Time Under Tension: the Stimulus for All Muscle Growth

Time Under Tension: the Stimulus for All Muscle Growth

What makes muscles grow? You might say progressive overload, exposing muscles to greater demands than they’re accustomed to but, ultimately, it all comes down to subjecting your muscles to force. In turn, force is linked with how much “tension” you apply to the muscle. Tension on a muscle leads to muscle damage, the stimulus your muscles need to grow.

You’ve may have heard about “time under tension” and how it relates to muscle hypertrophy. If you force a muscle to work against a challenging resistance, it won’t grow if the duration of the stimulus is too short. That’s where the time element comes in. You need to keep the muscle under tension for a certain amount of time to sustain enough muscle damage to elicit growth.

What Exactly is Time Under Tension and How Can You Modify It?

Time under tension refers to the length of time a muscle is under tension. For example, if you do a biceps curl allotting 3 seconds for the concentric phase (lifting the weight towards your chest), 1-second pause at the top, and 2 seconds for the eccentric phase (lower the weight back down), the cadence would be 3-1-2. Now suppose you slow the cadence down to 6-1-5 and do the same number of reps, you’ve doubled the time under tension. Even if you haven’t increased the resistance you’ve subjected your muscles to more tension and created more muscle damage.

Most people get into the mindset of increasing the resistance or weight used for a particular exercise. That’s one way to build strength and promote muscle growth, but it’s not the only way. You can also keep the resistance the same and increase time under tension by slowing down the cadence of your reps. That’s the idea behind super-slow training, a resistance training approach popularized in the early 1980s.

Most people use a cadence of 2-1-4, 2 seconds concentric, 1-second pause, 4 seconds eccentric. Super-slow training extends the length of the concentric and eccentric phases by using a cadence of 10-1-5, although some forms of super-slow training use a cadence of 10-0-10. Extending the length of the concentric and eccentric phases increases the time your muscles are under tension and the amount of growth-inducing damage they sustain.

 Why More Time under Tension Stimulates Muscle Growth

How does increasing time under tension boost muscle growth? Because your muscles are held under tension for a longer time period using a slow cadence, more muscle fibers have to be recruited to maintain that tension. As a result, muscles receive more stimulation to grow.

In addition, keeping a muscle under tension longer leads to greater accumulation of lactic acid. Lactic acid build-up stimulates the release of growth hormone, an anabolic hormone that enhances muscle protein synthesis. Your muscles will also look a bit fuller after doing a super-slow routine since the increased time under tension boosts sarcoplasmic hypertrophy, an increase in the volume of the non-contractile or fluid portion of the muscle. More time under tension also increases energy expenditure, so you get a little extra calorie burn.

Another advantage of super-slow training is it almost completely eliminates momentum and “cheating.” You can really focus in on your form when you slow down the cadence enough.

Use Super-Slow Training Judiciously

As you can see, super-slow training offers a different approach to stimulating muscle growth. It’s an effective way to increase time under tension, but it’s also demanding on your muscles and your nervous system.  Unlike traditional resistance training where you do multiple sets, with super-slow training, one set to complete fatigue is enough due to the taxing nature of this type of training.

Don’t use this technique every time you train. One or two super-slow sessions a week is enough to get the benefits without overtraining. You can even incorporate a few super-slow sets into your regular workout for variety. Don’t forget about the importance of “changing things up.” Ultimately, you want to use a variety of rep cadences and advanced training techniques like partial reps, supersets, pyramiding, drop sets, etc. Don’t let your muscles get too “comfortable” by establishing an unchanging routine. Modify your routine regularly or periodize it to expose your muscles to varying levels of stimulation.

Another Way to Increase Time under Tension

Slowing down the tempo of reps is only one way to increase time under tension. You can also increase the total number of reps you do, but when you significantly increase the number of reps, you usually have to use a lighter weight. If you lighten the weight and increase the number of reps beyond a certain point, you’re mainly building muscle endurance.

The tension placed on a muscle varies over the course of the exercise. For example, when you do a squat, the tension is low at the beginning of the movement and gradually increases until you reach the lowest point in the squat. As you rise from the squat, the tension gradually drops off again. Ideally, you want the tension to be high throughout the entire range-of-motion of the exercise, which usually isn’t the case. With super-slow training, you keep the tension higher longer by slowing down the rep cadence.

 Is Super-Slow Training Superior for Muscle Growth?

Some studies show super-slow training is better than using traditional rep cadences while others suggest that it’s no better than standard weight training for muscle hypertrophy or strength gains. What super-slow training can do is “jumpstart” muscle hypertrophy when you’ve reached a plateau. Use it to diversify your workouts and give your muscles an added stimulus to grow.



T Nation. “Create Tension, Build More Muscle”

J Physiol. 2012 Jan 15; 590(Pt 2): 351-362.

Super Slow Resistance Training. Jeff Nelson, M.Ed. and Len Kravitz, Ph.D.

Poliquin. “Ten Things You Should Know about Tempo Training”

“The effect of time-under-tension and weight lifting cadence on aerobic, anaerobic, and recovery energy expenditures: 3 submaximal sets” Christopher B. Scott.

J Strength Cond Res. 2003 Feb;17(1):76-81.

Journal of Sports Medicine and Physical Fitness. 41: 154-158, 2001.


Related Articles By Cathe:

Get Stronger and Break Through Plateaus with Explosive Training

What Role Does Mechanical Tension Play in Muscle Hypertrophy?

How Often Should You Change Your Strength Training Routine?

Horizontal vs. Vertical Loading in Weight Training: What Are the Advantages of Each Approach?

Muscle Hypertrophy: 3 Ways in Which Muscles Grow

Is Muscle Damage Necessary for Muscle Growth?

Is Muscle Soreness Correlated with Muscle Growth?


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