Buzz
You might have heard that dumbbell exercises are superior to barbell ones because they engage more of your "stabilizers," or that free weights offer an advantage over machines for the same reason. But what exactly are stabilizer muscles? Are they really underworked during machine exercises, and is it crucial to focus on them in your training?
What are stabilizer muscles?
This can be a bit unclear, as there’s no universal agreement on the definition of stabilizer muscles. A 2014 study combed through the literature to find references to stabilizer muscles and attempted to provide a definition. Here’s what they concluded:
Muscles that help stabilize joints by co-contracting and show an early response to disturbances, either through a feed-forward or feedback control system.
So, stabilizer muscles are muscles that provide stability. But which ones exactly? That’s a tricky question. There's abundant research on "lumbar [lower back] stabilizers," "trunk [core] stabilizers," or "knee stabilizers." However, these aren’t specific muscles that exclusively stabilize joints. For instance, a study on knee stabilizers identifies four muscles from the quadriceps and hamstring groups (the large muscle groups at the front and back of the thigh). Are these stabilizers, or are they just muscles that move the legs?
The stabilizers in one exercise might serve as the main movers in another.
This is why I don’t stress too much about machines missing out on "stabilizing" muscles. If you perform a variety of quad and hamstring exercises, you're almost guaranteed to target the muscles in the quadriceps and hamstrings that act as knee stabilizers when you run and jump.
Alternatively, single-leg exercises like step-ups and lunges are excellent for activating your abductors (hip muscles) and adductors (inner thigh muscles) because these muscles help maintain leg stability when bearing weight. However, if someone never performs single-leg exercises, they can still work these muscles by doing exercises that focus on them as the primary movers, like abductor and adductor machines.
Stability is more about coordination than sheer strength.
Revisiting the research on knee stabilizers, scientists suggest that it's beneficial to engage those stabilizer muscles while running and jumping. It's not just about the strength of these muscles but also your ability to activate them when needed.
Maintaining knee stability isn’t only about free weight exercises—though they’re excellent—but also involves activities like running, jumping, pivoting, and cutting. (Think of soccer players navigating cones and rope ladders.)
In essence, practice plays a crucial role in joint stability, not merely strength. To remain steady and stable during specific movements, you must train your brain to activate those muscles at the right moment and in the proper sequence.
Strength and stability don’t always align perfectly.
What should you focus on at the gym? Strong individuals often blend various exercises into their routines. They might start with barbell squats and bench presses, but wrap up with a dumbbell bench press or leg extensions. Fitness lies on a spectrum, with strength on one side and stability on the other, and every exercise falls somewhere in between.
Take the bench press as an example. During a barbell bench press, your legs stabilize your torso, your torso serves as a solid base for your arms, and your arms do the work of moving the weight. While your pecs and triceps are the main muscles in action, your shoulders, core, back, and legs also play a key role as stabilizers.
We can increase the activation of stabilizers by performing a dumbbell bench press on a yoga ball. In this case, you'd need to work harder to maintain stability, but you wouldn’t be able to lift as much weight. The stabilizers get more attention, while the main movers take a step back.
With a chest press machine, the opposite occurs. Stabilization is minimal—just enough to stay seated properly. The pecs and triceps aren't held back by stabilizers, allowing you to lift more weight. (However, remember that machine weights don’t directly correlate to barbell or dumbbell weights; their mechanics are different.)
So, should you actively “train” your stabilizers?
Here’s my take: If you train every muscle group, no matter how you approach it, you will engage all your stabilizer muscles. Even if you follow an entirely machine-based routine. The key is that the routine should be comprehensive.
If you've been sticking to “functional” exercises that require a lot of stabilization, you're likely working your stabilizers more than you think. However, the downside is that the primary muscles may not be getting as much work as they should.
You can easily strike a balance by diversifying your exercises. If you don't regularly perform movements that challenge your balance, try adding single-leg exercises, carries, or other slightly unstable exercises to your routine. (You don't have to stand on a bosu, unless you want to, of course.) And if you're focused on stability training, throw in some machines or barbell exercises from time to time to ensure you're building strength too.
