Stand up and make a fist as hard as you possibly can. Go ahead, squeeze!
Okay, what did you feel?
If you truly squeezed your hardest, you probably felt all of the muscles of your arm engage, not just your forearm. Yet all I instructed you to do was make a fist, so why’d that happen? Is it magic?
Nope, it’s science.
Specifically, it’s called the principle of irradiation, which Dr. Roger Enoka defines as a spread of muscle activation that “augments postural stability and enables the transfer of power across joints by two-joint muscles.”1
In simpler terms, making a fist sends a signal to all of the surrounding muscles to activate.
Thus, simply by flexing your fingers into a death grip, your biceps, triceps, pecs, lats, and even the tiny muscles of your rotator cuff are all cued to engage in tandem.
Our bodies know this principle instinctively, of course. When challenged to a fight, we generally don’t straighten out our fingers in order to deliver our best slap.
Instead, we ball up our fists and position them in front of our faces to repel or deliver a punch. It’s from this position that we’re globally at our strongest.
Make a Fist when Strength Training
As you may have guessed from the title of this article, irradiation has tremendous implications for strength and performance. Essentially, strength can only be expressed in the presence of full-body tension, which is exactly what irradiation affords us. Not only that, it also intensifies the contraction of the target muscle.
Take even a simple exercise like a bicep curl. At a minimum, you have to squeeze the bar just so it doesn’t slip out of your fingers. But from a broader standpoint, power must be transferred throughout the body to avoid energy leakage.
The wrists must be locked into a stacked position, and the shoulders need to remain down and back. Even the hips have to stay strong and immobile, lest the curl turn into an ugly hang clean. Making firsts around the bar irradiates the muscular contraction to all of those neighboring joints in order to accomplish the aforementioned tasks.
In addition to the contractile benefits of irradiation discussed above, making a fist also serves a more primal function, aggression. Of course, in light of the previous example of a fighting stance, this make sense. But how does aggression play into lifting weights?
Consider a maximal effort bench press. There’s little room for fear when tasked with preventing more weight from crushing your chest cavity than ever before.
In this case, squeezing your fingers around the bar replaces that fear with aggression. Furthermore, from a muscle activation standpoint, irradiation sends a signal to the rotator cuff to “pack” itself, which provides a more stable base at the shoulder to press up from.
Clearly, the same strategy can be applied to any bilateral lift (deadlift, squat, overhead press, etc.). It can even be applied to bodyweight exercises like pull-ups, glute bridges, and – perhaps the most well-known example of irradiation of all – the RKC plank.
In the RKC plank, popularized by Pavel Tsatsouline, the fists irradiate a full-body contraction up through the lats and down through the anterior core, glutes, quads, and even the muscles of the lower legs. This style of planking is so intense that sets can last no longer than 10 or 15 seconds.
Application to Unilateral Movements
The principle of irradiation can be applied to other exercises, too, like unilateral ones. Although unilateral exercises are sometimes just an afterthought in many strength training programs, they’re actually some of the best applications of irradiation.
You see, failure to complete a heavy one-sided lift is often due not to a strength deficiency on the working side, but rather an issue with tension generation on the opposite (non-working) side.
Take a one-arm dumbbell bench press, for example. What do most people normally do with their non-working arm? Perhaps they drape it across their chest to feel their pec working, or maybe they put it on their hip to use as a counterbalance.
It turns out that the best strategy is actually to extend that arm all the way out to the side and make the hardest fist possible. That contraction will irradiate up the arm and across the core, thereby preventing rotation of the torso and stabilizing the entire body to ensure a successful press.
The same principle can be applied to a number of other exercises that are loaded on only one side: one-arm overhead presses, one-arm one-leg Romanian deadlifts, and off-set kettlebell front squats to name a few.
As a tactile cue to reinforce squeezing, you can also attempt to crush an object like a shaker bottle or stress ball in the non-lifting hand.
When Not to Irradiate
Despite the myriad benefits that irradiation does provide, there are a few instances in which making a fist would be ill-advised.
When weights are light and the training goal is geared more towards endurance, squeezing the fists becomes a poor use of energetic resources. In these cases, you want to relax the hands and generate just enough tension to accomplish the task.
A good example would be sets of high-rep kettlebell snatches. You should keep the non-working hand relaxed and strategically loosen the fingers of the working hand around the handle of the bell to provide brief periods of rest during the recovery between reps.
Similarly, in the case of a longer duration front plank, it’s best simply to place the hands flat on the floor to avoid creating too much unnecessary tension and also to provide more feedback for the position of the body in space.
Finally, when using “reaching” as a teaching tool for an exercise (i.e. hands-free “Frankenstein” front squat), it’s better to extend the fingers in the direction of the reach to promote the lengthening action than ball them up in a fist.
1. Enoka R. Neuromechanics of Human Movement. 5th ed. Champaign, IL: Human Kinetics; 2015.