Slow vs Fast Reps for Muscle Growth (Science-Based)

Are Fast Reps or Slow Reps Better for Muscle Growth? You're told to go slow on the way down, but is that really true? Find out what the scientific evidence reveals about the best lifting tempo to build muscle. Time under tension may not be as important as some people think. Find out whether lifting fast or slow is better for hypertrophy.

Are faster reps or slower reps better for muscle growth? When you perform faster reps you can typically lift more weight on the other hand with slower reps you have much longer eccentric contractions which leads to more muscle breakdown. So today we're going to review what science has to say about which of these strategies is best to build muscle faster and improve your body composition    

First, we have to start with something known as repetition tempo. As the name implies, this is the actual term used by researchers to describe how fast you perform reps for a certain exercise. As I already mentioned most exercises include an eccentric phase and concentric phase. The eccentric phase refers to the portion of the movement where the target muscle lengthens. For example, your bicep is in the eccentric phase when you lower the weight during a curl. The muscle lengthens while maintaining tension to prevent the weight from going into free fall. The concentric phase refers to the phase where the target muscle shortens. For example, your bicep is in the concentric phase when you lift the weight during a curl. The muscle needs to shorten with enough force to overcome gravity. So usually you hear trainers giving the advice that you should go extra slow on the way down, and explode on the way up to optimize muscle growth. But is that actually true? 

Well in a study published in the journal of strength and conditioning research. (1) Researchers had participants perform 3 sets of 6-10 reps to failure, either with a traditional rep tempo of 1 to 2 seconds for each the concentric and eccentric contraction or they did a slow 10-second concentric followed by a slow 4-second eccentric contraction. Both groups aimed to progress as fast as they could in the amount of weight they could lift and the amount of muscle they could grow, which was measured through muscular biopsies which are considered one of the highest quality measurement methods for this type of test. At the end of the study, researchers realized that the traditional training group increased the cross-sectional area of the leg muscle fibers by 26 percent in type 1 slow-twitch fibers and 34 percent in type 2 fibers. Meanwhile, the slow tempo group only increased by 6 percent in type 1 and 15.5% in type 2. Based on those results, we can say that faster reps were better for muscle growth when compared to very slow reps.

In other studies, we look at something known as tut, which stands for time under tension, and essentially it refers to how many seconds it takes from the start to the end of your sets so it includes time for both concentric and eccentric phases. Most people believe that the longer overall time you have under tension the more muscle you will build and this is simply not true. For example, taking six seconds to do a dumbbell curl was proven to be no better for muscle growth than taking two seconds. (10) Another study found that performing reps at a fixed speed of four seconds per rep instead a naturally self-selected speed led to a decrease in both muscle activation and training volume (11) 

So does all the available research support faster reps only? Well, we have a meta-analysis (2) that evaluated eight different studies and found no statistically significant difference between repetition speed and muscle growth. With that said, when you look at the effect sizes for those studies, they do indicate that there was a trend for greater muscle growth for those training with a faster rep tempo. (3) There's a chance that the duration of the study was simply not long enough to detect a statistically significant difference between the groups. That’s why I believe this meta-analysis still indicates that faster tempos are actually better for building muscle, just as the other studies indicated. On top of that the eight studies that were reviewed in the meta analysis had many other limitations. One of those is that the studies were all performed on untrained individuals. You could question whether untrained individuals have the required exercise technique, coordination, and motivation to produce maximum muscle activation when performing an exercise faster; which by the way that's the main way that a faster tempo could increase muscle growth.

So why might faster reps be more efficient for muscle growth. Well, the first reason is that studies show slowing down your reps reduces how much weight you can lift. Meanwhile speeding up your reps can increase the number of reps that you can lift a certain weight. (4)...

[GravityTransformation]

References

1. Traditional training group increased their cross-sectional area of the leg muscle fibers by 26 percent in type 1 slow twitch fibers and 34 percent in type 2 fibers. Meanwhile, the slow tempo group only increased by 6 percent in type 1 and 15.5% in type 2.

2. 2015 meta-analysis by Brand Schoenfeld, Dan Ogborn, and James Krieger looked at a group of studies that compared fast and slow reps. When you look at the effect sizes for those studies, they do indicate that there was a trend for greater muscle growth for those training with a faster rep tempo.
(See Figure 2)

3. Studies show that slowing down your reps reduces how much weight you can lift.

4. Not only is that inferior for muscle growth, but a meta-analysis published in the journal Sports Medicine also found that it will lead to reduced strength gains

5. Performing concentric contractions explosively may increase muscle activation compared to slower reps.

6. A faster concentric may enhance strength gains.

8. Performing reps at a fixed speed of four seconds per rep instead a naturally self-selected speed led to a decrease in both muscle activation and training

[SuperStewie]

I’ve found that slow reps help me concentrate on muscle activation and proper form… and yes that means I’ve also lowered the weight, but I’ve also reduced my injuries and have seen improvements on muscles that had stagnant growth for a long time.

[moataz]

A wise man once told me in the gym, unless their technique is dangerously bad, don’t tell lifters what is right and what is wrong and what is more efficient and what is less. There are hundreds of studies that go out yearly and each one says a different thing, and often they contradict each other. What was less efficient last year may be more efficient this year and vise versa. Do whatever you see results with.

[dreamingghost]

For newbies :
- slow reps to build muscle mind connection and mouvement pattern.
- high time under tension or high reps number to build local glycogen stock and strength resistance.
For veterans :
- fast reps always focusing on the contraction of your muscle to activate it.
- slow only without concentriq with over the max weight

[CannibalShadow]

I prefer slow reps, I think the mind muscle connection is a lot better.

[arjunkb]

I think it varies from person to person. I've tried both slow reps and fast reps and for me slow reps brought more and faster muscular development when compared to fast reps.But it doesn't matter the key thing is to have a good mind-muscle connection I think that's the most important thing one should consider.

[saltrock]

Thanks for all your hard work keeping us educated. It wasn’t until I started 5x5 powerlifting routine that I notice an increase in strength and growth. Proper form is paramount especially when you’re 56 years old.

[Magneticlaw]

Fast reps can lead to sloppy form, and if momentum becomes involved the effectiveness of the exercise will decrease - things to consider. 💪

[khaiphamba]

2:41 HERE, this is all I need. "A naturally self-selected speed". Sometimes you don't need fancy advices from the PT at the gym or fancy science to get good result. Just do it the way your body feels right, grind with discipline and dedication, and you will have a lean body.

[krayzieridah]

I have never had any issues building muscle following the slow-reps routine. I like the mind-muscle connection you're getting when doing the reps slowly. For as long as I remember, I have been doing this. Controlled negatives are the way forward, at least in my experience.

[TabulaRasa]

I had always thought that if you lift weights slowly, both up and down, then the muscles work continuously throughout the whole of the reps compared to if you jerk it up and bang it down, when the muscles only work for part of the time. The rest of the time it is gravity and momentum doing the work.

[yenswan]

For me, I can fully feel my muscles contractions when doing slow reps.

[jeffrittenour]

as a 36 year old male with multiple sports-related injuries over the years, my number one priority when lifting is avoiding injury. for me that means low weight, high reps and perfect form. im not a body builder though... just a guy trying to stay lean and limber as i transition into middle age.

[Seaniekins]

For those of you looking to box, fast reps would be highly suggested considering it increases muscle activation.

[thanosmakris]

What you don't really stress out is the point of reaching to muscular failure, which is the key for hypertrophy. Slower cadence leads to failure faster and without very heavy weights and in reaching to muscular failure you will have recruited both types of fiber. But each to their own.

[jakeh]

Slow reps definitely promote better form. Especially in calisthenics. Once the form is down in your muscle memory, increase that tempo 💪🏻😉

[oparisleclerc]

Isn’t it easier to have a mind-muscle connection on slow reps? I thought that was very important

[PTLWT]

I've been doing slow eccentric, 2 second pause under tension, and explosive concentric in most my exercises for a little while now and have had good gains in muscle growth and power.

[moshehhubbard]

I prefer slow reps to make sure I properly do my reps correctly in the right form. But the key isn't how slow or fast you do it, the key is dedication and consistency👍🏾

[DTM]

One thing to watch out for with the fast contraction and free weights is when lifting "explosively", the tension on the muscle will be less as momentum carries the weight through space until gravity is able to push back down. This is why you should lift through the concentric with a speed you control and reduces the momentum of the free weight. It doesn't have to be super slow, but slow enough so you keep constant tension on the muscle. Technically, you would get a short rest with the weight traveling through the contraction until you "catch" it again. A controlled contraction is also a lot safer than lifting heavy weights quickly.