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

1 Views¬∑ 01 Aug 2022
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In Sports

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.
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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)...

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