When I think of the relationship between volume and intensity for hypertrophy, I like to use a cooking analogy: Training intensity is the heat on the stove. Training volume is the total amount of cook time.
If you want to boil water on the stove you wouldn't put the flame on the lowest setting - the water would never reach a rolling boil no matter how much time you gave it. Instead, you would set the flame to the appropriate intensity and then lend it the appropriate time it needs to work its magic and make the water boil.
Assuming all of the volume is done in a sufficient intensity range, volume is going to be the primary driver of hypertrophy. That's all well and good, but I'd like to clear the waters a bit and unpack that statement and why I believe it to be true.
When we discuss training volume what we're really talking about is total work done in a session, across a week, or in a cycle. Different coaches have different ways of calculating training volume, and the reality is it doesn't matter all that much as long as you use the same method consistently for internal validity. However, when dealing with strength & hypertrophy work there are three primary ways people tend to skin the cat.
1. Tonnage tracking where volume = reps x sets x weight lifted (ie - 5 reps x5 sets @200lb = 5,000lb of volume)
2. Rep tracking where volume = reps x sets (ie - 10 reps x 8 sets = 80 reps of volume)
3. Set tracking where volume = the number of sets completed
As it relates to hypertrophy training specifically, I believe the third option is the most valid measurement to track over time as it most closely correlates with muscle growth whereas #1/2 can go up within training without imposing a greater growth stimulus. For example, if you do 5x5 Back Squats @200lbs you set 5,000lbs of volume and if 6 weeks later you do 5x5 @250lbs you get 6,250lbs of volume. Despite the fact that this is a ~20% increase in total work the degree of mechanical tension of the muscle is similar (since the athlete is stronger), which means the hypertrophy stimulus is no greater.
This may create some controversy, especially if you take the story of milo and the bull to be true and have continually been told that progressive overload is the driver of hypertrophy. Based on the current body of evidence, it appears that adding load to the bar does not cause you to grow directly. If you can lift a heavier load it’s because it’s already within your current capabilities. You did not grow because you lifted a heavier weight. You can lift a heavier weight because you grew. The causality is reversed
Why add load to the bar at all then? Well, if your hypertrophy training is doing what it should be doing, then you need to add load to the bar because your muscles are larger. Technically you don’t have to add more load and you can just keep pushing rep volume higher for a period, but at some point this will become impractical, your strength will increase enough that the load is no longer heavy enough to stimulate further growth, or your intra set reps will get so high that you cannot accumulate significant set volume due to fatigue damage.
Traditionally those who want to hypertrophy a muscle train with frequencies ranging from 1-2 times per week per muscle group. An example of this could be the traditional ‘bro split’ where each muscle is hit once per week or an upper/lower, or push/pull/legs, split where each muscle is hit twice. In untrained individuals, or for those on gear, these frequencies are probably a pretty good place to be. But, for most intermediate to advanced athletes, they are more than likely sub-optimal if muscle growth is the primary training goal and they are able to effectively recover from their total training load. Additionally, training frequency for a given muscle becomes increasingly more important as the volume gets higher.
There’s a limit to the amount of 'effective sets' you can do in a session, and based on the current body of evidence it appears that limit ranges from ~8-13 sets for a given muscle group. A reason for this is that the accumulation of neuromuscular fatigue and muscle damage can reduce performance, muscle activation, and mechanical tension more and more with each additional set performed.
This ties into the concept of repeated bouts, which says that the magnitude of 'adaptation' you get from each subsequent set gets smaller and smaller, so past a point, additional work sets provide little to no benefit. Then as you push past that point, each additional set may not only not provide additional benefit, but may reduce adaptation. Additionally, continuing to train after this point may result in negative protein balance as you further increase muscle protein breakdown levels without stimulating more muscle growth.
A maximum productive training volume per workout would also explain why some but not other studies find benefits of higher training frequencies. One of the prominent studies in support of high-frequency training was the Norwegian frequency project, conducted by Borge Farelli and done on elite powerlifters. In this study, they saw greater strength and hypertrophy with 6 sessions per week versus 3, where volume was equated between the two groups. This was likely due to the fact that spreading the work across more sessions allowed for higher quality. On the flip side, many of the lower volume studies show no additional muscle gain with higher frequency, which would make sense as it's not warranted in those scenarios. However, no studies to the best of my knowledge have shown a detriment of higher frequency when the volume is equated.
So, this leaves us with the concept that frequency is a function of overall training volume, and as a result, the total weekly volume dictates how many times we should optimally train a muscle. There is some nuance and individual variability here, but some practical recommendations would be...
5-10 sets per week = 1 session
10-15 sets = 2-3 sessions
15-20 sets = 2-3 sessions
21-25 sets = 3-4 sessions
25-35 sets = 4-7 sessions
Before jumping to some of these higher volumes and frequencies keep in mind that there's a difference between what you can handle in terms of training volume and what gives you benefit. For example, I can train my back every day of the week without any major issues coming up and while still making some training gains. But, is that optimal and could I make better gains with a lower frequency? Based on my experience, the answer is yes. For me, it seems the sweet spot is ~24-28 sets per week over 3-4 training sessions during specialization cycles and closer to ~18-22 sets per week when chronic load is higher. For others, the sweet spot may be wildly different. It's important to figure these things out for yourself through experimentation over time, and to start lower than whatever you think you need - there's no rush to train with high volume and you may, in fact, be doing yourself a disservice.
Written by Evan Peikon