The Data Behind a Once-a-Week Strength Routine

There’s good news and bad news in a remarkable new multi-year study of nearly 15,000 people who followed an ultra-minimalist strength training plan involving just one short workout a week. The good news is that the training really works, despite taking less than 20 minutes a week all in street clothes. The bad news is that it eventually stops working, or at least gets less effective—a phenomenon that the researchers argue may be universal rather than specific to the training plan, and that has important implications for how we think about long-term training goals.

The study is posted as a preprint at SportRxiv, which means it hasn’t yet been peer-reviewed (though it is currently undergoing that process). It retroactively analyzed data from a Dutch personal training company called Fit20, whose motto (according to Google’s translation of its Twitter bio) is “personal health training in 20 minutes per week… no hassle with changing/showering.” The model has been franchised in other countries, including the United States, with locations in Florida, Virginia, Utah, and Michigan.

The training plan involves one workout a week, typically including six exercises on Nautilus One machines: chest press, pulldown, leg press, abdominal flexion, back extension, and either hip adduction or abduction. For each exercise, you do one set with a weight chosen so that you’ll reach momentary failure after four to six reps. The reps are performed slowly, taking ten seconds up and ten seconds down, without locking the limbs or resting at the top or bottom of the motion. Rest between exercises is typically about 20 seconds. The loads are adjusted from session to session to keep you failing after four to six reps. There’s no music and no mirrors.

The trainer records your loads on a tablet at every session and uploads it to a cloud-based database. This, in turn, provides a goldmine of anonymized data for resistance training researchers. The team that analyzed the data was led by James Steele, a sports scientist at Solent University and the UKActive Research Institute. He and his colleague sifted through the records of 14,690 Fit20 clients who had been training with that system for up to 6.8 years. It’s not a randomized trial, but the huge numbers and long follow-up time, along with the highly standardized training program, make it a highly unusual dataset.

There’s really just one outcome variable of interest: how much stronger did the subjects get as time passed? The paper analyzes training loads for leg press, chest press, and pulldowns. All produce pretty much the same pattern: rapid gains for about a year, then gradual gains thereafter. Here’s a representative graph showing chest press training load over the course of nearly seven years, as a percentage of the initial load:

After a year, the typical subject has gotten about 30 percent stronger. After seven years, you’re up by about 50 percent. You keep gaining, but the margins get smaller. The patterns are similar for the other exercises, though the numbers differ a bit. Leg press, for example, ends up about 70 percent higher than baseline.

There are various ways you can slice and dice the data, most obviously by considering the effects of age and sex. The subjects had an average age of 47 but spanned a wide spectrum, with a standard deviation of 12 years; 60 percent of them were female. None of it seemed to make a difference. Younger subjects tended to be stronger initially, as did males, but the rate of progress and the plateau after a year were consistent across groups.

From a public health perspective, the takeaway here seems clear: a “minimal effective dose” approach to resistance training really works. Once you reach adulthood, you typically start losing about one percent of your strength per year, with a steeper decline in your 60s and beyond. So even the plateau phase of this data, in which the subjects are making modest strength gains, represents a significant bending of the age curve. If you follow a program like this—or any program that produces similar slow-but-steady progress—you’re winning. You don’t need to feel guilty that you’re not racking up big training volumes, following sophisticated periodization plans, promoting muscle confusion, or whatever else is currently in vogue.

From the perspective of performance, the takeaways are a little murkier. Does the plateau with this training plan suggest that a similar plateau will take place with all strength training plans? That’s a risky generalization, but Steele and his colleagues point to some other hints in the literature to suggest that this may be a common occurrence. In data from powerlifting competitions, for example, progress also seems to flatten out after about a year, even though the powerlifters are presumably following far more sophisticated and rigorous periodized training plans.

One possibility is that all programs eventually produce diminishing returns, and the solution is to add a new or different stimulus. It’s certainly likely that if you plateau in one program then switch to another, you’ll see rapid initial progress in the new routine’s specific movements and challenges. But it’s less clear whether that progress is task-specific, or whether you’re actually resuming rapid gains in generalizable strength.

As for whether this minimalist approach is really enough to optimize strength gains, the question reminds me of the epidemiological data suggesting that you can get “most” of the benefits of running by doing as little as five minutes a day. That doesn’t square with the experience of competitive runners, who don’t get “mostly” race fit on five minutes a day. The key is to remember that the minimum dose for health and the optimal dose for performance are two separate questions. The new data from Fit20 offers some fascinating insights on the former question, but shouldn’t be confused with the latter.

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