By Chris Finn
The concept of unstable surface training blew my mind back in the late 2000s. To help pay tuition while I was finishing up physio school, I was training at a big box gym. At that time, it seemed to make so much sense as a way to improve an athlete’s balance and, ultimately, their performance. If they can do it on an unstable surface (which is harder, right?), then I would surely be setting athletes up for huge results.
I was young and excited, and I threw everyone who would let me train them and their mother onto a Bosu ball, balance disc, or physioball. The more complex and unbalanced the activity was, the better. The clientele loved it! If you were training during this period, I am sure you had someone at some point on a balance disc, an Airex pad, or some other sort of unstable surface. Everyone was doing it!
Need to get “toned” for your wedding? Bicep curls while standing on one leg on a Bosu ball is the answer—while your arms are toning, so are your legs. It’s functional!
Want to play golf in college? Working on rotational drills while standing on a Bosu ball or half foam roll is the key. If you can swing and stay balanced on the unstable surface, then you’re going to crush the ball on the course because the ground doesn’t move!
Want to play basketball in college? We definitely need to do all of your work on a physioball and Bosu ball, so you have to use your glutes and entire body to stabilize while you get strong. No way you sprain your ankle now!
I was a genius…and everyone in the gym was blown away by my creativity. They loved that it was new and different. I had a long waitlist of clients to train with me because of a serious case of FOMO.
Unfortunately, my professors in physical therapy school didn’t help curb my “genius.” Evidence-based practice was all anyone talked about, and they were focused on all the great rehabilitation literature that came out at this time.
There were studies that showed proprioceptive training allowed athletes to improve static and dynamic postural control. It not only could have important applications for preventing injuries such as ankle sprains and knee injuries, but might also improve sports conditioning parameters.1 When you read a bit deeper, however, those “sports conditioning parameters” likely didn’t really mean anything for your athlete’s sport. Back then, though, I missed that important part.
This research was very exciting, as it seemingly gave us a way to improve an athlete’s ability to recover balance after an injury. The research also seemed to suggest that there was a possibility of preventing injury by incorporating proprioceptive training into an athlete’s regimen. Remember this research for later in the article as I’ll come back to it.
As if this wasn’t enough, all the EMG studies furthered our obsession with how great unstable surface training was. I can’t remember a single class in physical therapy school where an EMG study wasn’t brought up in support of a reason to do a specific exercise because it “increased muscle activation.”
EMG – More Activation Doesn’t Always Mean Better Outcomes
There are numerous studies out there that highlight the increase in muscle activation levels when you train someone on an unstable surface. These studies particularly highlight the deep core and the other “stabilizing” muscles. They point out which specific exercises on unstable surfaces elicit the highest activation levels in specific muscles.
This research was great for those of us looking to hit specific muscles or areas to train up performance and do it via unstable surface training. The research seemed to support that we were doing the right things and that unstable surface training was a viable option. Unfortunately, as I came to realize later in my career, I was just looking at research and data long enough and in enough different ways to tell me what I wanted to hear. I was not critically and objectively reading the research: unfortunately, I was cherry-picking it.The research seemed to support that we were doing the right things and unstable surface training was a viable option. Unfortunately, I was cherry-picking the data. Click To Tweet
Want to target the obliques more than the rectus abdominis because your athlete has a serious deficit there? Have your athlete do a crunch on a physioball instead of a traditional crunch, as the research shows increased oblique activity with this variation (and decreased rectus activation). I’m not sure how or why you would assess this objectively for sport performance, but the research says you can train those obliques up if you want to!
Fast forward a decade. Today, I have quite a different lens through which I attempt to evaluate all this.
As someone who works exclusively with rotational power athletes and has taken a deep dive into the research, I know this is where the caution flare needs to be shot up for all coaches and physios when it comes to EMG studies and the subsequent unstable surface training that has been touted for over a decade. The gluteus medius is probably the most famous EMG target and my personal favorite. If you are a coach or physio, you have definitely said or heard the phrase “we have to get your glutes firing.”
It made its way through the physio ranks and into the mass media spotlight when Tiger Woods told the world his “glutes weren’t firing” after a round of golf in the mid 2010s. After Tiger said he needed his glutes firing, I am sure the sale of minibands skyrocketed for those abduction walks!
If we stop to think about this for a second, however, obviously his glutes were not paralyzed…they were doing something, right? If they weren’t, how would he have been able to walk and how was he swinging the golf club over 120 mph? This is where my head went, and I hope yours does as well.
This Misunderstanding of EMG Research and Unstable Surface Training
Through all of my research digging, I was unable to discover where the idea of needing to train the deep core and stabilizing muscles even came from. My best guess is that it’s from the rehab world, though. I did find that researchers in one study were unable to find any diagnosis or articles reporting selective deficits of core muscles in strength-trained athletes. They went on in their article to discuss how confused they are about what data even led to the demand for specific exercises to strengthen the deeper trunk muscles, in particular, or improve the ability to selectively activate them. Furthermore, they were unable to find any evidence that classical strength-training exercises (e.g., squat, deadlift, snatch, and clean and jerk) affect only “global” muscles or lead to imbalances between the muscles of the trunk.2
This was of particular interest to me as I dove deeper down this unstable surface training rabbit hole. Wasn’t that the whole reason we had people doing unstable surface training in the first place? We wanted to target those deep stabilizers that did not get hit as well in traditional strength training, right? This only further confused me as to why we all started training this way in the first place. Perhaps it was nothing more than our innate desire for something new and exciting? I kept digging.
Electromyography has traditionally been used to measure changes in externally measurable force. Muscles used to aid in joint stability can contribute significantly to electromyographic signals without altering measurable force.3This means, simply, that you can increase how much muscular activity an EMG will read in a specific muscle group by having an athlete do something in a different way, but without it necessarily being in a way that positively impacts sport performance. For example, that’s great that your gluteus medius fired 20% more on the balance disc, but did you hit the ball farther or straighter afterwards?While you’ll naturally see increases in the stabilizing musculature activity when someone is on unstable surfaces—does it translate to performance? Click To Tweet
If I have an athlete swing a golf club on a Bosu ball, they have to try not to fall down. To achieve this, there will often be increased activation of their glute med and other hip stabilizers. While there will likely be an increase in EMG activity in these areas, the question that I wanted to know was if they would swing any better? While you will naturally see increases in the stabilizing musculature activity when someone is on unstable surfaces, particularly in the ankles and hips, the only question that matters is “Does it translate to performance?”
Somewhere along the line, people decided to circumnavigate the final connection to performance and instead moved past GO, collected their $200, and jumped to the conclusion that unstable training improves performance because it increases muscle activity. Hence, we arrived at “If you train golfers to swing on unstable surfaces, they will be better for it.” Born at this point was Golf Digest’s Dustin Johnson swinging a golf club while standing on a physioball—classic.
The belief was that having a golfer’s “stability muscles” firing at a higher rate would transfer to better performance because they would be more stable. If we accept this level of clinical reasoning, we should be putting all of our golfers and athletes on unstable surfaces because it increases neural drive to the stability centers, which is the key factor for performance.
The problem with this line of thinking, unfortunately, is that it fails to read the next line in much of the research that addresses the impact on performance of all this increased activity in the stability centers. Above and beyond what would be necessary on the stable ground where the game of golf and many other sports are played, the benefits of unstable surface training dissipate. The increased training of these stability centers has a point of diminishing returns and has even been shown to decrease an athlete’s ability to produce power.4
The flare of caution on EMG studies is one of paralysis by analysis. I believe the lack of applicability to performance actually gets lost in all of the numbers and confusing scientific terms of analysis. All of this EMG information is nice to know, but its applicability and usefulness in the training of high-level athletes is questionable at best. Coaches training high school, collegiate, and professional athletes would be better off if they forgot EMG studies exist on unstable surface training.Coaches training high school, collegiate, and professional athletes would be better off if they forgot EMG studies exist on unstable surface training. Click To Tweet
At the end of this deep dive into the research surrounding unstable surface training, EMG studies appeared to make up a large percentage of the studies that people would use as rationale to train specific muscles and areas. The EMG argument for unstable surface training loses its steam when you view it in the context of sport and performance. Performance happens in uncontrolled environments on stable ground and requires large amounts of power output in most sports. In most cases, EMG studies on unstable surfaces occurred in controlled environments on unstable surfaces with diminished power outputs.
Rehab vs. Sports Performance Applications
This is where the real discussion of this article begins, and we need to start by drawing a vivid line in the sand.
Unstable surface training has been shown to be useful in rehab settings to improve proprioceptive skills and capabilities. That’s it. There are clear positive medium- and long-term effects to proprioceptive measures reported in studies when the athlete is not acutely fatigued from proprioceptive training.1Unstable surface training has been shown to be useful in rehab settings to improve proprioceptive skills and capabilities. That’s it. Click To Tweet
Unstable surface training has not shown value in sport performance training for rotational power athletes or any other power athlete and actually has been shown to be detrimental.
That’s the line for where unstable surface training is applicable and helpful. Hopefully, that’s clear enough. Let’s go deeper into the discussion about unstable surface training in the weight room.
Unstable surface training actually should be used with caution in the weight room because it produces short-term negative performance outcomes due to proprioceptive fatigue.1This means that if a coach preceded heavy power work with intense proprioceptive training, they could actually increase the chances of injury to the athlete because their proprioception would be acutely worse. Coaches and physios should, however, make sure to stress an initial warm-up on stable ground such as a traditional dynamic warm-up, as this showed a general improvement trend in the control group of this study1.
Leave the Airex pads and balance discs in the closet and avoid unstable surface training as part of your warm-up with your athletes. Keep the dynamic warm-up on stable surfaces and you will set up your athletes to perform better in their workout.
In another study, unstable surface training was found to lower maximum strength and muscle activity in deadlifts. In this particular study, it did not increase performance, nor did it provide greater activation of the paraspinal muscles.5The deadlift is one of the most important lifts for golfers to develop strength in, and if you extrapolate these findings to other lifts, it makes you question further the value of unstable surface training to performance in other exercises.
To further this deadlift finding, another study looking at unstable versus stable surface training found that there is a mean force deficit of 29% with unstable surface training compared to similar stable training surface exercises.6This is HUGE! For those of you training higher level athletes, putting them on unstable surfaces trains your athletes to produce less force. Not an ideal scenario.For those of you training higher level athletes, putting them on unstable surfaces trains your athletes to produce less force. Not an ideal scenario. Click To Tweet
To be objective, a number of studies have found equivalent output or no difference in strength outcomes with unstable versus stable training with strength and power markers. To be fair to the faction of physios and coaches who use unstable surface training regularly, it does work, and this is for you! But—and this is a big but—these studies were only done on relatively untrained or older adults, not high-level athletes. Remember, higher level athletes saw decreases in performance when using unstable surfaces, likely due to the, on average, 30% less force created.
This research, in my opinion, is not applicable to the sport performance world, but rather the general fitness and rehab worlds. If you work with seniors or other untrained individuals where you would not recommend higher level loads anyway, there appears to be an equal benefit to unstable and stable surface training on strength gains and power gains. I would call this the “newbie gain” phenomenon. No matter what you give them, they will get better.
There is a threshold, however, where the law of diminishing returns sets in for unstable surface training and it actually starts to become a detriment as shown in the research. It is up to us as professionals to identify where that threshold is and implement appropriate progressions. If you regularly test and retest your athletes, identifying these sorts of negative changes should be simple.
I see this threshold being crossed a lot with our adult golfers who come out of rehab from other locations. Many physio clinics do not progress their patients beyond unstable surface training and low-level TheraBand training. This leads to many recreational athletes and golfers still using low-level training and unstable surface training months and even years later. Because they are not progressed beyond the initial newbie threshold, many of them have significant strength deficits relative to the demands of golf or other sports they enjoy. This, unfortunately, leads to them facing subsequent repeated overuse injuries due to low resilience.
I am guessing, however, that most people reading this are not looking to train “average.” You are looking to train elite athletes who will perform at extremely high levels and require significant stimulus to see training improvements. If this is the case, unstable surfaces are not your answer…emphatically. In fact, they are your anti-gain, as demonstrated by decreased power outputs in elite level players when training on unstable surfaces.4If you train elite athletes who will perform at extremely high levels and require significant stimulus to see training improvements, unstable surfaces are emphatically not the answer. Click To Tweet
Despite the research, golf fitness professionals and golf teaching professionals hold deeply to their personal need to work on “stability” in their golfers. And no one will argue that stability in the golf swing is important. The challenge is that the solution in golf workouts is often to use unstable surface training. Because of this, I wanted to dedicate an entire section of this article to this topic.
Training Stability and Balance in Golf
If you have been in or around the game of golf, you have undoubtedly heard people talk about the importance of stability and balance in the golf swing. These aren’t novel concepts or unique to the sport of golf.
What you have not likely heard is a unified consensus on how to best train those traits. You also have not heard how to objectively measure and define what balance and stability is in the golf swing. This is where the problem starts.
On the instructional side, many golf instructors have taken to having students hold different positions in their swing on half foam rollers, balance discs, or other unstable surfaces. This makes sense to them, as they operate under the same logical line of thinking that I did when I started training back in the late 2000s. If they can get the athletes to be “stable” at the top of their swing or impact and “feel the position,” it surely will be easier for them when they are swinging full speed on stable ground. As we saw earlier, this line of thinking is severely flawed.
There is often a huge emphasis on “turning golfers’ glutes on” in the golf swing and activating all sorts of scapular muscles, etc. It is not uncommon to hear a golf instructor tell a golfer to turn their glute med on in the back swing and/or really fire their serratus anterior on the trail side during the downswing. Oh, and simultaneously fire the infraspinatus and teres minor on the lead arm through impact to make sure you finish your release. I am not sure how this all became so ingrained in the line of thinking in golf performance. I suspect it came from the rehab world, where we physios are famous for having athletes do clamshells until their glute medius doesn’t function anymore and then telling people to “squeeze their glutes” when they walk.
At any length, we all know that internal cues are the absolute worst thing to give an athlete to think about when it comes to performance. The best instructors in the world totally understand cueing and everything that goes with it, but they are the minority, unfortunately.
Playing basketball in college, I can’t imagine my coach telling me to fire my glutes when I took a jump shot or jumped for a rebound. That’d be crazy. Yet, that is what many golfers get during their instructional lessons every day across the country.Again, if it looks like a golf swing, it has to be good for the golfer—until you dive into the research. Click To Tweet
In the golf fitness world, much from the influence of this line of thought, the idea of training balance and stability just morphed into putting a weight in someone’s hand or giving them a cable to rotate with. Again, if it looks like the golf swing, it has to be good for the golfer—until you dive into the research.
We see all sorts of examples of this on social media, in major golf publications, on the Golf Channel, and even in the warm-ups and workouts of the best players in the world. In most cases, I have noticed one of two extremes when it comes to “golf fitness” training.
On the one side of the spectrum is what I call the “Mystical Physio.” This approach is where athletes are trained with little more than a band in all sorts of fancy PNF and other neuromuscular approaches. The golfer (and coach) are afraid of the golfer getting hurt and so don’t use heavy weights. The claim is that they are training neuromuscular firing patterns to maximize efficiency and stay flexible. Ironically, this leads to golfers having poor resilience to the rigors of Tour travel and demands, and increases the likelihood they will be hurt. On a sad note, I have seen this approach be the death of many careers for hypermobile golfers whose only hope for longevity was getting stronger.
The other side of the spectrum is what I call the “Tortured Trainer.” We all know one. They can’t go a week without making up a new exercise and posting it all over social media to show how creative they are. There are always lots of comments about how awesome the exercise looks and how people can’t wait to try it out. The buzz builds, especially when it is a top Tour pro doing it, and next thing you know, all the golfers in the world are incorporating it into their workout.
A recent example I saw of this could only be described as a rear foot elevated jump and land in place with the rear foot elevated stance maintained, followed immediately by a rotational medicine ball throw. You might have to read that three times, but it is the simplest way I can describe what I saw. The issue here is the confusion created from adding too much complexity. The exercise often grows so complex that the skill it was originally intended to train (assuming rotational speed or single leg balance or single leg strength?) becomes so washed out that it is minimally effective, if at all.
Looking back on my early training experience while I was finishing up PT school, I was crushing the commercial gym scene with the “Tortured Trainer” approach. I wasn’t actually good at training people or writing programs to help them meet their goals. But I had a long client list as long as people liked me and were intrigued by what I was doing. The problem with this was that I had to keep making up new stuff to keep them interested and none of it was based in any sort of science or objective measure. It wasn’t sustainable and if I had measured, they probably wouldn’t have been as impressed.
Early in my physio career, I made the transition to the “Mystical Physio” approach—attempting to improve people’s movements with primal movements, rolling, minimal hands-on work, and nonexistent strength training. Again, I had a long client list and people actually thought I knew what I was doing. If I’m honest, I hit plateaus with many clients. (Basically, when they needed serious hands-on work or real strength training that I wasn’t doing).
In both cases above, I missed the middle ground and I had to learn it the hard way. Sometimes it is appropriate to add complexity to an exercise and other times neurological retraining can be magical. But neither one is ever the answer in isolation, and if you do too much of either, the results are counterproductive. They are all part of a larger training and rehab continuum; just as unstable surface training is. The more of us that can realize this, the better it will be for our athletes.
The golf performance world is improving every year and the research on unstable surface training is hopefully becoming clearer with this summary. No matter the sport or the athlete, the first place to start is always an individual evaluation to understand the demands of the sport and how well the athlete is prepared to meet those demands at a high level and without injury.
Regardless of your feelings on the above, we can all agree that the buck stops with performance on the course, field, or court.
Transference – Is It There?
At the end of the day, all of the research, training philosophies, and ideas in the world come down to one question: Does it transfer to sport? That is all that matters.At the end of the day, all of the research, training philosophies, and ideas in the world come down to one question: Does it transfer to sport? That is all that matters. Click To Tweet
In the world of golf, in particular, this tends to be an oversight. We tend to focus more on the “why we are doing an exercise” and “does it look like it trains the golf swing patterns.” There is a serious deficit of focus on “does this intervention actually move the needle in performance on the course?”
Coaches applying unstable surface training with a proprioceptive training effect in mind may in fact be impairing the development of important athletic qualities such as power, speed, and force output.4Power, speed, and force outputs will be trained at about 30% less force output compared to using stable surfaces, which is likely the cause of the development impairment seen when unstable surfaces are used. This suggests that if we want to focus specifically on proprioception training, it should be done on stable surfaces to assure strategies and patterns used in sport are used in training.
Examples of proprioceptive work that would not be detrimental to power, force, and speed outputs would be having young athletes working on proper single leg stance mechanics on solid ground while passing medicine balls to each other versus standing on one foot on an Airex pad passing balls. A dynamic example would be single leg hops or box jumps with focus on stable landing and take-off mechanics.
In adolescents and young adults, the specific comparison of stable surface training and unstable surface training resulted in contradictory findings. Thus, the use of unstable as compared with stable surfaces during strength training is not recommended in healthy adolescents and young adults if the goal is to enhance performance on stable surfaces.7This means that unless there is a specific injury or physical deficit in proprioception, keep the unstable surfaces in the closet for your junior golf fitness classes and your sport performance training.
There have been a number of other studies that have shown a very high statistical correlation of chest pass power, vertical leap power, total rotational power, and others to club speed, which is a direct sport performance measure.8,9In lieu of the unstable surfaces, look at your programming and training to work on training up the skills to improve the physical traits needed to excel in these areas of power production.What this all boils down to is that Bosu balls, physioballs, balance discs, and Airex pads should be kept in the rehab clinic. Train athletes on the stable surface they play on. Click To Tweet
What this all boils down to is that Bosu balls, physioballs, balance discs, and Airex pads should be kept in the rehab clinic. When the athlete enters the gym to train for sport performance, train them on the stable surface they play on. In the world of golf and most other sports, that means the ground (unless, of course, they surf or skateboard—then it is likely a different scenario). If you want to train stability and proprioception in the gym, do it on the ground and add proprioceptive challenges in terms of stance widths, external upper extremity challenge, and the like.
The next time you see a colleague having an athlete jump from Bosu ball to Bosu ball or integrating unstable surface training with high-level athletes’ performance programs, please initiate a constructive conversation to improve both of your practices. We need to work together in the sport performance world to help coaches and athletes understand that adding complexity to an exercise to make it look new and different doesn’t always equate to improved performance. We need to challenge ourselves and our colleagues to keep to a higher standard—one of measured transference to sport performance.
1. Romero-Franco, N, Martinez-Lopez, EJ, Lomas-Vega, R, Hita-Contreras, F, Osuna-Perez, MC, and Martinez-Amat, A. “Short-term effects of proprioceptive training with unstable platform on athletes’ stabilometry.” Journal of Strength and Conditioning Research. 2013; 27(8): 2189-2197.
2. Wirth, K, Hartmann, H, Mickel, C, Szilvas, E, Keiner, M, and Sander, A. “Core Stability in Athletes: A Critical Analysis of Current Guidelines.” Sports Medicine. 2017; 47(3): 401-414.
3. Behm, DG, Leonard, AM, Young, WB, Bonsey, WA, and MacKinnon, SN. “Trunk muscle electromyographic activity with unstable and unilateral exercises.” Journal of Strength and Conditioning Research. 2005; 19: 193-201.
4. Cressey, EM, West, CA, Tiberio, DP, Kraemer, WJ, and Maresh, CM. “The effects of ten weeks of lower-body unstable surface training on markers of athletic performance.” Journal of Strength and Conditioning Research. 2007; 21(2): 561-567.
5. Chulvi-Medrano, I, García-Massó, X, Colado, JC, Pablos, C, de Moraes, JA, and Fuster, MA. “Deadlift muscle force and activation under stable and unstable conditions.” Journal of Strength and Conditioning Research. 2010; 24(1): 2723-30.
6. Behm, D and Colado, JC. “The effectiveness of resistance training using unstable surfaces and devices for rehabilitation.” International Journal of Sports Physical Therapy. 2012; 7(2); 226-41.
7. Behm, DG, Muehlbauer, T, Kibele, A, and Granacher, U. “Effects of strength training using unstable surfaces on strength, power and balance performance across the lifespan: A systematic review and meta-analysis.” Sports Medicine. 2015; 45(12): 1645-1669.
8. Finn, C., Prengle, B. and Cassella, A. Research Driven Golf Performance Training, Par4Success. October 2018, pp. 3-20.
9. Finn, C., Prengle, B. and Cassella, A. Eccentric Flywheel Training and Its Effects on Club Speed in Golfers: A 6 Week Study. Par4Success. April 2019, pp. 2-10.