Everyone wants to get in shape, but many of us lack the time or patience to get results, especially if our goal is to build a more muscular physique. Although there are plenty of tips online telling people the best ways to do this, not all information is reliable or backed by evidence. A suggestion often made by fitness enthusiasts is a training method called “time under tension”. It’s the idea that slowing down the pace of your exercises — like your squat or your bicep curls — is the secret to helping you get stronger faster.
Simply put, time under tension refers to how long a muscle is working during a certain exercise. For example, if you were doing push-ups, you could aim to take two seconds on the way down, then two seconds on the push-up from the floor – meaning you’re keeping the muscle under more tension (theoretically working harder) than if you had to rush into your pumps. So if you did ten pushups, it would take you about 40 seconds to complete one set.
Proponents of time under tension claim that by maintaining longer periods of muscle tension — typically 40-60 seconds per set — you’re more likely to experience muscle growth. This sounds great in theory, but in practice it’s not that simple.
The Bodybuilding Equation
To build muscle, training volume is the most important factor. This is the total amount of weight lifted throughout the workout. So, for example, if you do four sets of a barbell squat and perform eight reps each set while lifting 100 kg, your overall training volume for that exercise would be 3,200 kg. However, the number of muscle fibers we recruit during an exercise (which depends on the amount of force needed to perform an exercise or lift a weight) is also important.
Blood flow also plays an important role in muscle growth. When our muscles contract during a resistance training exercise, the blood vessels that supply the working muscles compress. This reduces circulation to the muscle, temporarily preventing enough oxygen reaching the muscle (known as hypoxia). Although we don’t know exactly why, we do know that hypoxia leads to increased muscle growth, and that prolonged exercise under tension reduces blood supply to the muscles for longer periods of time. This is why many people believe that longer time under tension will lead to greater muscle growth.
However, research tells a different story.
Studies have repeatedly shown that slowing down the pace of a movement or motion has no more muscle-building benefits than lifting at a steady or even fast pace. This is true if the workout is for the the whole bodybased on compound lifts (exercises that engage multiple muscle groups at once, such as a back squat), or using resistance devices.
In fact, some research has even suggested that while no difference in muscle growth is achieved at slower speeds, muscle fiber activation, overall training volume, and even strength gains are all inferior in people who train at a slower pace – rather than their natural pace.
Waste of time?
But that doesn’t mean we should dismiss the role of time under tension entirely. Although research suggests that overall muscle growth may not be better than exercising at a normal pace, spending more time under tension (about 60-90 seconds per set) may lead to greater muscle growth in muscle fibers specific.
Our muscles are made up of different types of muscle fibers. One of them is made up of slow-twitch muscle fibers (called type I fibers), which are important for endurance because they don’t tire as quickly as other muscle fibers. This makes them essential for activities like long runs or bike rides, high-rep sets, or isometric holds (like the plank).
Short durations of exercise with very heavy weights are unlikely to fatigue our slow-twitch muscle fibers. But research shows that time under tension can help us better develop these important muscle fibers.
Of course, many of us aren’t very experienced weightlifters or bodybuilders, but time under tension can still benefit us – and can also be a great starting point for people, especially if they don’t have never lifted heavy weights before. In fact, in clinical exercise contexts, we use time under tension as a way to reinforce good technique. This helps reduce the risk of injury and helps people learn how to optimally recruit their muscles.
All in all, there’s no real “hack” to building muscle, despite what tension-time proponents may claim. If you want to build muscle, it takes consistency, good nutrition, and trying to challenge yourself in every workout by doing a little more or lifting a little heavier.