There seems to be an assumption in the world of athletic training that bilateral exercises such as deadlifts, squats or cleans will automatically lead to an athletic, strong and symmetric body and thus must be beneficial for the athlete. But is this really true?
Unfortunately, in most cases the athlete’s brain initially prefers one side of the body and will use this side to a greater extend – even in a bilateral exercise. But for what reasons does the athlete rely more on one side during movement and exercise? Well, grossly simplified it could be one or all of the following:
- 1. the brain receives a greater amount and/or more clear information from one side of the body (proprioceptive input)
- 2. the brain areas that integrate and coordinate movement are less active and accurate (cerebellum)
- 3. and at least one side could have better reflexive stabilization (brainstem).
Please remember, the brain always – always – seeks reliability and predictability on what is currently happening and on what is going to happen next. In an athletic setting this is particularly important since the body is under extreme stress! In addition, stress is by definition always a potential Danger/Threat to our system and if our nervous system classifies something as too threatening it will refuse to participate. Instead it will engage some survival based reflexes to protect the body. A lack of predictability might therefore not only intensify asymmetric movement patterns (as seen below) but also lead to a threat response.
The goal in athletic training is to perform better – not just get stronger
So, if the cerebral areas which control muscle tone and reflexive stabilization and the cerebral areas which control motor coordination are not developed and/or activated equally on both sides, the brain will always align the movement in an altered way to engage those areas that provide more and better information. In most athletes there will be a side which already shows a lack of coordination and because of the neural activation patterns in the brain the opposite side shows up with aberrant muscle tone or lack of reflexive stabilization (due to a lack in brain activity). Yet, during bilateral exercises one continues to try and stress it the same way as the „better“ side. Not a good idea at all! In consequence, those structures, which the brain perceives to be more predictable are relied upon more and more in movement and performance. And those are the structures that continue to develop and get stronger.
Now, the athlete might indeed improve within the practiced exercises (cleans, dead lifts, etc.), but more on the basis of improved coordination and technique within the available structures – those parts that are under control via the CNS. Simply put: the athlete gets better in using what he already uses more (the better coordinated side and a few structures from the less coordinated side), while the “weak side” the side with less control and coordination has to compensate more – and revert to the (few) available structures. Thus, the compensation pattern gets even more distinct and the athlete develops into being better in compensating.
Those compensation structures can (sometimes) become very powerful and as long as we are focused on measuring quantity we might be lead to believe the athlete truly improved – just because he is now able to lift more pounds. But: NO!!! He only got stronger in those particular exercises, that’s all – and that again has almost no or just very little carry over in regards to sports performance enhancement. As trainers, we must not neglect the “law of the specificity of adaptation (to the imposed demand)”- the SAID principle. Meaning, that (unfortunately) the athlete always and exactly improves only in the respective exercises he engages in, but not or just little in his sport specific athletic performance. This is a well-known fact we can’t overlook. The sole objective of neuro-athletic training should be to improve sport specific athletic performance!!
But: back to our bilateral training. If we see just a few, if any, technical mistakes we might be lead to believe that everything is running smoothly – and, exercising out is so simple that you can’t mess it up, right?! That it absolutely wrong. A fallacy actually, since the movement continues to be a compensation mechanisms – one that you are loading!!! And even more dramatic, if one side – or certain structures within one side – continou to be used more extensively during bilateral strength training over time this alters the activity of the involved brain areas. Some brain areas get more and more active while others degrade – that’s the rule of neuroplasticity: use it or lose it. With all that said it should not come as a surprise that the injury potential increases distinctly, since these are only substitute structures that have to fill in, while the optimal, natural structures cannot be triggered adequately via the CNS and the athlete’s brain function is being altered into getting better in compensating. Really not clever!
We must not forget that the forces transferred through the body during running, sprinting and directional changes are sufficient to provoke an injury – without any outside influence! It is therefore very well possible that motion-induced injuries are partly caused by outdated training systems as well.
The Sad Reality – the Brain is Excluded in Classical Approaches
Indeed, we all want symmetry – or two well-developed sides of the body. However, we should not permanently work bilaterally, or only in very rare cases! In “classical training systems,” athletic training is often based on bilateral movement patterns – yet these systems do not check for how and whereby which side of the body has to be trained further or differently in order to achieve an activity balance between the cerebral areas as a necessary prerequisite. Therefore, when implemented into training, the muscular tonus pattern, the reflexive stabilization and the coordination and control of the body sides become increasingly asymmetrical. Simultaneously the risk of possible injuries during regular exercise increases.
If the athlete or trainer has the opportunity to test the different brain areas for their activity level and their neuronal answer to unilateral training (our advice here would be to seek and find a fully certified Z-Health Trainer) the – at least temporary – training of just one side would be of distinct benefit to most athletes with respect to injury prophylaxis and performance enhancement, in comparison to a bilateral training approach.