Time under tension (TUT), also known as the time under load (TUL), is the length of continuous, or at least fairly continuous, stress that the muscles handle during a set. Some experts have designed systems around monitoring and changing this parameter. Within fitness, bodybuilding, and athletic circles, the concept and how it influences the best methods for a goal gets a lot of attention.
A repetition or a rep is a complete movement of an exercise. It has a lifting and lowering phase through a range of motion. When reps group together, they form a set. A set is often defined by the number of reps performed in a row. Some methods, such as rest-pause training, allow short breaks between reps yet still count this as a single set.
Usually you establish a rep range or a set number of reps as your goal to perform on your heaviest set or sets for your strength training exercises. If you meet or exceed this, you increase the weight for the next session. This is progressive overload, the foundation of any good lifting program.
Some argue that counting reps can mislead you and foster bad habits. You emphasize outward performance instead of safety and results. They suggest measuring the time under tension instead. When you notice the yanking, jerking, and twisting that many trainees use, maybe this would help to correct those problems.
Counting reps though remains the most simple and best system. It is an example where better performance does equal a better stimulus for improvement, unlike say using support gear.
Reasons to Avoid Using Time Under Tension
Measurement is the first step that leads to control and eventually to improvement. If you can’t measure something, you can’t understand it. If you can’t understand it, you can’t control it. If you can’t control it, you can’t improve it.
– H. James Harrington
- Tension varies throughout the range of motion.
Due to the length-tension relationship, the most stimulating portion of a good exercise, the midpoint, will feel the toughest. Many trainees that measure time under tension will focus on the portions away from the middle. These positions make you feel stronger due to leverage but stimulate less growth. The sites for contraction either overlap or stretch too much.
If you do normal reps, you tend to move as quickly as needed through all portions of the exercise.
- Time under tension encourages longer sets.
We know that tension, or the squeezing of the muscles, is the main stimulus for strength and size. Other factors, such as metabolic stress that involve building up some lactate or feeling a pump, may play a small role but rank far lower than tension. Perhaps they are not worth considering much at all.
You want to avoid too long of a duration though since competing factors involved in glycolysis and the aerobic energy systems will take over as the limiting factors instead of tension. Those that monitor time under tension often have sets lasting at least a minute and well over it. Tension may suffer for these lengths.
- Time under tension generally encourages you to move too slowly.
If you move too slowly, you spend more time than you should at the endpoints of the exercise. These areas do little to stimulate tension and instead expose the joints to weak positions. A smooth but quick transition from the negative to the positive activates the pre-stretch. This boosts positive strength and in turn allows more negative work. Would it make sense to pause for long at the bottom before you explode into the air when you jump?
This also encourages a poor effort. When the weight feels heavy, you must attempt to move it as fast as possible to activate the fast-twitch muscle fibers. The intention matters more than the actual speed. Going slowly makes you less likely to exert this great effort when needed.
- Going for more reps allows the best performance.
Measuring time under tension just complicates things.
By performing as many reps as you can, you maximize your performance. Time under tension advocates assume that by trying to perform your best that you automatically expose yourself to more risk.
Good exercises, by nature, prevent you from cheating in a way to harm your joints. As long as you stay in control, you will be safe. Loose form by their standards usually just means recruiting more muscles in a natural process.
Complicating Time Under Tension
Some may state the best time under tension as 60-90 seconds. They argue this balances out all of the factors that grow a muscle. These include high tension, metabolic stress, and enough mechanical work. Others will say anything beyond 10-20 seconds recruits too much lactate. Supposedly the nervous system also stops recruiting fast-twitch muscle fibers once you stop working mostly in the ATP-PC energy system.
They may give other specifics. Use a 3-20 second time under tension for strength and 40-60 seconds for size. Longer develops endurance only.
While there is a difference between strength and endurance, no such difference exists between strength and size in the long run. The ratio of strength to size differs among trainees. Strength depends upon skills and other factors as well. These both can confuse things.
Others argue beyond 90 seconds keeps you the safest. It also gives further muscle-building benefits, perhaps a boost in growth hormone and more micro-damage to the fibers.
I personally prefer about 20-30 seconds but have had success below and far above this figure for myself and my clients.
Some argue that the lower body responds better to a longer time under tension than the upper body. Others argue that fatigue testing to determine your fast-twitch muscle fiber to slow-twitch muscle fiber ratio is important. This will then allow you to determine the optimal time under load.
This is questionable given that energy system fatigue affects everyone the same way. You just have less potential for certain activities depending on your genetic ratio.
Some argue you must vary the duration often. You need to confuse the body and keep it constantly adapting to new stresses.
This does not matter. It just changes the standards. You have to learn or relearn skills and develop other fitness characteristics with each shift. This resets the process and creates the illusion of fast progress.
Others warn you against pausing at the lockout. This resets the fatigue and makes you have to do more exercise than needed, leading to overtraining.
This is not a big deal. Short reprieves, if not taken overboard, may help mentally prepare you. It can clear out some by-products of fatigue before the last tough reps.
The Real Science Behind Time Under Tension
Experts tend to speak in absolutes. They ignore the success stories outside of the ranges that they state would cause you to fail.
Some seem to do better with more and some with less time. The reasons in favor of one or the other are endless. You need to experiment and find what time under tension, or better yet, the numbers of reps you do, works best for you. It matters far less than you may think though.
Training at or close to failure is more important than set duration. Most people will find a drop in their rate of muscle and strength gains with durations longer than 2 minutes and perhaps with even just much above a minute.
You will find that you can come to predict how much weight you could get at a given number of reps. This wouldn’t be possible if all those other factors were as important as some authorities would lead you to believe.
Avoid Dwelling on Time Under Tension
Make sure to stay in control during your reps. Move fast otherwise, especially when the reps feel difficult.
Most will do well with a moderate number of reps among 5-15. You can then modify from here based on your preference.
The energy that many put in to studying minor details will harm them in the long run. Instead of progressing in weight, getting enough quality sleep, and eating the right amount of food for their target weight, they argue and nitpick over things that matter not or very little.
Use good form, find the right number of reps for you, and realize that this ideal figure can vary. It fails to matter that much anyway.
Avoid analyzing time under tension. Focus on getting stronger by adding reps and weight over time