Slow Reps for Muscle Growth: Does Super Slow Training Work?

Some say that super slow training is the fastest, most effective way to make your muscles bigger and stronger.

In a traditional weight training routine, you normally take 1-2 seconds to lift a weight and a little longer than that to lower it.

With super slow training, each rep lasts somewhere between 10 and 20 seconds. One set of each exercise, and you’re done.

Fans of super slow training claim that because it puts your muscles under constant tension, you don’t need much of it to see results.

A typical workout lasts less than 30 minutes, and you do just one or two each week.

This, apparently, is all the stimulus your muscles need to grow.

It all sounds too good true, and that’s mainly because it is.

Super Slow Training: The Research

The idea that very slow lifting speeds will help you get faster results in less time than regular training seems to go in and out of fashion every few years.

And there was one paper, published back in 2001, that reports greater gains in strength with super slow compared to regular speed training [1].

In both studies described in the paper, subjects trained on a 13-exercise Nautilus machine circuit, which involved one set of 8-12 repetitions. Each rep lasted seven seconds. A second group did half as many reps, but spent twice as long on each one.

The result?

In both studies, super slow training led to a 50 percent greater increase in strength compared to regular training speeds.

However, drawing conclusions about anything based on the results of one or two studies is never a good idea, especially when most of the research out there shows that super slow training is no better than regular speed training when it comes to making your muscles bigger and stronger.

In many cases, it’s performed substantially worse.

When researchers from George Washington University Medical Center compared slow speed with traditional speed training, they found significantly greater strength gains with the latter [2].

In fact, trials conducted at the University of Wisconsin-La Crosse [3], Ohio University [4] and the University of Oklahoma [5] all show that super slow training fails to deliver faster strength gains than regular training speeds.

Super Slow Training and Muscle Growth

If you could take a closer look at a slice of muscle tissue, you’d see that it’s made up of many smaller muscle fibers.

Your muscles get bigger when those individual fibers become thicker, a process called hypertrophy.

In order for that to happen, your muscle fibers need to be both activated and stimulated for a sufficient period of time when you train.

However, research shows that muscle activation is reduced rather than increased with slow (10 seconds per rep) training speeds [6], which has a knock-on effect on muscle growth.

In one University of New England study, researchers compared traditional (1-2 seconds to lift and lower the weight) with slow speed training (10 seconds to lift the weight and 4 seconds to lower it) [7].

In the traditional speed group, muscle fiber size increased by an average of 39%, compared to an increase of just 11% in the slow speed group.

In other words, despite the big difference in time under tension, the slow speed group gained less muscle than the group using a traditional lifting speed.

A follow-up study also shows that satellite cell and myonuclear domain adaptations – both of which play a key role in muscle growth – were substantially greater with traditional compared to slow speed training [8].

In 2015, a team of US scientists published a meta-analysis on the subject of rep speed and muscle growth [9].

A meta-analysis involves pooling the results from multiple trials on the same subject. Instead of lots of small experiments, you end up with one big experiment, conducted on lots of people.

As a result, you’re left with a conclusion that’s more reliable than anything that could have been drawn from each of the smaller studies.

The researchers found no evidence to support the idea that slower reps will improve your results, concluding that “training at very slow speeds is suboptimal for maximizing gains in muscle hypertrophy.”

Research carried in the Journal of Strength and Conditioning Research also shows that super slow training has a smaller metabolic cost than traditional lifting speeds [10].

Subjects completed two workouts designed to train all the major muscle groups, one using a traditional training speed and the second using the super slow method.

The super slow workout involved one set of eight reps of each exercise, with each rep lasting 15 seconds (10 seconds to lift the weight and 5 seconds to lower it).

In the traditional workout, subjects took about two seconds to complete each rep. Both workouts lasted 29 minutes.

The result?

During and immediately after the super slow workout, subjects burned an average of 116 calories. That’s 56 calories less than they burned during the traditional workout.

When it was measured almost a day later, resting metabolic rate was no higher following the super slow workout than it was after the traditional workout.

Final Thoughts

In short, most research shows that super slow training fails to deliver superior gains in muscle size or strength compared to regular training speeds.

Taking 10-20 seconds to complete a rep may very well make your workout feel a lot harder. But it’s not going to help you get in shape any faster.