Does Slow Motion Training Actually Work?

Does Slow Motion Training Actually Work?
Lifting and lowering a bar slowly has its benefits, but what happens if ALL your exercises are done at a snail’s pace? Find out here.

This series examines legendary or popular training methods with a modern lens and an objective scientific angle. So far, we’ve covered the breathing squat 103 program and German Volume Training 125. This time around, we’ll look at a controversial approach that still has its hardcore followers: Super Slow training 12.

What is Super Slow Training?
Super Slow consists of doing resistance exercises (mostly with machines) with both a slow eccentric and concentric. The original approach used a 5-second eccentric/negative and a 10-second concentric/lifting phase. Other variations reversed that, using a 10-second eccentric and 5-second concentric. Some even went as far as doing 10 seconds per phase. In any case, the point was doing both phases of an exercise really slowly.

We must also differentiate between Super Slow as a training system and super slow as a training method. The system is when you use ONLY very slow exercises in your program. That’s what’s on trial today.

If you’re going super slow as a method, you’ll do slow reps on specific exercises or during certain training phases as a change of pace or for specific reasons (motor learning, tendon development, etc.).

But the Super Slow training system is an offshoot or a spin-off of the original HIT/Nautilus approach. To do it, you use a very low volume of training. It’s typically one set to failure per exercise and often just one exercise per muscle. It’s also a low training frequency of one or two workouts per week, performed as a circuit of 6-10 exercises.

Super Slow’s proponents claim that it’s a superior method of building muscle, optimizing athletic performance, and improving cardiovascular fitness, all while being safer than traditional lifting (1).

Let’s examine those claims!

Claim: Super Slow is Better for Muscle Growth

Proponents say Super Slow is actually superior to traditional resistance training at stimulating muscle growth.

Verdict: Empirical and scientific evidence, as well as analysis in light of the current theory of how hypertrophy is stimulated, go against that claim. Super Slow is not superior. And could even be inferior to traditional training.

Analysis: Let’s start by looking at the most up-to-date theory of how muscle growth is stimulated.

During resistance exercise, your muscle fibers produce mechanical tension. This tension is the main trigger for growth: the more tension is present, the more likely a rep is to stimulate the recruited fiber to grow.

There are two main conditions that need to be met for a rep to be maximally effective at stimulating growth:

Condition 1 – You must recruit a high number of muscle fibers, especially the growth-prone fast-twitch fibers.
You’ll only use fast-twitch fibers if you need to produce a lot of force or effort. The body always starts by recruiting the slow-twitch fibers and will gradually bring in “stronger” fibers on an as-needed basis: if the load gets heavy, if you need to accelerate a weight maximally, or as more effort is required when you fatigue during a set.

Super Slow uses low resistance and slow movements (low acceleration). That means it won’t recruit fast-twitch fibers right off the bat. The only way to end up recruiting those fibers is to reach a high level of fatigue (proximity to failure) during your set. Super Slow experts do recommend training to the point of failure. So, their sets will meet the first condition for a rep to be effective.

Condition 2 – The recruited fibers must be asked to produce a high level of mechanical tension.
Tension is related to speed of movement. The FASTER you go, the LESS tension you produce. That’s because during fast contractions, the actin-myosin cross-bridges don’t stay connected for long. So at any given time, you’ll never have a high number of active bridges at the same time. Fewer bridges = less tension.

Super Slow adepts will be happy to learn that during slower movements, you indeed get muscle fibers to create more tension. However, going slow on purpose – when you’re physically capable of moving fast because the load is light – isn’t going to be effective because the force production is low. This causes you to recruit mostly slow-twitch fibers, which have very limited growth potential.

That doesn’t mean Super Slow reps aren’t effective. It means they become effective only when the concentric is hard. For example, in a typical Super Slow set of 4-8 reps, the first 1-3 reps (depending on the load) will be too “easy” to effectively stimulate growth, the same way it is with traditional lifting (1).

That means when you reach a point of muscle failure (or one rep short) only your last 5 repetitions will be effective at stimulating growth. By that point, regardless of the load or rep style, you’ll still need to meet the two conditions required to stimulate hypertrophy.

It doesn’t matter what you do to get to that point. When you’re there, the reps you do will work. So, strictly from a set-to-set comparison, a Super Slow set will be as effective as a traditional set in stimulating growth. Not more, though. This is in line with the more modern research showing that there’s very little impact, if any, of rep speed on hypertrophy stimulation (2).

This may give you the impression that Super Slow could work. But the problem with the system isn’t the repetition style so much as it is the other training variables: low volume and low frequency.

The ideal number of effective reps (the last 5 reps of a set if you reach failure) is around 20-25 per muscle per week. Some may need more, and some may be able to progress using less (beginners might need as little as 10).

Imagine a typical Super Slow program. You’d use a traditional Nautilus machine circuit, doing 6-10 exercises, for one set to failure. If you have one exercise per muscle, that gives you 5 effective reps per muscle in a workout. If you do your Super Slow protocol twice per week, that’s 10 reps per week – significantly less than what most people need to grow at their fastest rate.

Now, some muscles might actually get all of what they need. For example, the triceps will get stimulated when you do pressing movements. So, depending on exercise selection, you might get 10-15 effective reps for triceps in a workout. The same is true for the biceps, which are stimulated properly during pulls (especially vertical pulls). Delts might also get enough due to the pressing work. But legs, back, and pecs would likely be left inadequately stimulated.

So the Super Slow rep style, strictly for hypertrophy, is fine. It can work. I would personally prefer to watch paint dry than do it, but this is an objective trial, not a subjective evaluation.

The counterpoint is that you could make Super Slow as effective as traditional training simply by increasing volume. Yes, I agree. But there’s one slight problem with that: central fatigue.

Central fatigue is a weakening of the excitatory drive from the nervous system to the muscles. The stronger the drive is, the more easily you can recruit the fast-twitch fibers. That means it will work better for gaining strength, power, speed, and size.

On the other hand, if you have a high level of central fatigue, your sets will become less effective, even if you go to failure. The biggest cause of central fatigue is the afferent signals sent from the muscles, tendons, and fascia to the nervous system. These are sent in response to pain, discomfort, level of effort, etc. Duration of exercise also plays a big role. That’s why “cardio” causes a lot of central fatigue despite a low intensity level.

Super Slow sets are likely to cause more central fatigue than traditional lifting because it’s a lot more uncomfortable and the sets are longer (80-150 seconds). You’re spending more time being uncomfortable.

Also, factor in that going to failure causes more central fatigue due to the higher level of effort required on that last rep. The short rest periods between sets and exercises also compound the problem. This means that doing more sets than the protocol recommends might not really work better because many of the sets could be performed in a state of high central fatigue.

On paper and in some studies, Super Slow seems to be as good (not better) as traditional training for muscle growth. But empirically, we don’t see many who’ve built a very muscular physique using only that approach. That might be because of the lower number of participants. But if it was effective, we’d see at least some jacked dudes singing its praises.

My main issue with Super Slow is that it’s excruciating and boring. I don’t mind suffering; I can even deal with boredom if the results are truly special and superior to less-unpleasant types of work.

But Super Slow is not superior for muscle growth. Why go through that experience, then? For the pride of hard work? To be part of an exclusive group? If that’s your thing, sure, but I thought we were after getting the most results, not getting the most fatigue and pain.