You’ve got hidden strength you may not even know about – but worry not, reader, for I am about to hand you the keys to lift heavier and burn more fat, while at the same time reducing the chance you’ll get injured while lifting.

Once Upon a Time…

First, we have to cover a little bit of science before we get to the good stuff, so bear with me because it will all come together nicely in the end.

Our journey begins about a hundred years ago when Nobel Prize winning neuroscientist Sir Charles Scott Sherrington developed what have come to be known as Sherrington’s Laws. The particular law we are interested in is his law of muscular irradiation.

Muscular what? I don’t want radiation in my muscle! Hang on there pal, let me explain.

Because, Science

Whenever we use our muscles, whether to lift a heavy ass weight or to pull away from the prick of a sharp object, our brain and nervous system are in the background running the show automatically, adjusting movement within split seconds.

Nerves are like wires that connect every single muscle in your body to the central nervous system (CNS) and brain. They extend throughout our entire body and send neural impulses (signals) to our muscles in order to activate them and generate force.

When muscle fibers slide over each other, a high level of tension is created which in turn allows us to move our body and external loads, or in our case weights/kettlebells. (We’re almost there friends, stay with me.)

Nerves that wire together, fire together. So if you want to, say, deadlift a weight off the ground, it makes sense to flex the muscles in your legs while pulling said weight off the floor. If you wanted to press something overhead, you’d flex the muscles in your upper body.

Over time, aside from laying down new layers of muscle, we also get stronger in part because our body learns how to use this pathway of nerves to activate the muscles needed to lift the weight. This is how we get stronger and better at different exercises over time.

So, strength is expressed by creating tension in our muscles and in turn our muscles generate force to produce movement. Tension = Force.

However, the catch is that in order for your CNS to recruit the maximum number of muscle fibers, it needs to feel stable. If you’ve ever done a plank on a physio ball, you have experienced firsthand how difficult it is to generate force while remaining stable versus planking on the ground where you can easily hold still. You shake because the unstable surface won’t allow full force production.

Our bodies are smarter than we are and these safety mechanisms are built in to prevent injuries like ripping a tendon off a bone because you got a little over zealous on a lift while your favorite Katy Perry song blasted through the speakers.

By increasing tension, your CNS will feel stable and safe enough to produce force.

Key Takeaway

Strength is your ability to generate force. The more tension you create, the more force you will produce. This is all controlled by your nervous system, and you’ll be stronger if you can convince your body that you are stable.

Whew. That was a mouthful. Still with me? Practical examples coming up!

Start Your Engines

Sherrigton’s Law of Irradiation states: “A muscle working hard recruits the neighboring muscles, and if they are already part of the action, it amplifies their strength. The neural impulses emitted by the contracting muscle reach other muscles and ‘turn them on’ as an electric current starts a motor.”

Pretend you had to punch through a thin wall. Go ahead and make a fist but only squeeze your hand/fingers and nothing else. Pretty weak fist right? Now squeeze a little bit harder. You may feel your forearms tense a little. Now make a tight fist and squeeze your forearms as well, now we’re talking a decently strong fist. Finally, squeeze your fist, forearms and flex your upper arm, even include your shoulder. I bet you could easily punch through a wall now (don’t actually punch a wall, we can’t be liable for repairs or damages to your knuckles). This is an example of muscular irradiation.

In practice, the more muscles you tense, the louder the signal your nervous system is sending out and the stronger you’ll be when you lift! By combining the contractions of nearby muscles, you’ll generate more force.

Now, you’re probably already doing this to some extent via your own instincts. You may brace your abs or your back when you bend down to pick up a heavy box or flex your shoulders and arms when pushing through a heavier than usual revolving door.

Ok So How Do I Do This Irradiation Thing?

For the majority of movements, you can’t go wrong by making sure you are actively squeezing whatever implement you are using (barbell, dumbbell or kettlebell). Next, flex or tense the intended muscles being used in the exercise. As a bonus, lock your rib cage down, keep your abs and butt tight for added stability. Here is a way to put this into practice:

Example: Bent Over Row with Kettlebell

1. Crush grip the bell and tense your hamstrings and glutes to increase your lower back/hip stability. You may want to make a tight fist with the non-working hand if doing single-sided movements.
2. Brace your abs, chest, and squeeze your mid and upper back to keep everything tight and call all muscles on deck!
3. Think about what muscles are causing movement and how you can keep those muscles engaged and tight along with surrounding muscles.

Music to Your Muscles

Our CNS is really efficient at establishing neural pathways and learning how to repeat the tasks we challenge it to produce. So the more often you practice muscle irradiation, the better your body will become at creating stability, generating force and promoting inter-muscular coordination so your body performs as a single unit.

Think of your muscles as the orchestra and the CNS as the conductor, the more often these two “recite,” the more harmonious the music of your lifting will be.

This is why you would typically perform a really heavy squat with both feet on solid ground instead of standing on a bosu ball. (Please don’t do it for the ‘gram. )

You can only effectively express strength from a position of stability. So it makes sense that if creating tension translates to increased stability, it would be extremely beneficial to include this technique in your training.

The cool thing is that all this force production requires an increased amount of energy which translates to more calories burned for the same time investment. Can you say increased fat burning?! (Sign me up!)

Too Much of a Good Thing?

There are some cases where you may not want to lift with maximal tension. When you are performing a high number of reps (more than 12) using a given weight, chances are the load will be pretty light and there would be much less of a need for the use of this method. You are better off performing your repetitions with a steady tempo and a moderate amount of tension vs. the I-am-The-Rock-and-I-will-break-this-kettlebell level of tension you use for heavy lifts.

For example, while you’d want to remain tight during a ballistic move like a kettlebell swing, your arms have to remain relaxed and you typically “relax” at the top end range of the swing. Trying to actively squeeze all your lower body muscles and arms the entire time would make the movement less efficient.

Key Takeaway

This technique is best reserved for heavy compound movements involving multiple muscles. Vary the amount of tension depending on the exercise.

Bringing It Home

The next time you’re lifting, try this out and think about inviting all your muscles to the party instead of just whatever area you are targeting in a given exercise.

You’ll probably be able to go a little heavier or perform extra reps.

This will help you burn more fat by way of the increased energy demand on your body and also keep you safe by creating a position of stability.

Because, science. 

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Wanna work out with a bunch of fitness nerds who make concepts like muscle irradiation seem less geeky than they actually are? Schedule a Health & Hotness Strategy Session at Mark Fisher Fitness.

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New York native Miguel Alemar is a certified strength coach and sports nutritionist. He has interned and worked with some of the top minds of the fitness industry over the last decade. He loves helping people discover their strength and how to fuel their activities. A self-described science geek, he uses an evidence-based approach to both his training and nutrition practice. He has a ton of letters after his name to impress you but the real impression comes from the consistent results he delivers. When not writing about himself in the third person, he enjoys time with his family and friends, being a foodie and picking things up and putting them down. (Duh!) You can connect with him on Instagram, Twitter or online at Hardknox Training.