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The Stability Continuum

‘Sup readers? I know all three of you have been wondering where I’ve been since my last post (Haha. That was funny). Well, let me update you.

  1. I’ve left my job as a personal trainer at Fitness Together in Bridgewater and transferred to MBX Training in Norwell, Massachusetts as a Sports Performance Coach. The facility is and the staff is equally awesome.
  2. I attended a USA Weightlifting Sport Performance Certification course and finally got certified to teach Olympic progressions. I had been learning on my own for a while, but it was good to reaffirm what I had already learned.
  3. I officially became a Certified Strength and Conditioning Specialist (NSCA-CSCS).

Me and Lauren after Myrtle Beach.

I also went to Myrtle Beach with Lauren. It was the week before Memorial Day weekend, also known as Black Bike Week (a.k.a. Atlantic Beach Bikefest). Look it up.

We stayed in a villa a short walk from the water and were able to spend each morning at the gym (it even had a squat rack!), each afternoon on the beach and by the pool, and every night at bars and restaurants. I got sunburned the first day on the top of my feet and my skin is still peeling. The villa was perfect because we were able to save some money by cooking breakfast and lunch every day.

If you’re familiar with Myrtle Beach, you probably know about Barefoot Landing and Broadway at the Beach. They’re shopping/entertainment centers that are built around lakes. Broadway has a mini-Codzilla that whips around the lake and that’s pretty cool. Also, if you’re looking for a solid meal at Barefoot Landing, Bully’s is a bar/pub style restaurant with an outside patio where we had some solid burgers on Wednesday night.

So if you’re still paying attention, I want to give a little introduction to the word “stability.” Stability is an integral part of athletic performance, but perhaps more importantly, longevity and health.

Of course, you can’t maintain a single-leg stance (a frequent occurrence in athletics) without stability. But you also can’t keep your shoulders healthy if instability prevents you from maintaining glenohumeral joint centration. Here are my personal definitions of mobility, stability, and strength.

  • Mobility – the ability of a joint to move throughout it’s full range of motion without any soft tissue or capsular restrictions.
  • Stability – the ability to actively resist extraneous movement of the skeletal system; usually referring to joints or the core.
  • Strength – the maximal amount of a force that a muscle can produce.

I’ll also distinguish between strength and power. Power is “fast strength,” the ability to produce force quickly. Powerlifting can actually be a bit of a misnomer because the speed at which the lifts are performed can actually demand less power than an Olympic lift.

So, back to stability. The red-headed stepbrother of flexibility (a traditional name for mobility, though I believe better mobility considers all aspects of the joint, not just the muscle) and strength. Without stability, mobility is worthless. And without stability, your ability to develop true, “real-world” strength will forever be limited.

So let’s take a look at traditional exercise through a stability-lense and objectively determine which mode of resistance training will lead to the greatest improvements in mobility, strength, and stability.


There are a ton of different machines out there, so let’s just take a quick look at the most popular kinds. For starters, why do people use machines? They offer a few benefits over free weights:

  • Easy to learn – you don’t need a trainer or a coach to teach you how to utilize a machine.
  • Easily isolate muscle groups.
  • Generalizable – along with being easy to learn, machines allow all types of people to perform exercises when the may not be able to use their bodyweight (due to strength or weight imbalances).

Walk into any gym, and you’ll probably find some sort of stack-loaded where you set the pin and perform the exercise. The other type of machine is plate-loaded, where there is a place on the actual machine to load weights and change the resistance manually.

Machines often become a stack-size competition.

Both are typically body-part specific and involve isolating certain muscles or muscle groups. Along with isolating muscle groups, machine exercises typically allow people to use more weight than can be used during a free weight exercise, because there is no stability required during a machine movement. The restricted range-of-motion limits your mobility and therefore the stability required.

For instance, in performing a leg extension, the rectus femoris bears most of the load with help from the vastus intermedius, lateralis, and medialis. However, the medialis and lateralis are not required to stabilize the patella over the knee joint (a necessity in free weight movements). Therefore, leg extension strength does not correlate to squat or single-leg strength if one is using exclusively machines. Furthermore, movements that demand knee extension typically also require the incorporation of the glutes, hip rotators, hams, and adductors, muscles that aren’t activated in coordination with the quadriceps during a leg extension.

In short, machine training builds non-functional strength in isolated muscle groups without much activation of stabilizers. While possibly useful in specific rehabilitation scenarios or bodybuilding workouts, exclusively using machine training is limited in its carryover to real life movements.

The quintessential stupid unstable surface exercise.

Unstable Surface Training

On the other end of the spectrum is unstable surface training. Unlike machines, where the body is confined to a certain range-of-motion, unstable surface training does not promote a certain ROM and the body is required to provide the stability in order to perform the exercise.

One would assume that increased stabilizer muscle activation would create a more functional exercise overall and a better experience for the exerciser. But a quick Google search will provide you with a wealth of evidence saying exactly the opposite.

In fact, an increase in stabilizer activation also comes with a decrease in prime mover activation. Going back to our quadriceps example. If one was to squat, let’s say, on a Bosu ball, you would assume that the inherent instability would cause greater activation of muscles such as vastus lateralis & medialis, glute medius, hip rotators, and various hamstrings. Meanwhile, prime movers such as rectus femoris activated less.

Furthermore, exercises like Bosu ball pistol squats require an inherent baseline amount of strength in the hip stabilizers (gluteals, hip rotators) to perform the exercise. Someone without this hip stability probably won’t be able to safely or effectively perform the exercise.

This is why you can’t lift as much weight. The body’s energy is being used to stabilize the movement rather than actually lift any substantial weight. I like to think of my body as a bucket of rocks and sand (that sounds funny to say). If you fill the bucket with too much sand, there isn’t any room for the rocks. And by the same token, too many rocks won’t leave room for any sand. If you try to make a sandcastle out of rocks (as with our machine example), it will fall over. It needs sand.

Again, to summarize this section, while increased stabilizer activation might be good in isolated scenarios, the strength aspect is missing. Your ability to use heavier weights will be limited, which can be a good thing in many instances. However, if you never lift heavy weights on solid ground, you’ll never get better at lifting heavy weights on solid ground.

The Middle

So what are we left with? We’re left with bi- and unilateral movements to be performed on solid ground. This includes bilateral leg movements like squats and deadlifts. Unilateral movements like reverse lunges or SL RDL. Bilateral upper body pushes like pushups. And core exercises like planks.

Now, I know what you’re thinking. What if these exercises are too easy for me? I’m too advanced to do regular ol’ squats. And you know what my answer is going to be. Do. Heavier Squats. Are your pushups not hard enough? Maybe try a different upper body push like a dumbbell military press and use your pushups for prehab or bodyweight challenges. If you can dumbbell military press half of your bodyweight, I’d call you a strong person. As for core exercises, progress your planks to rollout variations. And if you don’t think your single-leg exercises are hard enough, think again. And watch this video. (As a side note, thank god somebody finally found a good use for an aerobic step.)


So if we take a quick look at what we’ve just discussed, we can determine that a solid training plan should include a few factors:

  • The majority of our training should come from barbell and dumbbell training.
  • Some training can come from cable machines, preferably two-handed.
  • Unstable lower body training should be preceded by advanced single-leg lower body exercises (if you aren’t sure whether you’ve advanced enough to perform a single-leg-Bosu-ball-jump-squat-deadlift-push-press-thing, feel free to ask my opinion).
  • Unstable upper body training can be accomplished with bottoms-up kettlebell work.
  • Machines should only be used to activate very specific muscle groups in specific scenarios (e.g. rehabilitation).
  • Unstable surface training (e.g. single-leg, bottoms-up KB) can be an effective way to get a training effect while sparing your joints.

I didn’t cite any sources for this post because, like I’ve said before, you can pretty much prove anything you want in a controlled environment. “The study has proven that there is significant EMG activation of the quadriceps during the Bosu ball squat exercise … as compared to lying down.” See what I did there? In reality, here’s the continuum of stability, from least to most stable:

Bosu ball/bottoms-up KB — Single-leg/single-arm dumbbell — bilateral dumbbell/barbell — machines

I’m not anti-unstable surface training, but I believe that single-leg and single-arm dumbbell work are certainly enough to begin with. And I think most people would find that a correctly performed goblet squat or pushup provides plenty of activation of the intrinsic stabilizer muscles of the body. We don’t perform our sports or daily activities on unstable surfaces, so why should we spend the majority of our training on an unstable surface?

With all that being said, this article is done. Now go be awesome and lift some damn weights.

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