I'm a Personal Trainer — This Is Why You Should Slow Down Every Single Rep

Introduction to Time Under Tension (TUT)

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.

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.

The Science Behind Muscle Hypertrophy and Joint Health

Greater mechanical tension during the lengthening phase of an exercise can boost strength and muscle gains. 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. Research suggests total TUT for a muscle group is most relevant, and 60 seconds or more per set could be beneficial for targeting hypertrophy. Doubling the eccentric loading time compared with concentric also has positive impacts on growth.

How to Get Started with Tempo Training

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. However, the most important factor to consider in your workouts is effort and proximity to muscular failure.

The 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, 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.