Does Superslow Training Produce Superfast Muscle and Strength Gains?

superslow training

In this article, we aim to establish whether you’re missing out on superfast gains by not performing superslow training.

Traveling back to the 1980s, it’s claimed an individual named Ken Hutchins, upon conducting resistance training research on older women with fragile bones, developed superslow training.

Super slow resistance training seemed to be ideal for this demographic, as one article claims Hutchins stated “these women were so weak we were afraid for their safety”.

What Precisely Is Superslow Training?

I ran across a PDF authored by Ken Hutchins, on which he makes a distinction between superslow training as a protocol and superslow training as a philosophy. 

As a protocol, superslow training simply refers to performing exercises with a 10-second lifting duration and a 4-10-second lowering duration.

superslow training

As a philosophy, superslow training appears to be a whole training methodology. Ken notes sessions should not exceed 30 minutes, 3-7 days of rest are required between sessions, among a few other factors. 

Environmental factors are also mentioned, with Ken, quite intriguingly, believing training sessions should be devoid of music.

Other sources also state that superslow workouts typically only comprise one set per exercise.

Though superslow training seemingly has formal origins in older women, Wikipedia states, something like the superslow training was used by bodybuilders and powerlifters to break plateaus well before the 80s. 

Of course, these claims are difficult to verify.

Now, there are indeed many similarties between superslow training, Arthur Jones’ high-intensity training, and even training recommendations from other individuals such as Dr. Dough McGuff’s stuff from “Body by Science”. 

In the future, I do plan to assess these other training methodologies in more depth.

But in this article specifically, we’ll be focusing on the protocol of superslow training. That’s the 10-second lifting and 4-10-second lowering repetition tempo recommended. 

When I say superslow training from hereafter, know I’m merely referring to this repetition tempo.

So, is superslow training a superior way to develop muscle hypertrophy and strength?

Allow us to explore the existing literature. First, we’ll examine superslow training’s effectiveness for strength development, and then its effectiveness for hypertrophic adaptations. 

Superslow Training for Strength Development

A 2001 Westcott et al. study is often cited as evidence for superslow training being a potent strength-building stimulus. 

Protocol

In the paper, two studies are described.

Both studies involved just over 70 previously untrained men and women (their ages ranged from 25-82). 

They were assigned into either a superslow or regular group.

Both of these groups trained a range of nautilus machine exercises 2-3 times per week for a total of 8 weeks (in study 1) or 10 weeks (in study 2).

The exercises performed each session were the leg extension, leg curl, leg press, neck flexion, neck extension, pullover, chest press, chest crossover, lateral raise, biceps curl, and triceps extension.

The regular group, each session, performed each exercise with 1 set of 8-12 repetitions, with each repetition consisting of a 2-second lifting and 4-second lowering tempo.

The superslow group, each session, performed 1 set of 4-6 repetitions, with each repetition consisting of a 10-second lifting and 4-second lowering duration.

Both groups, throughout the study duration, attempted to gradually increase the load they used on their exercise sets within the variables prescribed to them (in other words, they progressively overloaded).

Measurements

Before and after the study, the regular group’s strength was tested via measuring the maximum load they could lift for 10 repetitions, with each repetition consisting of a 2-second lifting and 4-second lowering tempo.

Conversely, the superslow group’s strength was tested via measuring the maximum load they could lift for a single repetition, with that repetition consisting of a 10-second lifting and 4-second lowering tempo.

In study 1, these tests were done with all of the trained exercises. In study 2, these tests were done only with the chest press.

Results

In both studies, on average, the superslow group experienced greater strength gains. As noted by the authors, the superslow group saw roughly 50% more strength gains versus the regular group.

superslow training results

So, there we have it. Superslow training is optimal for evoking strength adaptations.

Not so fast.

As with all studies, limitations exist, and there is one very notable limitation.

Notable Limitation

As many of you likely noticed, the strength tests were different between both groups (in terms of repetition numbers and the repetition tempos used). 

Generally, most people think of strength as the maximum load a person can lift on an exercise without using any deliberate tempo, rather the person just attempts to lift as much as they can (this is typically called a person’s one-repetition maximum).

This begs the question: how would typical one-repetition maximum strength gains look between the superslow and regular groups?

Fortunately, another study by Keeler et al. examined this.

Protocol

14 previously untrained women (with an average age of 32) were allocated into a superslow or regular group.

Both groups trained a range of exercises 3 times per week for 10 weeks. 

The exercises performed each session were the leg extension, leg curl, leg press, bench press, seated row, biceps curl, triceps extension, and lat-pulldown.

The regular group, each session, performed each exercise for 1 set of 8-12 repetitions with an 80% one-repetition max load, with each repetition consisting of a 2-second lifting and 4-second lowering tempo.

The superslow group, each session, performed each exercise for a single set of 8-12 repetitions with a 50% one-rep max load, with each repetition consisting of a 10-second lifting and 5-second lowering tempo.

Both groups, throughout the study, attempted to increase the load they used to maintain their respective relative loading (again, an 80% one-rep max load for the regular group and a 50% one-rep max load for the superslow group).

Measurements

Before and after the study, one-repetition maximum while not using any deliberate tempo (just trying to lift the maximum weight) on all trained exercises were evaluated for both groups.

Results

For 5 of the 8 exercises, the regular group experienced much greater strength gains. For the other 3 exercises (the row, triceps extension, and biceps curl), strength gains were not statistically different between both groups. Though, it’s still worth noting the percentages still appear to favor the regular group. 

superslow training one-rep max
Data are mean

Therefore, this study indicates for increasing one-repetition maximum strength, superslow training is suboptimal.

These findings are logical. 

Superslow training, because of the very slow repetition tempos, would require you to train with relatively light loads (that is, a lower percentage of your one-repetition maximum).

This matters as the current data indicate training with heavier loads (80% one-repetition maximum or heavier) evokes greater one-repetition maximum strength gains compared to training with lighter loads.

Such findings are intuitive. If you want to increase the maximum load you can lift, training with heavy loads should promote this more than lighter loads.

As such, I think for individuals wishing to maximize their one-repetition maximum strength, simply training with heavier loads, and aiming to move them as fast as you can, is a sound recommendation.

Now, this does not mean super slow training is utterly useless for anything strength-related. Recall the Westcott et al. study found that for increasing the maximum load you can lift WHILE using a 10-second lifting and 4-second lowering tempo, training with this very tempo was extremely effective at accomplishing this. 

Consequently, if an individual wish to maximize the loads they can lift with a superslow tempo, superslow training is probably going to be the best way to accomplish this. This information may be particularly useful for those who simply cannot train with very heavy loads (due to underlying conditions or as they simply dislike heavy load training).

Superslow Training for Muscle Hypertrophy

Progressing on, is superslow training superior for muscle building?

As of right now, I’m only aware of one study by Schuenke et al. exploring this.

Protocol

19 previously untrained women (with an average age of 21) were assigned to a superslow or regular group.

Both groups trained the leg press, squat, and leg extension. Each for 3 sets, 2-3 times per week for 6 weeks.

The regular group performed each exercise set with 6-10 repetitions, using an 80-85% one-rep max load, with each repetition consisting of a 1-2-second lifting and 1-2-second lowering tempo.

The superslow group performed each exercise set with 6-10 repetitions, using a 40-60% one-rep max load, with each repetition consisting of a 10-second lifting and 4-second lowering tempo.

Both groups rested for 2 minutes between sets. Also, if subjects could perform more than their prescribed repetition numbers, loads were increased.

Results

By the end of the study, growth of fast and slow-twitch muscle fibers from the vastus lateralis (part of the quadriceps) was greater for the regular group.

superslow training hypertrophy
Data are mean

Correspondingly, this data interestingly suggests superslow training might be suboptimal for evoking hypertrophy.

Some may be thinking this is likely due to the use of the light loads (40-60% one-rep max loads) by the superslow group. However, as we’ve examined in previous articles, loads between 30% and 80% one-rep max produce similar muscle hypertrophy when repetitions are performed very close or to failure (as was more or less done in this study).

Due to this, the use of the light loads per se, by the superslow group, likely would not be sufficient to explain these results. 

So what does?

There is another potential explanation, we’ll explore this shortly.

Superslow Training = More Tension?

First, I wanted to critically examine a rationale superslow training proponents sometimes put forth as to why they believe superslow training is superior for hypertrophy.

Namely, they claim superslow training creates more tension in a muscle for a given workload.

Tension (that’s mechanical tension) is equal to the force generated by muscle fibers. 

Something called mechanosensors within muscle fibers can detect these forces and transduce them into a signaling cascade that results in muscle fiber hypetrophy.

Based on this, to maximize overall muscle growth, we’d want to recruit as many muscle fibers as possible and have them sustain fairly decent forces for a sufficient duration.

Superslow training proponents believe a superslow tempo accomplishes this best, due to the force-velocity relationship.

The force-velocity relationship states that faster muscle contractions result in less force production, while slower muscle contractions result in greater force production. 

force velocity relationship

Consequently, a superslow tempo, due to the slow muscle contraction, maximizes the amount of force a muscle can produce. Put another way, it maximizes mechanical tension and thus is superior for building muscle.

However, I believe this is a misapplication of the force-velocity relationship and is more than likely misleading. Let’s establish why I think this.

It’s essential to recognize the conditions in which the force-velocity relationship was established.

It can be established with unfatigued isolated muscle fibers contracting a single or few times at different velocities. For example, when maximally stimulating a fiber at different shortening velocities, force outcomes are in line with the force-velocity relationship.

It can also be established when comparing unfatigued muscle contractions at different forces or velocities. 

As a simple example, compare performing one rep with a 90% one-rep max load to with a 30% one-rep max load. Despite you trying to move both of these loads as fast as you can, your muscles will generate more force and contract slower against the 90% one-rep max load. This is in line with the force-velocity relationship.

However, these aforementioned conditions in which the force-velocity relationship applies are very different from lifting a constant light load to or very close to failure, and they do not mean that lifting this constant light load slowly will result in greater muscle force production. 

Henneman’s size principle helps us understand why.

Different types of muscle fibers exist within a muscle. These different types of muscle fibers can likely be categorized across a spectrum.

On one end are slow-twitch muscle fibers, which generally produce low forces but are highly fatigue resistant.

On the other end are fast-twitch muscle fibers, which generally produce high forces but are highly fatigable. 

Henneman’s size principle indicates when muscle force requirements are low, only recruitment of slower-twitch muscle fibers is necessary. But, as force requirements increase, or you near failure while attempting to sustain a given force output, those faster-twitch muscle fibers are incrementally recruited.

Here’s the thing, with a given light load, lifting it slower actually reduces the force requirements. 

Force is equal to mass multiplied by acceleration. In our case, mass mainly refers to the load used. Using a slower tempo will reduce your acceleration during a repetition, thus resulting in lower force requirements.

A study by Schilling et al. demonstrates this.  

They found when a national weightlifter performed the back squat with 170kg, using a 10-second lifting and 4-second lowering tempo produced lower mean and peak propulsive forces compared to using a maximal lifting speed.

forces with superslow training

Consequently, lifting light loads with a slower repetition will actually result in low mechanical tension initially.

However, notice I said initially. Using slower repetition tempos is not necessarily suboptimal for hypertrophy.

Recall not only do force requirements determine the number of muscle fibers recruited (as well as the force produced by recruited individual fibers), but your proximity to failure while trying to sustain a given force output does as well.

With a given light load, although using a slower repetition tempo will involve less force production compared to using a faster tempo, as you continue to perform repetitions and get closer and closer to failure, the recruitment of more muscle fibers (as well as probably increased force production by some recruited individual fibers) must occur for you to try and sustain repetitions with this given load.

As a result, regardless of whether a faster or slower repetition tempo is used, so long as repetitions are performed very close or to failure, you likely end up recruiting a similar number of muscle fibers and potentially exposing the individual recruited fibers to comparable levels of force. 

Put another way, mechanical tension likely ends up being similar.

So, to summarize this hypertrophy discussion so far, it’s very likely superslow training doesnot produce more mechanical tension. 

Rather, it’s likely so long as repetitions are performed very close or to failure, slower repetitions tempos would be similarly effective to faster repetition tempos. 

However, if this is true, why did the Schuenke study find superslow training to be suboptimal?

First and foremost, it’s worth noting this was only a single study. Also, limitations and considerations exist within it. As one example, the subjects were previously untrained women, meaning it’s not clear if the results obtained would apply to individuals outside of this demographic.

Even so, let us put forth a potential hypothesis behind why superslow training could be suboptimal for hypertrophy.

Superslow Training and Central Fatigue

As noted moments ago, it’s likely so long as repetitions are performed very close or to failure, slower repetitions tempos would be similarly effective to faster repetition tempos. 

In most cases, I believe this statement is true. For example, a meta-analysis by Schoenfeld et al. found that individual repetition tempos between 0.5 to 8 seconds produced similar muscle hypertrophy when repetitions were performed to or close to failure.

However, there might be a problem with using individual repetition tempos beyond the 8-second range (which is done with superslow training).

This problem is central fatigue.

Remember, the reason your muscles produce force is thanks to the electrical signals they receive from the central nervous system (the brain and spinal cord). 

Central fatigue refers to fatigue during exercise that decreases the number of electrical signals sent to the muscle. At the level of the muscle, this means a reduction in muscle fiber recruitment and/or a reduction in the force generated by recruited individual fibers. Put another way, central fatigue can lower mechanical tension.

Contrary to what most people seem to believe, light load and longer-lasting contractions generate more central fatigue versus higher load and shorter-lasting contractions.

As an example, Yoon et al. et al. had 9 men and 9 women, on separate days, perform a contraction of their biceps at either 20% of their maximum voluntary contraction force or 80% of their maximum voluntary contraction force. They held each contraction until force declined by 10% of the target force.

On average, subjects held the 20% contraction for around 14 minutes before they could no longer produce the required force, whereas the 80% contraction was only held for around 25 seconds.

But, the 20% contraction produced greater central fatigue than the 80% contraction.

Now, as we’ve already noted in this video, loads as light as 30% one-rep max produce similar hypertrophy to 80% one-rep max loads, when repetitions are performed very close or to failure. 

Moreover, much of these studies had subjects use a 2-4 second individual repetition tempo. Thus, we can likely conclude any central fatigue generated within these training variables does not interfere with muscle hypertrophy and is perfectly fine.

Similarly, we’ve also already noted that individual repetition tempos between 0.5 to 8 seconds are similarly effective for hypertrophy when repetitions are performed very close or to failure. In these studies, it seems mainly 50% to 80% one-rep max loads were used. Thus, we can also likely conclude any central fatigue generated within these training variables does not interfere with muscle hypertrophy and is perfectly fine.

However, and this is the key point, perhaps superslow training (due not only to the light loads but probably more so the superslow repetition tempo of 10-second lifting and 4-10 seconds of lowering that would significantly extend the set duration) ultimately evokes excessive central fatigue levels that do indeed interfere with muscle hypertrophy. 

Perhaps this explains the Schuenke study findings. 

It’s worth again emphasizing this is merely a hypothesis based on the findings of a single study. At the end of the day, future research would be needed to substantiate this.

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