The Role of UST with RT

April 12, 2018by IamAdmin

and what science has to say about this…?

Continuing from my previous article on Unstable Surface Training (UST) (Click for Part 1 of this series) with practical applications as myself serving as test subject. In this second part, I have looked towards what science has to say on this controversial topic at hand!

I have searched papers with this criteria: “Resistance training on unstable surface with elite level athletes”. Among many papers on UST I chosen only a few of them to get to my search criteria.

I must mention, that there are not many papers on elite level athletes so we should not make definitive conclusions after reading this.

I predict that this popular training modality has no future going forward!

Let us start with a quote from the one and only Big John: “Let’s get it on!”


Many entertrainers and circus performers are using different balls for many years to amuse people. Training on US is very common these day. When and how this modality came into our sporting environment is uncertain. We can assume that probably from Physio therapy where Swiss and German therapists used them in their therapeutic environment before WW2 (1).

Proponents of instability Resistance Training (RT) deduce that greater instability on US and human body interface will stress the neuromuscular system to a greater extent than traditional RT methods performed on solid surface (2).

Also, there is common thinking that RT performed in unstable body positions have been hypothesized to increase both muscular strength and endurance of the core musculature, which may translate to more powerful and efficient movement patterns and less risk of injuries (3).

The importance of neuromuscular training such as training on a US is of huge importance for proponents for this kind of modality. Strength gains can be attributed to increases in cross-sectional area in muscles and neuromuscular coordination. Neural adaptations has the most important part early in strength gains in RT (2).

According to Rutherford and Jones (4) specific neural adaptations was not increased during training and recruitment or activation of motor units. Improved coordination of agonists, antagonists, synergists and stabilizers were recorded. This leads us to assume that UST is a way to train for strength improvement?. Hmmm, this is from a paper more than thirty years ago. There must be something more up to date on this topic?

There are several factors to determine stability considering RT exercises (3):

  • Base of support: stable vs. unstable surface,
  • Body position: standing vs. seated vs. lying,
  • Type of equipment used: free weights vs. machines,
  • How the exercise is performed: unilateral vs. bilateral.

Sport Specificity

A lot of authors and trainers I guess think that training on US is sport specific as there is a lot of moments in sports where athletes are on uneven, unstable, slippery surface: wet grass, ice, ski slope… so for they must include UST into their training regime.

All this comes from a point of view that athletes must be balanced all the time during their training and competition. They mistakenly confuse training for strength and balance and want to combine the two together!

In contradiction to the concept of training specificity, most sports involve dynamic balance, whereas instability RT is typically under relatively stationary conditions. If training in static stability will effectively transfer to the dynamic stability is still debatable (1). That is why we must not jump too fast and conclude that UST to be sport specific training.

After reviewing many articles about this, next sentence from Willardson (in 1) must be the most worth to remember: “The optimal method to promote increases in balance, proprioception and core stability for any given sport is to practice the skill itself on the same surface on which the skill is performed in competition.”

Behm et. al. (in 3) concluded that experienced ice-hockey players didn’t do better after training on US (wobble board). Their speed on skates wasn’t any better. Again they mentioned in their conclusion that training on wobble board requires static balance comparing to dynamic balance on skates and that this is like comparing apples and pears.

In the paper from Stanton, Reaburn and Humphries (in 3) rugby and basketball players didn’t improve running performance after training six weeks on Swiss ball (also physio, stability or big ball).

In research done by and Cosio-Lima et. al. (in 3) they wrote that: “Whether Swiss ball exercise provide the specific training adaptations that could be used by elite athletes demands further research.

Some authors do endorse unstable surface training for sport specific training, often without any backup to reinforce their claim. Hydren et. al. (6) writes that alpine skiing is characterized by the instability with ski snow contact especially in soft snow. How often do the best skiers have soft snow conditions? Almost never, as the ski slope controller would not give his approval to race on such a slope. They proceed with saying that: “The purpose of strength and balance workouts is to improve motor patterning for unstable conditions through neurologic adaptations”(6). Their reasoning is that with UST they encourage the neuromuscular side of training. Which is in line with what Behm writes (By the way they did include his paper and this was the only paper they provided! I wonder if this is right or wrong?).


Picture 1: Picture acquired from this link.


For conclusion we already know that we must differ from static vs. dynamic stability training and that we have to train on the same surface as we compete if we hope for some transfer in sport specific training.

My conclusion is that we can’t conclude that training on US can guarantee better sports performance on the field, track, slope… if anywhere! Movements in sports are too fast and training slow could not be sport specific.


Training on UST and effects of this kind of training have on core performance must be the most researched point of view of UST and probably only one that has positive outcome.

Cosio-Lima et. al. (in 1 & 3) write that untrained women did have significantly improved core muscle activity after performing exercises on Swiss ball vs. conventional floor exercises after five weeks of training. Same conclusion have Vera-Garcia et. al. (in 3) with untrained men who almost doubled their abdominal muscle activity performing curl-up exercise on Swiss ball vs. on stable bench. The same have found Behm et al. (in 3) in their research with recreational trained men and women who exhibited significantly greater lower abdominal muscle activity while performing unilateral dumbbell chest press on Swiss ball.


Picture 2: Original picture available at this link.


Willardson (3) conclusion is that research supports the effectiveness of RT exercise performed on US for increased core muscle activity with untrained or recreational trained women and men, the same might not be true for elite level athletes.

Many special trunk exercises performing on US has benefit of it because of greater trunk activation. Anderson and Behm (in 1) found the same while subjects performed squats on US exhibited 20–30% greater activation of trunk stabilizing muscles.

In quite thoroughly and not that old from 2007 research done by Norwood et. al. (7) they hypothesized that performing exercise on US, which stress the synergistic and stabilizing muscles around a joint, provides more specific and functional form of training. They confirmed this with results in their paper as their subjects performed bench press on four different surfaces: stable (flat bench), upper body unstable (back on Swiss ball), legs unstable (legs on Bosu), unstable (legs on bosu and back on Swiss ball) the more unstable the surface the greater the EMG activity of stabilizer muscles. They conclude that performing exercises on US is more beneficial for trunks stabilizers than prime movers.

Qualitative numbers

Concerning different qualitative numbers representing training on US and Stable surface (SS) from different papers respectively matched my own research, which I presented in my previous post (LINK).

Gruber et. al. (8) found in their work that exercises on SS have bigger RFDmax pre and post 4-week training than those on US. Both groups did elevate their respective RFD on SS compared to US. Much greater were the SS group where post training numbers were 48% higher post vs. pre training, whereas US group did have greater RFD numbers but for only 14%. Both groups improved because of decreased time to reach RFDmax. This research did have a control group and their numbers didn’t change which is good, but, what I disliked was that the exercises were different for US vs. SS group. So the comparison between groups is not something to look for. Again this study was done on untrained men and women and we must use this finding cautious as probably those numbers on both surfaces with trained athletes would be lower from pre to post 4-training.

In another study looking for qualitative numbers Kieble and Behm (5) wrote that a number of studies documented that lower forces were produced performing exercises on US and that training on US with resistance exercises produces lower force output (in some cases even for 60–70%) in upper and lower body exercises and power output too. This goes along with my own findings in previous post (

Mate-Munoz (9) looked for difference in strength, power and speed. They tested untrained women and men with exercises: squats, bench press, SJ and CMJ. Traditional RT group did regular exercise performed in fitness centers: lat. Pull down, lunges, DB incline press, seated rows, step ups… and Instability group did similar exercises on bosu and with TRX. After seven weeks of training the main finding is that both groups induced similar effects after seven weeks of training. I must mention that again we can’t quite compare this findings as the exercises were different.

I have looked hard to find some studies done with experienced athletes. I must say there aren’t many. Here is one from Serbia (10) done on judo athletes with an average 10 years of experience in sport. The researchers found a difference between those tested on US vs. SS is in favour of those on SS meaning their numbers are higher. They have looked into power output and velocity performed in squats and bench press on US and SS. Their conclusion is that bench press power output (5,1%) is of lesser difference beatween US and SS from squat power output (31,2%). Which confirms a theory that US has lesser impact on upper body exercises than those on lower body from elsewhere in this article. I presume less moving body parts involved and less body mass involved.


Balance is another aspect that exercising on US has the biggest impact on (beside the effect on core/trunk muscles) (5). For more on balance read above in sport specificity chapter.

Injury prevention and rehabilitation

The strengthening of a trunk or core stabilizing muscles is an important consideration for activities of daily living and rehabilitation and back pain. Increased back strength is not necessarily associated with the prevention of LBP. However a lack of back muscle endurance is strongly associated with LBP. Abenhaim et. al. (in 1) states that there is general agreement that resistance exercise is beneficial in the rehabilitation of LBP. It is common practice that for trunk/core strengthening and rehabilitation exercises are done on US. It has been proposed that the demands of an US will cause an increase in muscle activation in order to complete the exercise in a controlled manner (1).


Picture 3: Injury prevention training, hmmm? Picture from this link.


If you are an S&C coach and your athletes are doing this, at least for me, inappropriate exercises mentioned throughout this text (Resistance training on US) and they are performing well does this lead to the conclusion that your choice of exercises is correct? Maybe you are working with exceptional athletes that no matter which exercises they do, they could do it right and will be useful for them!

Behm (11) state in their conclusion that training priority on US need not to be on significant strength gains but to improve balance, stability and proprioceptive capabilities.

From practical standpoint we can use sometimes UST for diversity in resistance training with inexperienced resistance trainees, as more experienced athletes need greater resistance in % of RM to improve their strength levels.

If we choose such training modality then we must acknowledge that it is better done with upper body exercises then lower body. Challenging balance-stability with unilateral work is better option than performing exercises on US from a resistance training point.

The coach must realize that with training on US their athletes won’t improve in power, velocity and RFD section enough which is mentioned in many papers as this is the part that makes difference in the sport arena. If this was true why we don’t see that in weightlifting/powerlifting or even in bodybuilding gyms?

It is not the point of this article that I want you, as a coach, to change your opinion I just want to share some knowledge that is a bit hidden and because some still use common knowledge “I did it, so it must be the best way”.

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  1. Behm, D.G. and Anderson, K.G.: The role of instability with resistance training, Journal of strength and conditioning research, 2006.
  2. Behm, D.G.: Neuromuscular implications and applications of resistance training. Journal of strength and conditioning research, 1995.
  3. Willardson, J.M.: Unstable resistance exercises, from
  4. Rutherford, O.M. and Jones, D.A.: The role of learning and coordination in strength training. Eur. J. Appl. Physiol., 1986.
  5. Kibele, A. and Behm, D.G.: Seven weeks of instability and traditional resistance training effects on strength , balance and functional performance. Journal of strength and conditioning research, 2009.
  6. Hydren, J.R., Volek, J.S., Maresh, C.M., Comstock, B.A., Kraemer, W.J.: Review of strength and conditioning for alpine ski racing. National strength and conditioning association, 2013.
  7. Norwood, J. Anderson, G.S. Gaetz, M. Twist, P.: Electromyographic activity of the trunk stabilizers during stable and unstable bench press. Journal of strength and conditioning, 2007.
  8. Gruber, M. Gruber, S.B.H. Taube, W. Schubert, M. Beck, S.B. Gollhofer, A.: Differential effects of ballistic versus sensorimotor training on rate of force development and neural activation in humans. Journal of strength and conditioning, 2007.
  9. Mate-Munoz, J.L. Monroy Anton, A.J. Jimenez, P.J. Garnacho-Castano, M.V.: Effects of instability versus traditional resistance training on strength, power and velocity in untrained men. Journal of sports science and medicine, 2014.
  10. Bratic, M. Radovanovic, D. Ignjatovic, A. Bojic, I. Stojilkovic, N.: Changes in the muscular outputs of young judoists during resistance exercises performed on unstable equipement: a case study. Archives of Budo, 2012.
  11. Behm, D.G. Anderson, K. Curnew, R.S.: Muscle force and activation under stable and unstable conditions, Journal of strength and conditioning research, 2002.