I’m a personal trainer — this is why you should slow down every single rep

If you haven’t heard of a weightlifting technique called time under tension, let me introduce it. This approach slows reps of an exercise, typically during the eccentric phase (like lowering into a squat), but sometimes during the concentric phase (like standing from a squat), too.

In short, it refers to how long muscles spend activated, loaded or under contraction. If you increase the overall volume of tension held in muscle groups, whether that’s using weights or not, you can stimulate hypertrophy (muscle growth) because the muscles meet resistance longer, which can help build muscle without lifting heavier weights.

If you’re considering adding the TUT technique to your strength training program, I cover everything you need to know below.

Does time under tension actually work?

Thankfully, time under tension isn’t a myth you’d find from fitfluencers on TikTok; it works.

Slowing a move down means performing it for longer, demanding more from your muscles to keep your form in check and work through the reps. The technique is popular in Pilates, too, which involves high-rep endurance training. If you’ve ever been in a Pilates or yoga class, you’ll know that when you slow exercises in either one or all phases, they feel much harder and require more muscular control and stability.

Back when I was training to become a personal trainer, we learned to program exercises in three stages: the concentric phase (when muscles shorten or contract under load), the eccentric phase (when the muscle lengthens), and the pause between them, or isometric contraction.

You may notice trainers now program a lot with eccentric training, or working in negatives, which has become a popular method for growing muscle. Because it’s the braking phase of a motion and you have a higher force capacity in this phase, slowing it down by three to five seconds per rep has a few potential benefits.

You can also pause for longer during isometric contraction — placing the muscle under stress without shortening or lengthening.

Greater mechanical tension during the lengthening phase of an exercise can boost strength and muscle gains, according to research. Focusing on time under tension during the eccentric phase can also help prevent injury by training your braking forces, meaning stronger tendons and ligaments, too, which is crucial for age-related muscle loss and joint problems.

Pilates teachers often adopt both eccentric and concentric tempo training, but you’ll typically find the concentric phase (when your muscles meet the most resistance) shorter and more powerful.

That said, research published in Science and Development of Muscle Hypertrophy suggests total TUT for a muscle group is most relevant, and 60 seconds or more per set could be “beneficial for targeting hypertrophy.”

Another 2016 study found that doubling the eccentric loading time compared with concentric had positive impacts on growth. But before you change up your training, make sure you lift weights with good form and focus on the correct range of motion as a priority. If you can’t complete a rep because you’ve slowed it down, consider a lighter weight or a shorter working set and build slowly.

How to get started

In theory, you can take your program and start slowing your reps down. This might mean opting for different weights or rep and set ranges to begin with. Start by following your strength training program with 35-60 seconds on each set.

For example, if you timed a bench press at a 4-1-4-1 tempo for six reps per set, you’d hit 54 seconds. The last few reps of each set should be tough to finish.

Another popular method is a complex, which involves grouping exercises into a sequence that builds out your overall volume. By grouping exercises into one long working set, you can reach the same goal. This five-move barbell complex is a great place to start.

But remember, the most important factor to consider in your workouts is effort and proximity to muscular failure. This is what will move the needle most if your goal is to build strength and/or muscle. Those reps need to feel very challenging. If you can easily pump out more than two or three reps over your target reps per set, tempo training or not, you may need to add more load or reps.

Verdict

I personally love slowing reps down, and we know that time under tension can help build muscle. However, I want you to remember that protein, sleep, recovery, progressive overload (building volume over time) and consistent training all matter when your goal is to build or maintain strength and muscle.

If you’re not doing the basics, fancy tempo training won’t change the game.

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Sam Hopes is a level 3 qualified trainer, a level 2 Reiki practitioner and fitness editor at Tom’s Guide. She is also currently undertaking her Yoga For Athletes training course.

Sam has written for various fitness brands and websites over the years and has experience across brands at Future, such as Live Science, Fit&Well, Coach, and T3.

Having coached at fitness studios like F45 and Virgin Active and taken on both 1:1 and group, Sam now primarily teaches outdoor bootcamps, bodyweight, and kettlebells.

She also coaches mobility and flexibility classes several times a week.

Sam has completed two mixed doubles Hyrox competitions in London and the Netherlands and finished her first doubles attempt in 1:11.