Muscles and strength: The 4-second rule

Time under tension is crucial for making your muscles work according to your personal goals. Do you take it into account?

Let’s be honest: how many times have you pretended to work hard at the gym when, in reality, you relied on rudimentary physics to lift weights instead of your own muscles?

Well, that is not the best approach, and here we explain why.

Muscles: “stretch-shortening”

Unless you are a physiology student or a strength coach, you may not know what the stretch-shortening cycle is. The old term for this phenomenon is plyometrics or the plyometric effect.

The simplest way to explain it is with an example.

• Stand up (or at least imagine yourself standing).
• Bend your knees and hips as if you were going to jump, but do not jump.
• Instead, hold that bent-knee and bent-hip position for 3 to 5 seconds, and then jump.

It does not sound particularly impressive, does it? However, if you stand up and then, very quickly, drop your knees to roughly parallel without stopping, and then explode upward, you will undoubtedly get a little higher.

What you experienced when you crouched down and exploded upward was using all that elastic energy, courtesy of the natural tendency of your muscles and connective tissue to return to their most shortened state after being stretched—in other words, the stretch-shortening cycle.

The athletic world got a glimpse of the profound effect the stretch-shortening cycle has on weightlifting when Australian biomechanist Greg Wilson conducted a small experiment in the 1990s.

He discovered that if you perform a conventional bench press for your pectoral muscles, taking approximately one second to lower the bar, you need a full four-second pause at the bottom of the lift for all the energy from the stretch-shortening cycle to dissipate.

How it works in lifting

The vast majority of athletes, with the exception of professionals, cheat on almost every lift.

• In an attempt to lift as much weight as possible, they let the excessively heavy weight they chose drop toward the floor.
• Then they use the stored energy from the stretch-shortening cycle to catapult the weight upward.

That means most athletes are actually lifting a weight only a few centimeters… well, it is all a matter of knowledge, but also experimentation, so let us explain what we mean…

Two ironclad rules of lifting:

1. Lowering a weight slowly (slow eccentric contractions) emphasizes pure strength and hypertrophy in the muscles, while also placing minimal stress on the connective tissues.
2. Fast eccentric contractions harness the stretch-shortening cycle to develop strength and explosiveness.

Weightlifters mostly follow rule number 2 because they want to lift as much weight as possible.

Some athletes also use rule number 2 to develop explosive strength that could be useful in their chosen sport; CrossFit athletes also live almost exclusively in the world of the stretch-shortening cycle.

However, in the gym, a large percentage of athletes who lift weights simply try to let the weight drop and then use their connective tissues as a catapult to lift the weight for them.

In reality, they are doing very little work: by the time they raise the weight approximately two-thirds of the way, all the elastic energy from the stretch-shortening cycle has been exhausted, forcing them to do some work during only 1/3 of a full repetition.

The 4-second rule for your muscles

You have undoubtedly read many articles emphasizing either the concentric or eccentric part of the movement… coaches advocate different lifting tempos according to their athletes’ goals…

However, lost in all this discussion is the phase between lowering and lifting—the period in which you eliminate all the elastic energy and prepare to do real work, which is crucial if you want to develop muscle and pure strength.

This is where “the 4-second rule” comes in: you slow down the weight and take 2 seconds to lower the bar during a bench press.

• By doing this, you have already eliminated much of the stretch-shortening cycle, but there is still some stored energy that can be used.
• To achieve this, you then pause between the eccentric and concentric repetitions for 2 seconds: 2 seconds to lower the weight, followed by a 2-second pause, for a total of 4 seconds.
• Alternatively, you could take 3 seconds to lower the bar, after which you would only need to pause for 1 second, for a total of 4 seconds.
• You could even take 4 seconds to lower the weight and then omit the pause at the bottom entirely.

Any combination of numbers that equals 4 seconds (or more, if you wish) during the lowering phase and the subsequent pause will go a long way toward eliminating or halting the stretch-shortening cycle phenomenon and force you to perform some efficient repetitions for the benefit of your muscles.

 

The explosion of your muscles

Finally, there is one last thing you should do to make sure you are getting the most out of every repetition:

• After the pause, which dissipates the energy from the stretch-shortening cycle, you need to explode the weight upward to recruit the maximum number of muscle fibers.
• Whether you are using a lighter weight that genuinely allows you to perform the repetition faster or a heavy weight and trying to move it quickly, both recruit a large number of muscle fibers.

So explode like a rocket and accelerate like a cheetah; however, you do not need to use this 4-second rule all the time.

It can become a little boring at some point and is definitely more difficult than lifting “normal” objects, but ultimately it is a very effective way to make your muscles grow.

A recommendation: “lower the weight under control, hold the bottom position for one second, and then explode.”