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Writer's pictureCoach Jamie

The Effects of Hypohydration and Rehydration on Neuromuscular Performance in Combat Sports Athletes

As some of you may be aware, over the last 4 years I've been completing a masters part time in strength and conditioning. This week was the final hurdle, and now after submitting my research, it is all over! For those interested in what I've been doing over the last 8 months specifically, you can check out the conference poster below, or download the pdf poster so you can zoom in!


A quick summary for those who aren't familiar with the practice of 'weight cutting' in combat sports; Weight cutting can encompass many methods which aim to reduce an athletes body mass leading up to competition. Typically, due to the considerable volume of water in the human body, undergoing acute dehydration practices 24-48 hours prior to competition is the primary mechanism to induce rapid weight loss. This can be achieved by active (exercise), passive (environmental thermal strain e.g. sauna / hot bath) or often the combination of both methods. The end result is "hypohydration" or more simply put, a state of water deficit.


The question to those outside the sport looking on is "why?".


Combat sports, much like weightlifting, have weight categories so that competition is fair. For example, if all things were equal in regards to skill, you couldn't have a heavyweight compete against a lightweight because of the strength and size difference. The idea behind weight cutting then; by acutely reducing body mass to achieve a lighter weight category, one could achieve a competitive advantage. This is because once a fighter has 'weighed in' they typically have some time to rehydrate and return back to their normal weight. This practice is commonplace, it is widespread throughout all combat sports.


Although smaller magnitudes of hypohydration (<2% of total body mass) are unlikely to affect performance in combat sports, athletes are accustomed to losing 5-10%. There is evidence to suggest that this can increase the chance of a winning outcome, and it is well established that some of the best competitors in the world go through large weight cuts (>7% of total body mass). However when everyone does it, and when you consider how many variables contribute to a winning outcome, it is extremely hard to isolate its impact. It is important to remember performance is not the same as outcome, athletes can perform terribly and still win, this creates a problem. If a fighter loses 10% of their body mass and feels awful, performs terribly but still wins, is it all forgotten?? Additionally, when people believe there is an advantage to be had, they will go even further to the extremes, and unfortunately there can be severe consequences. For those interested in what those potential physiological consequences are, this is a great case study where an athlete lost 9.3% of total body mass in 24 hours.



It has been reported that 80% of athletes who have partaken in weight cutting have claimed it has not gone according to plan at least once. There is greater concern when a lot of these athletes do not have qualified experienced practitioners overseeing this process. What is of little deliberation is the greater the weight cut, the greater the performance decrement and the potential for negative impacts on health short, and long term. This is why it is critical for research to continue to demonstrate what happens to performance post weight cut, so we can make better qualified and informed decisions. This was the primary motivation for the research. Specifically looking at the reductions in strength, power and the effects on the central nervous system across multiple time points whilst controlling for rehydration.


Have a look at the poster to see what the study entailed, the results and my conclusions!


This was also part of a bigger project (secrecy for now!) which hopefully over the course of the next year you will be able to read the whole paper in a journal! So stay tuned.


Because this is just a conference poster with only the most important information available, any further questions about the study shoot over an email at jamie.scottperformance@gmail.com









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