For the average person the main constraint they have when it comes to exercise is time. There are only so many hours in a week, and when you are someone who has a full time job, family responsibilities, and recreational activities you enjoy doing, most people can only allocate a few hours a week at most to actual exercise.
With precious little time to exercise, lots of people wonder what is the best way to split up that time to reach their goals.
For example…
Is it better to lift 5 times a week for 20 minutes or 2 times a week for 45 minutes?
Should you run 3 miles 3 times a week or do one run of 9 miles?
Before we look at the tradeoffs between different frequencies of exercise throughout the week it would first be useful to get some insight into how much exercise one needs to do for health, wellness, and longevity.
In terms of aerobic exercise, there is an interesting meta-analysis [1] done on runners that shows how much time someone needs to run a week in order to reduce various causes of death. This diagram lays out the findings perfectly
https://www.mayoclinicproceedings.org/article/S0025-6196(15)00621-7/fulltext
If you look at all cause mortality, meaning dying of any cause whatsoever, we see a drastic reduction from not running to doing less than sixty minutes a week. Doing more than 60 minutes a week nets you a little more of a reduction but beyond 95 minutes a week up until 151 minutes a week you see a trivial reduction. After you start to cross the 151 minutes a week mark, your risk can start to increase (more on this later in the post).
What about resistance training, how much do you need to do for optimal health, wellness, and longevity?
The results of a recent study might surprise you.
The figures above come from a recent 2022 study. All cause mortality seemed to be lowest at around 40 minutes per week….40 minutes! Cardiovascular disease, cancer, and diabetes also showed that somewhere between that 40-50 minute mark appeared to be optimal [2].
So whether it’s aerobic exercise or resistance training you don’t need to do a whole lot…but you should be doing both!
Let’s make this more concrete with a real life example.
Say you are really strapped for time and you have 2 days a week you can exercise for about an hour on each of those days. The frequency of exercise would be 2 days and the total duration you have is 2 hours.
When discussing the topic of exercise frequency it’s important to understand the concept of volume. Volume refers to the total amount of work you are doing across a week. To figure out the amount of volume of resistance training you are doing you multiply sets x reps x load. Load is the amount of weight you are using. Reps refers to the number of repetitions you do of the weight for a given exercise. Sets are the number of times you repeat that exercise at that set using the given weight. In addition we can break down volume and look at volume for each muscle group, legs, back, chest, and arms.
When discussing volume in terms of cardio exercise you look at the total minutes you do per week and at which intensity (heart rate). Intensity is important because you can do a large amount of easy aerobic exercise, but to try to replicate that amount of cardio exercise at a much higher intensity will be nearly impossible.
With the concept of volume under our belts, let’s now head back to the research to see if you can actually be healthy and look good with just 2 days and 2 hours of exercise.
In a study[3] done on 38 overweight women, researchers split the women into 2 groups and had both groups do 150 minutes a week of exercise on an exercise bike. The difference between the groups was that one group did 30 minutes of exercise 5 times per week, the other group exercised for 75 minutes twice a week. Both groups performed the exercise intervention for 8 consecutive weeks at the same intensity. At the end of the 8 weeks, there was no difference in glucose, insulin, HOMA-IR, cholesterol, triglycerides, or inflammation between the two groups.
Now based on the all cause mortality data for aerobic exercise above we know that 150 minutes is more than enough in terms of volume and I suspect 60 minutes would yield the same results. The important finding from this study is that splitting up the training into 2 days across the week was no different than splitting up across 5 days WHEN DOING BOTH AT THE SAME INTENSITY.
What about if your goal is to improve strength and/or body composition?
There are A LOT of studies that have looked at frequency and duration in terms of resistance training, for this reason it can be useful to look at meta-analysis, a study of many studies, to get a sense as to what the general consensus is across these studies.
In a meta-analysis looking at strength gains between one, two, and three plus days a week of training, there were no significant differences in strength between training one day a week, two days a week or more than three days a week as long as training volume was the same [4].
In a meta-analysis looking at hypertrophy, i.e. increased muscle mass, here is a summary of the author’s findings
https://twitter.com/BradSchoenfeld/status/1109135599666114560?s=20&t=YsIEaPhUExuHGUtWh0VdZw
The summary here is that for hypertrophy training two times a week may have a slight advantage to once per week as long as the volume is the same. This makes sense in terms of hypertrophy because the act of resistance training turns on what is called muscle protein synthesis (MPS) which is a key factor in triggering muscle growth. This MPS signal declines once the training session finishes, so doing something to trigger it again at another point in the week is going to be beneficial.
https://www.frontiersin.org/articles/10.3389/fnut.2019.00146/full
For our fictional situation above where someone only has 2 days a week to train for an hour at a time what do we do? What I would suggest to someone in this situation I would do the following…
On day 1 you do 40 minutes of easy cardio (zone 2). For the remaining 20 minutes I would do some resistance training consisting of one big compound movement like a deadlift, squat, bench press or overhead press. Alternatively you could superset a couple of isolation exercises like bicep curls and triceps or lat pulldowns and cable rows together and do a few sets of those.
On day 2 you would do 40 minutes of resistance consisting of 2 compound exercises (that you didn’t do on day 1) and then a few additional complementary or isolation exercises. For the remaining 20 minutes I would do a high intensity interval session to work the high end of your cardiovascular system.
Here are some relevant blog posts on zone 2 cardio, high intensity interval training, and resistance training that you can use to actually make these two days more concrete complete with durations and specific exercises you can do.
At this point you might be wondering why anyone would want to work out more if they don’t have to?
For some of us, myself included, working out is something they enjoy. Going to the gym, going out on a run, riding their bike…these can be more than just a means to be healthy, it’s an activity that has become part of their life.
In addition, while 2 days a week of exercise is enough to keep you healthy and looking good, it’s unlikely to be detrimental if you exercise 4 or 5 days.
Obviously there is an upper limit to the amount of exercise you can do, as you can see in the figures above regarding the amount of resistance training and cardio you need to do to not die of cancer, cardiovascular disease, diabetes, and all causes there is not a linear decrease in risk the more you do. In fact when you get to the pointy end of those graphs your risk starts to go up! So yeah, when taken to the extreme adding more exercise won’t do you much good.
If you do add a 3rd, 4th, or 5th day of exercise you can see additional benefits in muscle development and cardio fitness. You could even add more time to your 2 days a week to add in additional volume and get additional benefits if you had the extra time. The limit you eventually run into is your ability to recover.
If you add in more volume with additional time or days of exercise, but cannot recover from it, it’s actually going to be worse for you. For example, researchers had 26 men do 8 sets of 10 reps of the bench press to failure. The study showed that it took 72 hours for the participants strength to return and 96 hours for their ability to repeat that volume again [5].
If it takes 3-4 days for you to recover from an exercise session there is a pretty good chance you wouldn’t be able to get in your 2 days of training per week that you need to get in just for health and wellness.
And it’s not just your physical capacity that can be affected by too much training volume, your sleep can be negatively affected, your appetite might increase or decrease, your mood might deteriorate, your mental capacity could be negatively affected. Again, we can see how too much training can start to affect your overall health.
If you can/want to do more than 2 days of exercise a week, I encourage you to do so, but you need to scale up slowly. If you can exercise four days a week for an hour, do not max that out to start! Instead, what I would do is exercise for 35 minutes for 4 days. That comes out to be 140 minutes a week, 20 minutes more than if you were able to workout 2 days a week for an hour. In this model you have not only more volume and potentially increased your strength, hypertrophy, and aerobic fitness but you have plenty of room to continue to progress from here. In addition because you are making small increments in volume you decrease the risk of not being able to recover.
Let’s return to the questions we started with…
Is it better to lift 5 times a week for 20 minutes or 2 times a week for 45 minutes?
Should you run 3 miles 3 times a week or do one run of 9 miles?
Either protocol will work, both should yield the same results as long as the same volume is performed. You can get more results by adding more volume, but you need to be able to recover from that additional volume or you will actually see negative results. At a minimum you should shoot for exercising 2 days a week with a mixture of cardio and strength training. If you can add more volume via more time or additional days do so SLOWLY and track subjective markers of recovery along the way.
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- (2015, September 8). Effects of Running on Chronic Diseases and Cardiovascular and All …. Retrieved January 13, 2023, from https://www.mayoclinicproceedings.org/article/S0025-6196(15)00621-7/fulltext ↑
- (2022, February 28). Muscle-strengthening activities are associated with lower risk and …. Retrieved January 10, 2023, from https://pubmed.ncbi.nlm.nih.gov/35228201/ ↑
- (n.d.). Effect of Exercise Programs With Aerobic Exercise Sessions of …. Retrieved January 10, 2023, from https://journals.humankinetics.com/view/journals/jpah/12/1/article-p80.xml ↑
- (2018, August 3). Weekly Training Frequency Effects on Strength Gain: A Meta-Analysis. Retrieved January 11, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6081873/ ↑
- (2017, October 1). Dissociated time course between peak torque and total work …. Retrieved January 12, 2023, from https://pubmed.ncbi.nlm.nih.gov/28595855/ ↑