Time Under Tension – The best way to build muscle?

The Basics of weight training: How it works

Weight training is the best way to build muscle and strength.  Lifting weights causes the fibres in our muscles to strain and break down as they are overloaded, but because our bodies are adaptive, the muscle fibres heal in a stronger state than they were in before. The process of muscle fibres breaking and rebuilding is called hypertrophy. Increasing the load on your muscles each time you train forces your muscles to continue to adapt and subsequently strengthen and grow.

Generally, strength training involves repeating movements for each muscles known as “reps”, which ire the movement of a muscle group through a range of motion and back to its starting position, for example during a squat, one rep involves lowering your weight towards the ground and rising again.  Your muscles will respond differently depending on how many reps you carry out and the weight you use for each rep. Reps are carried out in sets, for example 10 reps make up one set before a brief rest, with each set repeated 3 times (30 reps in total).

It is important to know that muscles are made out of different types of fibres, with each type responding best to different types of training. The main fibre types are:

  • Type I fibres (Slow twitch fibres) which work by converting oxygen into energy over long periods of time – these fibres are more resistant to fatigue and move more slowly, they are the kind of fibres relied upon for strength in long distance running for example;

  • Type II fibres (Fast twitch fibres) which work quickly and fatigue quickly.

Each person’s muscles are made up of a different combination of Type I and Type II fibres which is why some people are great long distance runners, and others can lift incredibly heavy loads.

What is Time under Tension?

You may have read numerous articles and blogs about focussing in your weight training on “time under tension” or TUT. TUT refers to the amount of time your muscle spends under load during a set. Time under tension includes time spent in both the shortening and lengthening movements of a set, so the slower you carry out each rep, the more time your muscles spend under tension, or loaded.

It is generally believed that the optimum amount of time under tension in a single set should be between 30 and 60 seconds to allow optimal muscle gain. Research shows that the optimal number of reps in each set is approximately 8 to 12, depending on your strength and the weight you are loading your muscles with. Logically, the slower you carry out each rep, the closer you will get to those 8-12 reps lasting up to 60 seconds.

Time under tension can be used to vary the way in which you train each time, for example taking 3 seconds to raise a bicep curl, 2 seconds to hold at maximum contraction, and 1 second to lower the weight again. This rep places the muscle under load for a total of 6 seconds (60 seconds for 1 set of 10 reps), but different fibres are being used for the raising and lowering, so mixing up the sequence targets the muscle differently every time. Free weights are especially good to use in this process.



So How does Time under Tension work?

The idea behind TUT is that the longer your muscle is loaded the more it is working so increasing the time of each rep, or increasing the load of each rep, is believed to increase the work for your muscle and therefore the subsequent increase in strength and size.

When your muscles are loaded the blood vessels in your muscles are compressed, restricting circulation to the muscle. Research shows that intermittently starving your muscles of blood flow in this way enhances muscles growth. It is generally thought that the longer the blood supply to your muscles is restricted, the more pronounced your metabolic and anabolic response to the training, again suggesting that the longer your muscles are under load, the greater the gains you will see.

This idea is supported in a 2012 study, which found that an increase in the amount of time spent under tension for leg muscles, the more the muscles synthesised protein which leads to growth in muscle size (hypertrophy).

But is time under tension the most important focus for your training?

The jury is still out as to whether focusing on time under tension will really give you more gains in strength and size than completing your reps in a more time-efficient manner. A 2015 study found that after 8 weeks, similar increases in muscle growth in arms and legs were observed in groups of men who trained 4 sets of 10-12 reps, to those who trained 4 sets of only 3-5 reps. This could suggest that muscles do not need to be under load for a longer period of time than 3-5 reps for hypertrophy and that the total time that a certain muscle group is loaded is more important than the TUT of a set.  Hypertrophy can be achieved with heavy sets, which last a short amount of time, or with longer lighter sets, provided the muscles are being challenged.

What studies have shown, is that the longer the time under tension in a set, the greater the hypertrophy in type I muscle fibres, as these fibres fatigue at a much slower rate than type II fibres. It makes sense then that you would need to work these muscles for longer to achieve fatigue and subsequent growth. On the other hand, heavier, shorter sets are more effective for breaking down type II muscles fibres which fatigue quickly. So depending on how your body responds to weight training will indicate where your training focus should lie.

But the message is not to get too hung up on time under tension, as some studies have shown that slowing down your repetitions too much means that you cannot increase your weight, suggesting a TUT focus is less beneficial for improving performance than regular, faster repetitions.

The best way to see results is often to focus on challenging your muscles in a variety of ways to keep the body guessing and to ensure you are targeting both main types of muscle fibres. The most important thing is that you are loading your muscles correctly and focussing on your form. [may want to refer to the use of the promotion product here (10kg weight vest) here as one way in which you can increase load and challenge different muscles during a workout]

Top tips for getting the most out of each rep:

Whether you are lifting a heavy short set, or a lighter longer, slower set, these are a few tips to keep in mind to make sure you get the most out of your training:

  • You muscle fibres are under the most strain during the lowering phase (eccentric) of each rep, so lower more slowly, resisting gravity.

  • Don’t lock you muscles out at the end or top of each rep, as this allows the muscle to rest. Instead, try and keep your muscles engaged for the whole set.

  • Keep your reps at a steady tempo, whether you choose to make each set last 6 seconds, or 3 seconds, keep each one consistent.

  • Make sure you are lifting a weight that is heavy enough to cause you to be at the point of fatigue at the end of each set. Each set should get harder with the weight you have chosen, and if necessary, drop the weight down for the final set or the final few reps but keep the muscles working until the end.

  • Slowing down your reps to focus on TUT will burn! So don’t forget to breathe throughout each rep and keep the rest of your body relaxed. 

Category: Building Muscle

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