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The Science of Speed Part 3 – Reduced Antagonist Coactivation

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Before getting into this adaptation I must explain some terms.
When we carry out a particular movement, there is often one main muscle group or “prime mover”. This is known as the agonist muscle for that movement. For every agonist, there is an antagonist, which is the prime mover when moving in the opposite direction. At a particular joint, the shortening of the agonist and antagonist muscle would produce force in opposing directions.

A simple example of this is the elbow joint, bicep, and tricep. To bend / flex our elbow, the agonist is the bicep. The antagonist is the tricep. This can also be reversed. To straighten / extend our elbow, the tricep is the agonist, and the bicep is the antagonist.

It was originally thought that when an agonist contracted, the antagonist would relax, through something called reciprocal inhibition. As more research was carried out, it became apparent that there was actually some contraction of the antagonist. This is how we get the term “Coactivation”. (1)

If we are trying to produce force in a certain movement, but also have the antagonist muscle producing some force in the opposite direction we are going to have less net force in the direction we want. This is usually referred to as “net joint torque”, but I don’t think we need to get too deep into technical terms (and I might misspeak!!).

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Generally, the process of coactivation works as follows. We initiate force production in a certain movement using the agonist muscle, then there is a rise in antagonist activation (reducing net force), followed by a lowering of antagonist activation. Coactivation is beneficial for joint stability, and may help with precise control of fine movement (2). It may also be some sort of inbuilt safety mechanism, that in untrained people is set a little too high to allow maximal outputs.

Coactivation is not a “bad thing”, however too much of it is potentially limiting our force output in certain activities. It is also more prevalent in activities where the person is trying to move as quickly as possible (2). Logicially, it seems that when trying to create maximum force with certain muscles during the golf swing, we don’t want the antagonist producing a force in the opposing direction, slowing us down!

This topic has been investigated by a number of different studies and it suggests that skilled performers in certain tasks have learned to reduce the level of coactivation, aiding performance (3). It is important to note that this reduction in coactivation, as with most nervous system adaptations, is velocity specific (4,5), and probably movement pattern specific. A movement pattern that looks similar, like golf swings at easy speed versus maximum speed, probably have some differences in motor strategy. Just like jogging and sprinting do, even though they are both running.
As a result I think speed training has different nervous system and muscle adaptations compared to “normal” golf practice.

As I touched on in Part 2 of this series, about Rate of Force Development (RFD), a lot of studies are done in isometric single joint exercises. For example, a leg extension or leg curl against a pad while sitting in a chair. This makes it challenging to extrapolate what it means for a very complex movement involving LOTS of different joints working in harmony as in the golf swing.


What’s the takeaway?

Reducing antagonist coactivation is likely one (of many) of the nervous system adaptations that occur when we start speed training, that enables us to swing faster.

One particular research study I read reported that reductions in coactivation are a nervous system adaptation that occur very quickly (maxed out after 1 week of training), and account for about 10% of the total improvement in maximum force (6). Again, this particular study was done in an isometric exercise on a single joint, so it is hard to guess what it means for training the golf swing.

Based on my research, it seems clear that a reduction in antagonist coactivation is one of the beneficial adaptations we get from speed training. I think how we tap out its potential very quickly, and that it’s not really a very significant contributor to long term gains in club head speed. In coming articles, I will try to cover topics that are more trainable and lead to bigger improvements in the long term.

A recurring theme in this series will be “to get better at the thing, you need to do the thing”. In this case, it’s practicing swinging as fast as we can. Make sure you have a radar recording all of
your swings in speed training to increase motivation, incentivise experimentation with slightly different swing strategies, and provide feedback on whether you are actually getting faster or not. I highly recommend the PRGR Radar from SuperSpeed golf. You can get 10% off with the code fitforgolf23.

Hopefully you are enjoying learning about the different reasons behind why certain aspects of a training program are incorporated, and how exactly they are changing us to enable better performance.


References:
1) AM;, S.The coactivation of antagonist muscles, Canadian journal of physiology and pharmacology. U.S. National Library of Medicine. Available at: https://pubmed.ncbi.nlm.nih.gov/7032676/ (Accessed: January 14, 2023).

2) Latash, M.L. (2018) Muscle coactivation: Definitions, mechanisms, and functions, Journal of neurophysiology. U.S. National Library of Medicine. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6093955/ (Accessed: January 14, 2023).

3) Bazzucchi, I., Riccio, M.E. and Felici, F. (2008) “Tennis players show a lower coactivation of the elbow antagonist muscles during isokinetic exercises,” Journal of Electromyography and Kinesiology, 18(5), pp. 752–759. Available at: https://doi.org/10.1016/j.jelekin.2007.03.004.

4) Pousson M;Amiridis IG;Cometti G;Van Hoecke J; (no date) Velocity-specific training in elbow flexors, European journal of applied physiology and occupational physiology. U.S. National Library of Medicine. Available at: https://pubmed.ncbi.nlm.nih.gov/10483808/ (Accessed: January 14, 2023).

5) Duhig, S.J. (no date) “Hamstring strain injury: Effects of high speed running, kicking and concentric versus eccentric strength training on injury risk and running recovery.” Available at: https://doi.org/10.5204/thesis.eprints.110637.

6) E;, C.B.C. (no date) Adaptations in coactivation after isometric resistance training, Journal of applied physiology (Bethesda, Md. : 1985). U.S. National Library of Medicine. Available at: https://pubmed.ncbi.nlm.nih.gov/1400055/ (Accessed: January 14, 2023).