Time Under Tension: Does Slowing Down Build More Muscle?

About a decade ago, time under tension (TUT) went mainstream, and people in gyms everywhere started lowering their dumbbells like a sleeping baby. The idea was that by slowing the rep down, you keep the muscle working longer and grow more muscle from the same weight.

While this idea has some truth to it, it got oversold, like many things in the bodybuilding world. Tension definitely matters a lot, but dragging out every rep to six seconds mostly just adds unnecessary time to your workout. Let's get to the bottom of the science on this.

What Is Time Under Tension?

Time under tension is the total time a muscle spends working during a set, adding together the lifting phase (concentric), lowering phase (eccentric), and any pauses, multiplied by your reps. So if you do 10 quick squats at two seconds per rep, that's 20 seconds of tension for your set. If you did the same 10 squats at a slow six seconds per rep, you'd have 60 seconds of TUT.

TUT is controlled mostly by tempo, written as four numbers like 3-1-1-0. This stands for three seconds lowering, one second pause at the bottom, one second lifting, and no pause at the top before going into the next rep.

Does Time Under Tension Build Muscle?

Time under tension is a factor in building muscle because mechanical tension is the main driver of muscle growth. Obviously, zero time under tension (doing absolutely nothing) builds nothing. That's not rocket surgery. The debate is mostly around whether slowing down reps more and more will build more muscle than lifting at a normal pace, and the answer is mostly no.

Research shows rep tempo doesn't have much, if any, effect on hypertrophy when other variables are the same. Even the updated ACSM position stand lists time under tension as a variable that doesn't consistently change outcomes. Slow reps do boost muscle protein synthesis in the hours after a workout, which is where the TUT hype came from, but that post-workout spike doesn't predict how much muscle you end up with months later.

In my opinion, there are two groups of people who could benefit from time under tension the most. The first is people who use body language to move their weights because a slower tempo forces the target muscle to do the work, and the second is people stuck using light weights because of sore joints or lack of access to heavier ones. Using lighter weights but lifting close to failure can build as much muscle as heavier weights, if you do it right. Slowing down your tempo can help make the most of lighter weights, within reason.

Time Under Tension vs Reps

Slowing down your set means you'll do fewer reps in that set with the same weight. Using a 5-0-3-0 tempo, for instance, significantly cuts your rep count compared to a 2-0-2-0 tempo, which means you're trading reps for more time per rep without much reason.

When researchers held total time under tension equal and had one group do 12 reps at three seconds each while the other did six reps at six seconds, both groups grew and got stronger by the same amount. Growth happens with effort and the closer you get to failure (without actually failing) regardless of how you count your sets. You can do them fast or slow, heavy or light, so long as your set gets close to failure in the muscle you are targeting (i.e. not your grip or cardio or a secondary muscle instead).

How to Use Time Under Tension in Your Training

Changing up your tempo is something you should do intentionally for a reason, rather than just slowing things down every set. Here are different ways you can incorporate more time under tension.

For strength, slow the eccentric: Lower for around four seconds to build more strength, but move the weight up with intent to produce more power. Slower lowering might increase strength, but it doesn't seem to increase muscle mass.

Keep reps between 2-8 seconds: Muscle growth will be about the same with reps taking anywhere from two to eight seconds each. Dragging your rep out past 10 seconds will give you worse results and research recommends avoiding it. When you go this slow, the weight needs to be so light that you don't get enough tension for the muscles to change (plus, it's boring).

Take sets close to failure: The weight you use should leave you with one to three reps short of failure using a controlled tempo. If your slow sets don't get you close to failure, they're not doing much. Training close to failure matters much more than the speed, regardless of how heavy or light your load is.

Use TUT for accessories: A slower tempo, like 3-1-1 works well with accessory lifts like curls, lateral raises, leg extensions, cable rows, and split squats. Using a lighter weight here lets you control through the full range of motion and you can feel the muscle better. Try it out in our full-body dumbbell workout for beginners.

When Slowing Down Backfires

If you're an athlete, you likely want to avoid doing long eccentrics on big lifts because it costs you power. Research on trained athletes found eight weeks of four second eccentric squats reduced jump height and increased sprint times. Using a two second eccentric instead improved their jumps and sprints plus increased their strength by the same amount.

Going slower just teaches your body to be slow, so if you care about athletic performance most, stick to a two second eccentric. Slower tempos also take more time, so if you're a busy person who already has a hard time getting your strength and cardio in, going slower doesn't make a whole lot of sense.

Time Under Tension Workout

Here's an upper and lower split that incorporates tempo. The tempo format is lowering, pause at bottom, lifting, pause at top, and "X" means lift as fast as you can with control. Rest for at least 90 seconds, but as long as you need to, and leave one to two reps in the tank. Do each workout twice per week and progress them by adding reps, then weight. If you can't lower with the suggested tempo, reduce your weight.

Lower Body

• Back squat: 4 x 6-8, tempo 2-0-X-0
• Romanian deadlift: 3 x 8-10, tempo 3-1-X-0
• Dumbbell split squat: 3 x 8-10 per leg, tempo 3-0-1-0
• Leg curl: 3 x 10-12, tempo 3-1-1-0
• Standing calf raise: 3 x 12-15, tempo 2-2-1-1

Upper Body

• Bench press: 4 x 6-8, tempo 2-1-X-0
• Chest-supported row: 3 x 8-10, tempo 2-0-1-2
• Overhead press: 3 x 8-10, tempo 2-0-X-0
• Cable lateral raise: 3 x 12-15, tempo 3-0-1-1
• Dumbbell curl: 3 x 10-12, tempo 3-0-1-1

Takeaway

Time under tension is part of why muscle grows, but after a certain point (a 2 second lowering phase), it's not going to do you much good to go any slower. It's important not to forget the "tension" part of the equation, which needs to be heavy enough for your muscles to feel challenged. When you go too slow, you can't lift heavy enough. It's also crucial to take every set, regardless of how heavy, fast, or slow, close to failure. Use the time you save to do another set instead.

FAQs

What are the benefits of time under tension?

Time under tension keeps the target muscle working through a full range of motion instead of letting momentum take over. A controlled lowering phase can improve strength, and a slower tempo lets you get a hard set with lighter weight, which helps in a home gym or with sore joints. It also makes form easier to feel and fix.

How does time under tension influence muscle growth?

Muscle grows when it's under enough tension to signal that it needs to adapt, so some time under tension is required. Making each rep slower doesn't add growth once the rep is already in the two to eight second range, though. Taking sets close to failure and doing enough total sets per week influences growth far more than tempo does.

What are the best exercises for time under tension?

Isolation and accessory lifts work best because the weight is light enough to control and the muscle is easy to feel. Dumbbell curls, lateral raises, leg extensions, leg curls, cable rows, and split squats all respond well to a 3-1-1 tempo. Keep big compound lifts moving with a controlled lowering and a fast lift.

Is time under tension effective for building strength?

A slower lowering phase of around three to four seconds can improve strength as well as or better than a fast drop. Heavy loads and a fast, intentional lifting phase still drive strength gains the most. Very slow reps with light weights won't make you stronger.