The Optimal Training Frequency for Muscle Growth

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Reading time: ~6-7 minutes

This is part 2 of the Training Frequency series. Part 1 was on strength – click here to read it!

Takeaways for the effects of frequency on hypertrophy gains:

  • A higher frequency (4+ x /week) is probably better for hypertrophy than a lower frequency (1-3x/week), though the paucity of research and methodological differences make a firm conclusion hard to draw.]
  • A frequency of 2-4 times a week likely outperforms a frequency of 1-2 times a week.
  • If you want to try high frequency training, keep weekly volume the same at first. After a month or so, if you respond well, and don’t feel like you’re overdoing volume, try increasing it slowly and see how you respond. If you feel under-recovered and/or your performance is decreasing with the same weekly volume as when you were training with lower frequency (and you aren’t more stressed, eating less and/or sleeping less than before) then high frequency training might not be for you.
  • There might be a benefit to training more often than less often on a volume-equated basis, all the way up to 6+ times a week.
  • Arguably, one of the main reasons to use a higher frequency is because they are permissive of higher volumes for most people.

Low vs High Frequency for Hypertrophy

What prompted me to write this series of articles were the recent meta-analyses done by Grgic et al. (2018), Greg Nuckols (2018) and Schoenfeld et al (2016).

A lot of people, particularly if they’ve been immersed in bodybuilding culture for a while, would presume that  bodypart splits (low frequency training) reign supreme for hypertrophy. When you take a look at the research, however, things become a little murkier.

Up until 2018, there hadn’t actually been that much research on training frequency and its effects on hypertrophy and strength gain. During this past year, however, quite a few studies investigating that topic have been published.

So, what’s the optimal frequency for increasing muscle mass? How large is the difference between frequencies? How do you determine your own optimal frequency? These are the questions this article looks to answer.

Without further ado, let’s get right into the results of these meta-analyses.

Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis by Schoenfeld et al. (2016)

Key takeaways:

  • 2x/week frequency outperformed 1x/week. All studies favoured higher frequency. Some studies weren’t volume-matched but were included for analysis. Most high frequency groups used a frequency of 2-3x/week, while most low frequency groups used a frequency of 1x/week.

  • Due to lack of studies/sample sizes, it couldn’t be determined whether or not 3x/week outperforms 2x/week.
  • According to this meta-analysis, if you want more hypertrophy, you’re probably better off spreading your weekly volume for a muscle group over 2 or more sessions than a single one.

Results:

This meta-analysis found that higher frequency groups saw larger increases in hypertrophy than their lower frequency counterparts. Most of these studies had frequencies of 1-3x/week.

The authors were unable to determine whether training a muscle group 3 times a week outperforms 2 times a week. This is primarily due to small sample sizes and a lack of research at the time (this review was published in 2016).

Discussion:

What does this mean for your own training? Well, going off this meta-analysis alone, it’s probably almost always better to train every muscle group 2+ x/week vs 1x/week for hypertrophy.

Unless you have time constraints that force you to do otherwise, or you found through experimentation that you respond better to 1x/week training, you’d definitely benefit from training every muscle group 2+ x/week.

Note that this meta-analysis was performed on 10 studies. 8 of them were volume-equated, while 2 of them were not. This might skew the results a little in favour of high frequency (though it might make the review a little more ecologically valid, since you tend to do more volume with a higher frequency in the real world).

 

Training Frequency for Muscle Growth: What the Data Say by Greg Nuckols (2018)

Key takeaways:

  • All studies included were volume-equated, meaning that, if anything, the beneficial impact of higher training frequency on hypertrophy is underestimated in these stats, since higher frequencies are usually permissive of higher volumes.
  • Increased training frequency positively affected hypertrophy outcomes, seemingly all the way up to 6 times a week – and marginal benefits don’t appear to decrease very much as you go up in frequency, suggesting the marginal benefits might not end at 6 times/week. However, there’s not enough research investing that high a frequency to assert that with full confidence.
  • On average, each additional day of frequency per muscle group increased hypertrophy by 22%.
  • The beneficial effects of high frequency seem to be particularly potent for upper body training, low weekly volume training, untrained lifters and full-body lean body mass gains than hypertrophy of specific muscles. With that being said, significant and meaningful beneficial effects are still seen across the board for hypertrophy.

Results:

NB: This meta-analysis reviewed thirteen studies. All were volume-equated. Four of the studies used untrained subjects. The other nine used trained subjects. It included many of the recently published studies that Schoenfeld et al.’s (2016) review left out. Thus, its results differ significantly.

Benefits of higher frequency were seen in all analyses. Increases in rates of weekly hypertrophy were seen all the way up to 6 times a week. This suggests that the upper ceiling for the benefits of increased frequency could be quite high.

The largest effect sizes for high frequency training were seen, in order of decreasing magnitude:

  1. Low Volume Training
  2. Indirect Measures of Hypertrophy
  3. Untrained Lifters
  4. Upper Body Training
  5. Lower Body Training
  6. Trained Lifters
  7. Direct Measures of Hypertrophy
  8. High Volume Training

Discussion: Analytical Bias

I think a lot of people think of weekly frequency as a law of diminishing returns. The thinking goes: ” We know that if you train twice a week, you get substantially better results than if you train once a week, even when volume-equated. Since three times a week hasn’t been proven to consistently outperform two times a week (in all reviews, anyways) but there are some studies suggesting it might, that’s probably where the marginal benefits to increasing frequency ends. It’s probably a law of diminishing returns!”

The Law of Diminishing Returns as it might apply to training frequency.

 

Well, I’m not so certain of that. The law of diminishing returns is good and all, but we simply don’t have enough data to assert that training frequency follows that distribution. Moreover, there is conflicting evidence regarding frequency; Schoenfeld et al.’s (2016) meta-analysis shows no significant benefit to frequencies beyond 2x/week (I’ve heard this finding was replicated in both James Krieger’s meta-analysis and Schoenfeld’s new meta-analysis on the topic). On the other hand, Greg Nuckols’ meta-analysis suggests there are significant benefits to training more than twice per week. This might well be due to the methodological differences (Greg used direct comparisons). The point I’m trying to make is that it’s easy to make the error of letting an analytical basis arise and assert that frequency follows the Law of Diminishing Returns despite lacking the evidence to support that claim. As a reminder, these meta-analyses only had about 10-15 studies to draw from.

Long story short, due to conflicting evidence and scarcity of evidence, we just aren’t sure yet if training frequency follows the law of diminishing returns. Hence, we shouldn’t allow analytical bias to permeate our recommendations. Heck, I wouldn’t be surprised if the benefits went all the way up to 7x/week on average before plateauing. We just don’t know yet. We have some data suggesting low frequencies outperform high frequencies, while we have a bit more data suggesting that the opposite holds true.

Discussion: Type I errors

Making recommendations comes down to something Greg discusses in his meta-analysis discussion: as athletes/coaches, we ought to be relatively comfortable with making a Type I error. A type I error is a false positive – you think something is true when it isn’t. In science, as he discusses, this is a major mistake. In our case, however, I believe we should take the calculated risk of making a Type I error by training with a relatively high frequency. By doing that, we risk missing out on gains by training with low frequency. The opposite, however, is worse; there’s more data suggesting high frequencies outperform low frequencies than the opposite. Thus, I favour higher frequencies over lower frequencies.

Conclusion: My take on Frequency

This is where my opinion lies: we have mechanistic reasons (more volume, frequent stimulation of Muscle Protein Synthesis, better skill learning) to believe high frequency might outperform low frequency for both hypertrophy and strength. We also have some data suggesting that high frequency does outperform low frequency in practice, while we have very little data suggesting  the opposite. Thus, it’s more likely that high frequency will lead to better results and that’s what I go with in my own training.

Obviously, you’ll need to take into account individual response when determining the appropriate training frequency for someone. If your knees explode and you enter a state of depression when you squat everyday as opposed to twice a week.. don’t do it. If you get biceps tendinopathy and make no gains from benching only twice a week as opposed to six times a week.. stick to high frequency.

Practical recommendations:

  • Try lifting with a high(er) frequency per muscle group. At first, keep the weekly volume the same as when you trained with a lower frequency. Then, if you tolerate that level of volume and make good gains on it, but could do more, consider increasing it.
  • Conversely, if you’ve been training high frequency for a while but are getting nowhere, try reducing frequency and see how that goes.
  • Generally speaking, though, I do think high frequencies (4+) are probably better than low frequencies (1-3) – particularly for upper body training, women and perhaps low volume training.

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