One training technique I have employed in the wake of several small injuries is to increase my time-under-tension, and I have done so with incredible results! First, I’d like to fully break down and explain what time under tension is, and then I would like to delve into why it is a critical component of muscle growth, and then finally, how you can increase your time under tension during your workouts to maximize your results.

Time under tension, in its simplest definition, is the time that your muscle spends under load during a set. This includes the time spent in the concentric (shortening) phase, peak contraction phase, and eccentric (lengthening) phase. So, if you perform a 10 rep set, and each rep takes you 3 seconds to complete, your muscle experienced 30 seconds of time-under-tension.

If you were to perform that same set, this time, however, taking 2 seconds to lift the weight (concentric phase), 1-second pause during peak contraction, and 3 seconds to lower the weight (eccentric phase), those same 10 reps would take you approximately 60 seconds. As you can see, even though the rep count has stayed the same, the muscle spent significantly more time under tension in this set than in the set taking 3 seconds per repetition and subsequently has performed a lot more work. How can this be if the reps performed were the same, you ask?

Your muscles can’t count, that’s why! I know that sounds like the answer to a terrible joke, but the concept behind it is one that can’t be ignored! Muscles don’t know you re lifting a 30-pound dumbbell for 10 reps; they simply feel the load created by the weight and the mechanical tension that comes from contracting the muscle under the aforementioned load. Logically then, the two ways to increase the work done by your muscles are to increase the load or increase the time the muscle is placed under this load and forced to contract. This is going to be no surprise to most reading this article, as it is a very well know fact that progressively overloading one’s muscles will force them to adapt, and subsequently grow. This adaptation comes from your body replenishing and fixing the protein degradation and microtrauma caused by exercise.

So the question begs, what is the optimal amount of load, and time under tension of this load, you should subject your muscles to in order to achieve maximum muscle growth, as well as maximum protein synthesis and tissue repair? Research has proven time and time again that the optimal rep range for muscular growth, or hypertrophy, is between 8 and 12 reps. Like we just discussed though, your muscles can’t count, so that rep range is more indicative of the appropriate time under tension for maximum muscle growth. So the question that begs to be asked is not what the optimal number of reps for muscle growth, but instead, what the optimal range of time under tension for hypertrophy?

Charles Poliquin was/is one of the leaders in pioneering training that focused on manipulating time under tension. Through his experience and research, he was able to develop optimal ranges of time under tension depending on your goals. The range he found to be most beneficial for muscular hypertrophy is 30-70 seconds per set, with 30-50 seconds providing more “functional hypertrophy”, or training that with emphasize both strength and size gains, and 50-70 seconds providing maximum hypertrophy with less focus on strength gains. Armed with this knowledge, one can logically assume that performing sets of 8-12 reps, with each repetition taking between 4-6 seconds, will maximize muscular hypertrophy.

Several researchers recently performed a very interesting study to examine the effects of increased time under tension with respect to protein synthesis, which is a major indicator of muscle growth. In this study, 8 males who had been training legs with some type of resistance based exercise 2 times per week, for at least 2 years, performed 3 sets of unilateral (one leg at a time) leg extensions using 30% of their 1RM. With one leg, the set was performed with 6-second concentric and 6-second eccentric actions to failure. With the other leg, they performed a work-matched set with 1 second concentric and 1-second eccentric actions. Needle biopsies of the muscle tissue of both legs were taken at rest, 6 hours, 24 hours, and 30 hours post-exercise. The results between the two methods were startling: Exercise-induced rates of mitochondrial and sarcoplasmic protein synthesis were elevated by 114% and 77%, respectively, above rest at 0–6 h post-exercise only in the SLOW condition. Mitochondrial protein synthesis rates were elevated above rest during 24–30 h recovery in the SLOW (175%) and CTL (126%) conditions. Based on these results, one can infer that increased time under tension leads not only to increased muscle protein synthesis but also brings the onset of this increased synthesis quicker.

To summarize, increasing time under tension will do two things that lead to increased muscle growth:
1) Increase protein synthesis
2) Increase micro-trauma to the muscle

TECHNIQUES TO INCREASE YOUR TIME UNDER TENSION

1.  ALTERED TEMPO

The first and most logical way of increasing your time under tension is to increase the length of your reps. What portions of the lift should be slowed down, and what portions should remain normal speed? You are able to create the most micro-traumas during the eccentric part (lowering/ lengthening part) of the exercise, so it is key to spend enough time lowering the weight to reap the maximum benefit. In my experience, I’ve had the most success using approximately 3 seconds to complete the eccentric component of my lift.

Once at the bottom of the rep, I am a firm believer in the use of a slight pause (a second or so) for a couple reasons. First, it removes all momentum and stored energy from your body, meaning that when you begin the concentric portion of the lift, you are receiving no extra help. Second is that the pause truly gives you a moment to prepare to activate the muscle for the concentric portion of the lift. This increased awareness, or mind-muscle connection, allows one to recruit maximal muscle fibers, which will lead to expedited results.

When beginning the concentric portion of an exercise, it is paramount that you focus on being powerful and explosive, but still keeping perfect form. This part of the lift should take no longer than about 1 second, or slightly longer as your body fatigues. Once at the top of the rep, on can create maximal tension by pausing for a second under full contraction. Doing so will both increase your time under tension, and recruit maximum muscle fibers.

So, to sum it up, my recommended change to your tempo when aiming to increase time under tension is 3-4 seconds eccentric phase, 1-second pause, followed by performing the concentric portion as quickly as possible while maintaining form. This tempo works out to be approximately 5-6 seconds per rep, which is a perfect tempo when aiming to perform 8-12 reps, and be under tension for 30-70 seconds.

2.  DROP SETS

Another great technique for increasing your time under tension is performing drop sets. To perform a drop set, you lift a selected weight until you reach the point of failure, and then lighten the weight, and continue lifting until a predetermined amount of reps are performed, or you reach failure again. When employing this technique to increase your time under tension, I recommend selecting a weight you can perform 4-6 times before reaching failure, followed by a weight you can perform 10-12 times before reaching failure. Doing drop sets in this manner will subject your body to heavier poundage’s necessary for maximal tissue breakdown, while still keeping the muscle under tension for the optimum amount of time.

3.  PARTIAL REPS & FORCED REPS

Partial reps and forced reps are a great way to be able to increase the weight used, while still staying in the optimal time under tension range for muscle growth. Partial reps are reps that are performed in a manner that you don’t fully lockout any joints (on pressing motions) or don’t reach peak contraction (on pulling motions). Performing reps shy of completion keeps constant tension on the muscle and allows for you to handle weights that are heavier than you would if you were using strict form and a slower tempo. Forced reps are reps in which a spotter assists you past the point of failure, and allows you to continue performing repetitions. This technique also extends the time spent under tension, while allowing for heavier weights to be used. Forced reps are very strenuous on your muscles, tendons, and nervous system though, so be sure to use them sparingly.

In conclusion, I think the amount of time you are putting your muscles under tension for is a critical component of maximizing muscle growth, and anyone would benefit from mixing some increased time under tension into your current program. Not only will the increase in time under tension spur new muscle growth, but it will force you to check your form and use more appropriate weights. So my challenge to you is to increase the time under tension you experience during your training program, and reap the rewards! As always, if you have any questions, don’t hesitate to leave it in the comments or send me a message, ill do my best to answer in a timely matter!

REFERENCES

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3285070/