Written by Sam Kelvey
Regularly wheeled out as the elixir of all strength and size gains, it is often a very important part of programme design. ‘Time Under Tension’ (TUT) denotes the amount of time a muscle is used per meaningful contraction – essentially the length of a set. Is it all it is made out to be?
We all know that to improve, a stress needs to increase. This could mean: heavier weight, more reps, more speed, bigger range of motion, more sets, tension time, or any of several other variables depending on your goal. Without this increased stress nothing changes – you simply won’t improve. How you choose to ‘stress’ your body will determine how you react – strength is a pretty specific thing.
It’s worth noting early on that TUT is not the same as ‘Tempo’, and although it might dictate the TUT of a set, it is a different and far more sketchy training variable. However, we will touch on it here briefly later on. In addition, it is very difficult (almost pointless) to measure TUT with heavy loads through low reps. With that in mind, when we use TUT it will be most effective with higher rep ranges and lower loads.
Where do we start… (deep breath)
The premise of TUT is a sound one – it is understood to be a key driver in local metabolic stress and cell swelling, which is understood to be a stimulus of muscle hypertrophy1. Commonly known as ‘the pump’; it’s often sought after by bodybuilders, but typically holds little interest for the pure strength and power athletes in their standard training, who are more interested in growing beards between sets. Put very simply, an increase in TUT for a given set (assuming the weights are the same) will mean more metabolic stress2 and so a stimulus for growth.
Taking in a little more detail, it is understood that increases in either TUT or total volume will both effectively stimulate growth, but by focusing on TUT increases, you may not see the same improvements in strength2 – and whilst muscle size is linked with strength, it is not necessarily a direct link as there are far more factors than we’ll consider here3.
In practice, using an extended eccentric (lengthening portion of a repetition) induced far more hypertrophy of Slow-Twitch fibres compared to fast-twitch, but as eccentric contractions require relatively less effort (in terms of energy and neural input)4, this could mean that the weight simply wasn’t heavy enough to stimulate the fast-twitch fibres5. So whilst it does, lend a little towards lifting ‘slowly’, the response is likely very specific – in which case you may be missing the growth of the big force-producing Type 2 fibres. This means that to focus on lifting slowly might be seen as doing half a job (if size is the goal), or missing the point (if strength is the goal).
So we see TUT can be an important variable for hypertrophy, but not necessarily for strength, and certainly not for specific strength requirements like speed or power. When considering using TUT as a guide to sessions, know that if you’re going to go slow – make it worth-while and ensure you go slowly on the way up, not just the way down – you need the burn! There is support for using low-load training (where TUT is a good measure) with those accustomed to resistance training – when pitted against traditional higher load ‘strength’ training, it has comparable improvements in size, far better increases in endurance, but is lacking in outright strength development6. For this, TUT is a great tool to ensure progress.
For special populations; those undergoing rehabilitation, elderly, physically limited, there may be more demanding use for using TUT as a defining element to training, especially when using low-loads and complemented with other methods such as occlusion training7.
To sum up: if getting massive is your thing, then working to increase TUT can be an effective way of ensuring constant overload when you’re using sub-maximal loads (think 12reps+), but obviously it is not the only way. For strength and size it can be a brilliant and useful complement to your normal training. For strength only, it’s probably not a concern in general. It won’t cure your bald patch, and bring back your goldfish from 20 years ago, but it could help you get massive.