What Are Stabilizer Muscles (and Do They Really Need to Be Trained)?
You may have heard that dumbbell exercises are better than barbell exercises because they engage more stabilizer muscles, or that free weights are better than machines for the same reason. But what are stabilizer muscles? And do you really need specific exercises to train them? It turns out there are a lot of misconceptions surrounding this term, so let me clear things up.
What are stabilizer muscles?
This is where confusion arises, as there is no consensus on what stabilizer muscles actually are . A 2014 study searched the literature for references to stabilizer muscles and attempted to provide a definition. They concluded: “muscles that contribute to joint stiffness through co-contraction and exhibit early activation in response to perturbation via a feedforward or feedback mechanism.”
So, stabilizer muscles are muscles that actually stabilize. Which muscles exactly are they? That’s a more complex question. A muscle may stabilize a joint during one type of exercise or movement, but that doesn’t mean it always acts as a stabilizer. Just as an actor might play a supporting role in one film and a leading role in another, muscles aren’t necessarily limited to a “stabilizing” role. Thus, stabilizers aren’t a type of muscle, but rather a role a muscle may or may not play in a given context.
Returning to the scientific literature, you can find numerous studies on “lumbar [lower] stabilizers,” “trunk [core] stabilizers,” or “knee stabilizers.” But it turns out that these are not just muscles that stabilize joints. This study on knee stabilizers mentions four muscles that make up the quadriceps and hamstrings (the large muscle groups on the front and back of the thigh, respectively). Are these stabilizers or simply muscles that move the legs?
In one exercise, the stabilizer muscles may be the primary muscles in another.
That’s why I’m not overly concerned about a particular training program (such as one using weight machines ) ignoring the “stabilizer” muscles. If you perform a variety of exercises for your quadriceps and hamstrings, you’re practically guaranteed to engage these muscles, which act as stabilizers for the knee during running and jumping.
For example, single-leg exercises like step-ups and lunges are great for working the abductors (hip muscles) and adductors (inner thigh muscles), as these muscles provide stability to the leg when bearing weight. Even if you’ve never done single-leg exercises before, you can still work these muscles by performing exercises that target their primary motor groups, such as using adductor and abductor machines.
Stability is not only strength, but also coordination of movements.
If we look again at the research on the knee stabilizer muscles, we see a theory that using these muscles during running and jumping helps prevent injuries. It’s not just the strength of these muscles that matters, but also your ability to activate them when needed.
Thus, knee stability is ensured not only by free weight exercises—although they are also very useful—but also by running, jumping, turning, and making sudden changes in direction. (Think of football players running around cones and rope ladders.)
In other words, joint stability requires not only strength but also practice . If you want to maintain stability and steadiness while performing certain movements, you need to train your brain to engage these muscles at the right time and in the right sequence.
Strength and stability are sometimes at odds with each other.
So, what should you do in the gym? You’ll notice that strong people typically train using a combination of different exercises. They might squat and bench press, but finish their workout with dumbbell bench presses or leg extensions. Training is a continuum, with strength at one end and stability at the other, and each exercise falls on a different level of that continuum.
Let’s take the bench press as an example. When performing a barbell bench press, you use your legs to stabilize your torso, your torso to create a stable base for your arms, and your arms to move the weight. While you’re training your pectorals and triceps as the primary movers, you’re also engaging numerous muscles in your shoulders, core, back, and legs as stabilizers.
We can engage our stabilizer muscles more actively if we perform, for example, dumbbell bench presses on a fitness ball. We’ll have to work harder to maintain stability, but as a result, we won’t be able to use as much weight. We’ll be training our stabilizers more, but our primary muscles (chest and triceps) less.
At the opposite end of the spectrum is the bench press machine. There, you barely need to stabilize your muscles—all you need to do is sit on a chair without falling over. The pectorals and triceps are no longer limited by the capabilities of our stabilizers, so we can “lift” even more weight. (Of course, it’s important to remember that the names of these machines aren’t comparable to barbells or dumbbells ; their mechanics are different.)
So, is it necessary to “train” the stabilizer muscles?
My opinion is this: if you train every body part, regardless of the training method, you’ll ultimately train all your stabilizer muscles. Yes, even if you only do machine exercises. The key is to have a balanced program.
If you’ve only been doing “functional” exercises that require significant stabilization, you’re likely overtaxing your stabilizer muscles without even realizing it. As a result, you may not be paying enough attention to the core muscles involved in each exercise.
You can easily get the best of both worlds by varying your exercises. If you never do anything that makes you feel unstable, add single-leg exercises, weighted carries, or other exercises with a little instability to your routine. ( Standing on a Bosu isn’t necessary, although you can if you want.) And if you’re working hard on stability, try machine or barbell exercises from time to time to ensure you’re also developing strength.