros and cons of each workout depending on what time you choose to train, however, scientific studies have shown that, in general, an afternoon workout is better suited for muscle growth. Keep reading to find out why.

    The Science Behind the Facts

    There have been many studies focused on what time of the day is the most effective for workouts. Some of the best data has been collected during a Finnish study conducted in 2009 at the University of Jyväskylä.

    The study focused on men, split into two separate groups who trained either in the morning or in the evening over a period of 10 weeks. Both groups trained for two hours every day call by either from 7:00 am to 9 am, or 5 pm to 7 pm. The only thing that was different was the time of their training as the length and training programme was identical. The programme included cardio and weight training.  After a period of time, the scientists then measured the thigh muscle using an MRI scan. The muscle was measured at week 10 and after 20 weeks, while the strength of the muscle was also measured at these points. The muscle was measured at the same time of day between 9 am and 4 pm.

    The results of the study found that while every individual that took part in the experiment increased their muscle strength and size, the average muscle gain for the afternoon session athletes was 3.5%. In comparison, the morning results were only 2.7%. The increase in the size of their thigh muscles as measured by the MRI found that the thigh muscles of the afternoon workout group were 30% larger than those of the morning group. Unfortunately, the difference in these results was not enough to be statistically significant.

    To try and solidify these results, a follow up study was commissioned that worked over the span of six months; however, the results were the same, although strength and muscle growth were larger due to the increased period of time. The outer thigh size increased by 12% in the morning half of the group, while the evening group saw their size rise by around 50%. This led to scientific evidence that muscle mass was more likely to develop when workouts were performed in the evening compared to in the morning as both groups were completing the same workout routine.

    Why Are Evening Work Outs More Effective?

    For most people, their muscle strength reduces in the morning when they wake up and increases throughout the day, reaching its peak in the evening. This is not just in those who already work out but can instead be found in the general population. One clinical trial found that muscle performance was at its highest in the evening but only for specific exercises – particularly ones that involved lifting weights at a faster pace. The study was conducted on a group of men in their early twenties. The men performed multiple strength tests at various points throughout the day – 8 am, 12 pm, 4 pm and 8 pm using an instrument known as an isokinetic dynamometer which measures not only strength but the speed of movements.

    As well as finding that there was an improvement in the fast movements in the evening for younger men, the results were also similar in older men. While the peaks in strength and energy happened at the same time, there was not as stark a difference in the older men compared to the younger age group.

    The reason behind the more remarkable performance in faster movements than slower movements is linked to the fibers of the muscle. When the force requirements of the machine were high, the muscle fibers are activated and are more effective at a higher body temperature. A higher body temperature is more likely to happen in the evening than the morning, and therefore, the muscles are more likely to be effectively engaged at the end of the day. Due to this, weight lifting and other strength-based exercises are often more likely to make an impact on your body and muscle growth in the afternoon and evening.

    Cardiovascular exercise can also benefit from evening exercise – one study found that power output during study subjects cycling sprints was higher when the sprints were undertaken in the afternoon rather than the evening. Additionally, body muscles were found to be more powerful (by around 8%) during evening cycles compared to morning ones when subjects were tested roughly 12 hours apart.

    The Impact of Chronotypes on your Workout

    Your chronotype is your own personal body clock that dictates your day. It impacts the circadian system and leads to peaks in your behaviour, cognition and physiology throughout the day. Every individual’s circadian system works differently, and this has to be taken into consideration when working out when the best time to exercise is.

    To put it simply, most people are either morning people or evening people, and this can impact when we are most alert and active. Studies on the American population found that around one in four people function better in the morning, while another one in four are better at night. The other half of the population were described as ‘neither types’ and did not show a preference. If you are unsure what your chronotype may be, consider your lifestyle. Morning types wake up early, are most productive in the morning, go to bed early and sleep very well. On the other hand, night types find it more challenging to get to sleep and generally go to bed later. They feel most active and productive in the evenings or afternoons and sleep later in the morning.

    Why is this related to your workout?

    Well, to put it simply, morning types are more likely to benefit from a workout when they wake up rather than waiting until the end of the day. In general, they will feel less tired, feel like the workout is easier and will have better performance in the morning, especially in comparison to evening types or those who do not have a chronotype at all. This is backed up by an Italian study that found that those who described themselves as morning types were more likely to find interval training harder in the morning than if they did the same level of exercise in the evening. Conversely, evening types found the interval training much more difficult in the morning than in the evening, even though the activity for both groups was identical.

    When it comes to waking up and starting their day, evening types need longer to fully wake up and do not reach their optimal performance levels as quickly as morning types – with the strength of growth signals sent to muscles also being different depending on the time of the workout. Studies have shown that growth signals sent to the muscles have been found to be more consistent when weights are lifted later in the day. Higher peaks, however, can be found in the morning in some people (morning types), but evening types may experience a growth signal drop during this time. 

    Researchers stated that “We found that early morning may induce significantly higher between-subject variation in some muscle growth- or metabolism-related signalling pathways compared to the same loading later in the day.” This means that training in the morning can lead to peak muscle building for morning types who feel energised at this time, but not for evening types who find exercise at this time more difficult.

    What If You Can Only Work Out in the Morning?

    If you can only fit your workout into your busy schedule in the mornings, it is still possible to see some good results. Your body is easily adaptable and can get used to training at different times of the day. While your body may feel slightly weaker in the morning initially, it can begin to adapt to your routine, allowing it to become easier and reducing the difference in performance. One scientific study discovered that both morning and evening athletes had the same levels of peak torque and peak anaerobic power after a period of training.

    Another aspect to consider if you are working out in the morning is caffeine. Studies have shown that caffeine which is taken before a workout, can help raise your performance as it combats the so called ‘morning decline’, which limits your strength and power.

    Other Factors to Consider When Deciding on Your Work Out Time

    While we have discovered that the best time to work out is the afternoon or early evening, this is a generalisation that does not work for everyone. The reason for this is that the idea behind working out in the afternoon is that your muscles are at their peak during this period. If, however, you have a job that is physically demanding, this may be counter-productive as your muscles may already be exhausted and fatigued after your work. Consider switching to a morning workout to get the most out of your body in situations like this.

    Mental fatigue is also important to consider, although it is often forgotten. Working out requires focus and concentration, so if your job leaves you mentally exhausted, consider changing to a morning routine. A research project from the Frontiers in Physiology Journal found that “Mental fatigue has been shown to reduce time to exhaustion during high-intensity cycling, reduce average running speed during a 5-km running time trial and increase the perception of effort during a prolonged submaximal isometric contraction.” So, it is essential to make sure that you are mentally and physically well enough to work out at the end of the day.

    There are other aspects to take into consideration – if you work out at a public gym, they are often quieter in the mornings, meaning that you are more likely to have access to the equipment that you need. Exercise also produces endorphins that boost your mood and lead to higher levels of energy throughout the day – meaning that many want this feeling in the morning instead of the evening. The most important thing is that if you are working out in the morning that you do this consistently in order for your body to adjust and adapt to your routine.

    Wrapping Up

    While technically working out in the afternoon or early evening does have some benefits, as identified in scientific studies, such as increased muscle growth. However, the results are not so dramatic that you should not even consider working out at different times of the day.

    About The Author

    Michael Collins

    Michael Collins

    Michael is a gym enthusiast with experience that spans more than 20 years. He started his exhilarating journey of keeping fit in his late teens, and over the years, he has immensely grown to become a resourceful gem in matters of fitness.

    He has been writing for many years, focusing on answering all the questions you may have on nutrition, muscle building and fitness. Keeping fit and staying healthy is his main passion, and this is evidenced in the articles he writes in a simple and understandable language out of intensive reading and real-life experiences.