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 program and German Volume Training. This time around, we’ll look at a controversial approach that still has its hardcore followers: Super Slow training.
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.
Claim: Super Slow Training Will Increase Strength
While the original Super Slow doesn’t specifically address strength, it mentions that it’s a superior method for athletic performance. Strength is part of that. So, we can assume its proponents also see it as a superior method to develop strength.
Verdict: This is unequivocally and resoundingly false. Super Slow training is inferior to strength development.
Analysis: It doesn’t take a thousand studies to know that lifting light weights won’t make you as strong as lifting heavy weights, even if the light work leads to significant muscle growth. That’s because strength isn’t just a matter of muscle mass but also how effective the nervous system is at utilizing that muscle to produce maximum force.
If more muscle mass gives you greater strength potential, you still need to maximize neurological adaptations to be able to use that potential to its fullest.
That’s what a study found when they compared light (30% of 1RM) and heavy (80% of 1RM) training to failure. While both groups had the same amount of muscle growth over the length of the study, the lightweight group only got half of the strength gains as the heavy group, again, despite the same amount of muscle growth (3).
Granted, the lightweight group didn’t use Super Slow reps, but if anything, Super Slow would lead to fewer strength gains as the force production is even lower due to the low acceleration.
What it tells us is that – surprise – if you want to gain a lot of strength, you need to lift heavy weights. Super Slow uses loads in the 30-50% range and, therefore, will not be very effective at increasing maximal strength.
Caveat: Any exercise program done with the intent to use progressively heavier loads will lead to some strength gains, including Super Slow. But the only studies showing equal or superior progress in strength from Super Slow was when the Super Slow group was tested on Super Slow tests (5RM using a Super Slow tempo). This isn’t surprising since they’re practicing that type of work.
But in studies looking at testing a true 1RM, Super Slow under-gained traditional lifting significantly. For example, researchers found that over a 10-week period with a program of 8 exercises, a Super Slow group had an average strength gain of 15% while a traditional lifting group had an average gain of 39% (4). This is pretty consistent with the light-versus-heavy study showing twice the strength gains in the “heavy” group.
For the record, when I train sport and strength athletes, I do include some slow eccentric exercises, especially in the initial accumulation phase. A slow eccentric has benefits during that phase as a preparation for the heavier lifting to come.
In fact, researchers in one study examined the rate of strength gain in lifters when they either try to accelerate the weight as much as possible (compensatory acceleration), or only push hard enough to lift the weight, leading to a slower rep speed.
The group trying to accelerate as much as possible had almost twice the strength gains as the group going slower (5). While this study didn’t delve into Super Slow per se, it does indicate that trying to accelerate a load is more effective for strength than going slower.
It’s very effective at speeding up motor learning and could help develop tendons and technical efficiency. This is important stuff when you move on to a phase of heavy, traditional lifting. But I never use slow concentric phases like Super Slow recommends, at least not on the lifts where I want to develop maximal strength.
Claim: Super Slow Training Improves Cardiovascular Fitness
The belief is that Super Slow training is as effective (or more) as aerobic training to improve cardiovascular fitness. Writing on the original Super Slow work is very anti-aerobic. It asserts that aerobic work is actually dangerous and that Super Slow training is just as effective as aerobic training in improving cardiovascular fitness.
Verdict: This is laughable, at best. Many studies have found no improvements in cardiovascular capacity from Super Slow exercise. Although if done in a circuit format, it can have some positive effects. However, a Super Slow circuit wouldn’t be any more beneficial in this regard than traditional circuit training.
Analysis: Circuit training can have a positive impact on many cardiovascular fitness markers. It can improve VO2 max and mitochondrial density, as well as several other health markers. But those benefits are due to the structure of the workout (circuit), not the repetition style.
In fact, a Super Slow protocol was shown to have no significant improvement in VO2 max over a 16-week period (6). A different, short-term study did find a very small improvement in VO2 max with a Super Slow protocol, but not any different than the traditional training group involved in the study (7).
The Keller study mentioned earlier also looked at VO2 max improvements and found no difference between a Super Slow protocol and a traditional lifting approach, although both groups had a small improvement.
What this shows is that the speed of the reps doesn’t have an impact on cardiovascular fitness development. The modest improvements are from the circuit structure. And these improvements are much lower than they would be with aerobic training.
Claim: Super Slow Improves Athletic Performance, Power, and Speed
The belief is that Super Slow training is superior and safer than traditional lifting for improving athletic performance.
Verdict: Whiskey Tango Foxtrot! Not even close.
Here, the literature is pretty straightforward: strength increases are velocity-specific. You get better at fast movements by training fast movements. For one thing, the motor recruitment pattern is different between fast and slow movements.
During fast/explosive movements (on the left) there’s an initial burst from the agonist/prime movers (and synergists) while the antagonist (muscles opposing the movement) are relaxed. The more relaxed they can be, the more explosive you will be. Then the antagonist(s) fire to stabilize the movement and allow the agonists to provide a second burst. This all happens in milliseconds.
During slow-strength movements (on the right), there’s only one activation phase: the agonists fire all the way through, with a background co-activation of the antagonists. This is because, during explosive movements, the brain favors speed over stability. During slow movements, it’s the opposite.
So, you can be really good and strong in slow movements without improving fast movements. And vice versa.
If you train exclusively using slow movements, you won’t be able to improve fast movements as much as if you included traditional training as well as high-velocity work (jumps, throws, explosive lifting, and Olympic lift variations).
Most sports require fast movements. Draw your own conclusions.
Super Slow Training: The Final Verdict
Super Slow as a training system:
- Can be effective as a hypertrophy approach but isn’t superior to traditional training. And progression is pretty much limited to adding weight because this type of work might cause too much central fatigue to be able to add volume as a means of progression.
- Is inferior for strength gains unless we’re talking about strength during super slow movements. But if we’re talking about absolute strength – as in the most weight you can lift – Super Slow is not close to traditional training.
- Has moderate effects on cardiovascular fitness due to the circuit nature of the program. But the cardiovascular effects aren’t close to aerobic training and are not superior to circuit training done with a traditional rep style.
- Is vastly inferior for athletic performance if the sport is centered around explosive movements.
If you’re only interested in building muscle and being healthier, it’s an acceptable approach, especially if you use it as a change of pace from traditional training. But I find that few people will be able to stay with it for the long run. The main problem? You’ll be stuck with more or less the same plan because you can’t really add volume with this approach, and you use a limited exercise selection. Not to mention, it’s not a practical approach in a commercial gym where doing a circuit of 6-10 machines might not be possible.
If you want strength, speed, or power, then it’s definitely not the approach for you, at least not as an exclusive training system. It’s possible, however, to add some slow eccentric work to a traditional lifting program for some specific purposes.
I’m not sold on it.
- Hutchins K. Super Slow: The Ultimate Exercise Protocol (2nd ed.). Casselberry, FL: Media Support, 1992.
- Schoenfeld BJ et al. Effect of Repetition Duration During Resistance Training on Muscle Hypertrophy: A Systematic Review and Meta-Analysis. Sports Med 45, 577–585 (2015).
- Cameron CJ et al. Resistance exercise load does not determine training-mediated hypertrophic gains in young men. J Appl Physiol (1985). 2012 Jul;113(1):71-7.
- Keeler LK et al. Early-Phase Adaptations of Traditional-Speed vs. Super Slow Resistance Training on Strength and Aerobic Capacity in Sedentary Individuals. Journal of Strength and Conditioning Research 15(3):309-314, August 2001.
- González-Badillo JJ et al. Maximal intended velocity training induces greater gains in bench press performance than deliberately slower half-velocity training. Eur J Sport Sci. 2014;14(8):772-81.
- Blount PA et al. The effect of Super Slow training on strength parameters in college aged males. Med. Sci. Sports Exerc. 35(Suppl. 5):S373. 2003.
- Kim E et al. Effects of 4 Weeks of Traditional Resistance Training vs. Super Slow Strength Training on Early Phase Adaptations in Strength, Flexibility, and Aerobic Capacity in College-Aged Women. Journal of Strength and Conditioning Research 25(11):3006-3013, November 2011.