Time under tension, or TUT, is the amount of time that a muscle or group of muscles is under stress. Bodybuilders get so big because they are keeping their muscles under stress for longer periods of time when lifting.
The general consensus is that increasing TUT will maximize hypertrophy.
This means that for hypertrophy it may be better for your client to lift lighter weights for a longer period of time than to use heavy weights for fewer reps.
But, this isn’t the full story. There is a lot more to the concept of TUT than simply increasing workout and lifting time.
Simply increasing total TUT may not be enough to maximize your client’s workout and to help him or her get the most hypertrophy gains.
Research suggests that paying more attention to the reps, slowing them down, and doing fewer is the more effective way to increase TUT and get the benefits.
For example, instead of powering through 15 to 20 reps for 60 seconds, have your client slow it down and do just four to six reps in 60 seconds. This will increase the window of time during which the muscles are actually under tension, therefore giving you more hypertrophy gains.
The reason that this TUT concept works may be a result of creating a hypoxic environment in the muscles being worked. Here’s how it happens:
Research has shown that hypoxic muscle environments actually enhance muscle strength and hypertrophy.4 Blood flow must be obstructed while time under tension is stressed to create a more anabolic response.
In addition to the benefits of the hypoxic environment, there is something else at work when you use TUT to achieve hypertrophy:
A muscle under stress for a longer period of time, stressed to total fatigue, will have greater muscle fiber recruitment.
The motor units in the muscle being worked are recruited from smallest to largest. The more time you keep a muscle under tension, the greater chance you have of recruiting fast twitch muscle fibers. Fast twitch muscle fibers produce more force and are larger than slow twitch muscle fibers, so more hypertrophy.1
The principles behind using TUT for hypertrophy are grounded in research, but what does that mean practically for you and your clients? Here are some strategies to try:
TUT is a concept that bodybuilders may be aware of, but it’s a tool that every trainer should have in his or her back pocket. Taking advantage of time under tension in the right way will help you help your client get to hypertrophy. When you do it right—with lighter weights, longer sets, less rest, and volitional fatigue— your client gets maximum results with shorter workouts.