How could high frequency strength training lead to greater gains?

Recently, a study found that high- and low-frequency strength training were similarly effective for increasing muscle mass and strength in trained males, where the two programs involved the same weekly training volume (number of sets per muscle group).

To be fair, the low- and high-frequency groups improved their 1RM bench press by 5.6kg and 9.7kg, respectively, and their 1RM back squat by 8.0kg and 12.0kg, respectively. So the high-frequency group did achieve a non-significantly greater change in maximum strength for both exercises.

This greater increase in strength might be attributed to a larger practice effect, since doing an exercise five times a week might reasonably be supposed to cause greater improvements in coordination than doing the same exercise only once a week, even if the total number of reps is similar.

On the other hand, the low- and high-frequency groups achieved similar but very small increases in fat-free mass (0.6kg and 0.7kg, respectively). This is the result that needs thinking about, since the literature overall suggests that training a muscle 2 or 3 times per week leads to greater muscle growth than training it once per week, even when training volumes are (mostly) equated.

Before we can look at this finding, however, we first need to understand the relationship between weekly training volume and muscle growth.


How does weekly training volume affect muscle growth?

Assuming that you have everything else in your training program set up correctly (the right exercises for each muscle group, an appropriate proximity to failure, and basic things like sensible rest periods), then weekly training volume is the most important variable, when trying to increase muscle size as quickly as possible.

In fact, there seems to be a dose-response effect with weekly training volume, such that doing a greater number of sets per muscle group per week leads to greater gains in muscle size.

However, this dose-response effect is almost certainly subject to a threshold number of sets per week beyond which gains will not be increased further. At this point, muscle growth very likely stalls, and in some cases atrophy may even occur.


What can cause muscle growth to stall?

The research shows that muscle growth can stall whether we increase weekly training volume to excessive levels by either (1) increasing the number of workouts, or by (2) increasing the amount of volume we do in each workout.

Studies in rodents have shown that when we perform a strength training workout too soon after a previous, similar workout, this may not trigger muscle growth by increasing muscle protein synthesis rates, possibly because of elevated oxidative stress. Strength training often generates reactive oxygen species (ROS) as part of the process of muscle damage. The ROS create a pro-inflammatory environment, which causes oxidative stress.

Equally, doing a higher volume of training in a given workout leads to more muscle damage, and excessively-damaging, individual workouts with too much volume can cause muscle loss.

In both cases, the stalling probably happens because of too much muscle damage, whether accumulated over the week or in a single workout.


How does this study alter our understanding of training frequency?

This study indicates that training a muscle once per week has a similar effect on its size to training the same muscle 5 times per week. Assuming that the results can be taken at face value, there are at least two ways we could explain the findings:

  1. Training frequency has a smaller effect than we previously thought, and weekly volume is the overriding factor. So long as enough volume is done, it does not matter how many workouts the work is split out into.
  2. There is a U-shaped effect of training frequency on hypertrophy, and training once per week and 5 times per week fall on either side of the top of the curve, which lies around 2–3 times per week, as indicated by the previous research.

The research team working on this study went for option (1), which has the advantage of simplicity, but if we set the study in the context of the preceding literature, we might opt for (2).

Let me explain why.

In this study, the researchers also quantified muscle soreness in both groups, at varying points in the training program. This gives us a proxy for muscle damage sustained. The high-frequency group was almost never sore, because they trained with such a low individual workout volume for each muscle group. However, the low-frequency group was moderately or very sore throughout the program, indicating that they were probably still experiencing muscle damage even after several weeks of the same workouts.

This suggests that a high frequency group could perform a greater weekly training volume than a low frequency group, since muscle damage is the main factor that determines our ability to recover from a workout. And in either option, this would be expected to produce more muscle growth, so long as frequency was not so excessive that oxidative stress was still elevated at the point of the subsequent workout.

For me, this is the most important finding of the study, which is that training frequency almost certainly cannot be investigated in isolation of training volume (and other factors that influence muscle damage), since by increasing training frequency we reduce the volume in each workout, which reduces the muscle damage (and therefore the oxidative stress) caused by each workout.


What is the takeaway?

This new study indicates that training a muscle once per week has a similar effect on its size to training the same muscle 5 times per week. Whether this happens because the “sweet spot” for training frequency is 2–3 times per week or because weekly training volume is the overriding factor that determines muscle growth is unclear.

More importantly, this study demonstrates that training with a high frequency probably involves less muscle damage than training with a low frequency, when using the same weekly training volume. Since muscle damage is the limiting factor that sets how much volume we can do (either in terms of workout frequency or workout volume), this suggests that a higher frequency approach to training (up to a point) may allow lifters to do more weekly volume, and therefore achieve greater gains in muscle size.