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In a number of sports athletes compete in weight categories. Most of these sports are martial arts, where it is considered unfair for a bigger (and heavier) athlete to fight a smaller (and lighter) athlete.


On one hand this system opens top-level competition to athletes that would otherwise be too small to compete, but on the other hand it means athletes face the issue of “cutting weight”. The advantage obviously goes to the heavier athlete, meaning it is beneficial to compete at the top end of each weight category. This leads to a situation where athletes who are significantly heavier than they compete at, will drop lots of weight the run up to an event. Cutting weight is done differently in each sport, but usually includes sweating large volumes the day before an event, often by simply exercising wearing lots of layers! While this practice is within the rules, it can be dangerous to the athletes if they are undertaking extreme weight loss, or simply be detrimental to performance because:


  1. If athletes are only armed with the knowledge of how much weight they must cut it is very tricky to judge exactly how much exercise, and at what temperature, is needed to achieve this. Because of they want to be on the safe side, athletes often lose more weight than necessary, which puts them at a performance disadvantage.
  2. In the build up to a competition, when athletes should be mentally preparing themselves they are instead focused on their weight. This is an unnecessary distraction that athletes just don’t want!
  3. If an athlete who hasn’t trained their sudomotor system tries to lose significant volumes of sweat they will suffer all the negative effects of dehydration, including; raised heart rate, reduction of blood volume, fatigue and impaired decision making.


This is where Kudu comes in to save the day.


With regular use of the Kudu we have been able to build up a “sweat profile” of our athletes, showing how that athletes sweat response acts. When this data is combined with weight loss during a training session, we can see how much exercise causes a given weight loss. This means that during the process of making weight, athletes can make informed decisions about how much exercise is needed to cut a certain amount of weight. It also removes the mental stress of worrying, and having to make decisions when they should be focused on the upcoming competition.


In the future this could be incorporated into the Kudu app. Athletes can log into their account and input the weight they need to cut, then exercise while wearing the Kudu and the app will notify them when they’ve sweated enough. This means that athletes can have significantly more detailed information during the cutting weight process.


So, let me tell you about how we’re working with a team of lightweight rowers and are planning to improve their weight cutting practice. The rules for lightweight rowing state that the maximun average weight for a female crew is 57kg (with no individual over 59kg), and the maximum average weight for male crews in 70kg (with no individual over 72.5kg).  


The fact that any individual athlete can be up to 2.5kg over the average crew weight gives rowing a unique weight cutting element. Imagine a situation where every athlete in an 8 person crew weighs in at 70.5kg. They’d have to lose 4kg between them, but that weight loss can come from any of the rowers. By comparing each athlete’s sweat profile, which tells us how fast and strong their sweat response is, the Kudu team can advise how this 4kg should be cut. Rather than asking each rower to cut 0.5kg, which may be a considerable challenge for some of the athletes, we could take the 4 rowers with the strongest sweat response and tell them to cut 1kg each, which wouldn’t be too much of a challenge for the 4 best sweaters.


By working as a team, with each member playing to their strengths, the crew are able to cut the weight, and perform at their best.

As the most recent addition to the Crossbridge Scientific team I’ve been learning quickly what we’re all about. The aim of the company is ‘to put the “science” into sports science’, which, as a sports science student is obviously a mantra I’m on board with. The world of sport has got increasingly scientific in recent decades, with significant steps forwards in areas such as nutrition, psychology and of course Crossbridge’s area of fitness measurement.

For me personally the innovation here at Crossbridge is particularly interesting because it ties in so well with my time as an endurance runner. In September 2016 I ran the Oslo marathon in 2:42, cutting a massive 21 minutes of my previous pb. I achieved this through a significant change to the way I trained and recorded my running. I moved towards running lots of “hot and slow” miles, and recorded as much data as possible. I could discuss for hours the benefits how I trained but I’m instead going to tell you why recording as much data as I could was a great choice. Courtesy of Dr Schwiening, part of the Crossbridge team, I was provided with a spreadsheet into which I input the time, distance and average heart rate for all my training runs. From this information I was then presented with a range of graphs, charts and numbers, each showing me something new. One of the most useful graphs was the distance vs intensity graph. Which, by the end of summer 2016, looked like this:

Here the red line is a measure of the intensity of my training, and the blue line shows how far I’m running each week. This graph is cleverly used to avoid injury. Training at an intensity that’s too high is a huge source of injury for runners, but by plotting this graph I was able to check I wasn’t training too hard and therefore avoid injury. If the red line strayed above the blue line I knew I had to run for a few days at a lower intensity so that I wasn’t ramping up the intensity too fast. All I had to do was keep checking this graph, adjust training accordingly, and hey-presto; injury avoided!

This is just one example of how becoming a data driven athlete has helped me improve, but, there are ways that data will assist in any sport. It might be fairly complex, such as a kinematic analysis of your tackling in football or it could be more simple, like recording how far you run each week, but either way the point is that data can help all athletes and generally speaking a good ethos to follow is that more data is better.

This is essentially what Crossbridge is all about. At the moment there is no way for an athlete to measure and record sweat rates and monitor thermoregulatory efficiency over time. Crossbridge developing this world-first wearable, real-time sweat rate monitor has great implications for the world of elite sport and, personally, I’m very excited to get hold of of a KuduSmart®, go for a run and see how good I am at sweating.

Let’s talk about running. Specifically, running a long way in a hot environment.

From an evolutionary perspective humans are exceptionally well designed to disperse heat from their bodies. We cool ourselves in a fundamentally different way to other mammals - when other animals pant, we sweat. Panting cools animals by bringing air at environmental temperature into the lungs, which is then heated as it passes through the respiratory system, and expelled at a hotter temperature than it arrived to the body at.

The human cooling system on the other hand works mainly by pumping hot blood to the surface of your skin, and this blood is then filtered to become a protein-free, hypotonic plasma filtrate (that’s just blood with the red blood cells, proteins and (most) the salt taken out). This then moves out of your body through your sweat glands and is seen by you as sweat. As sweat evaporates it cools you down.

The human method of cooling has a number of advantages for exercising in hot environments, primarily it allows humans to shed a huge amount of heat into an environment that is already very hot, such as sub-saharan Africa. In short this affords humans a unique ability to exercise in the heat. Also, due to the fact it is such an efficient cooling system, it allows us to exercise for a longer amount of time than many other animals.

In much the same way that athletes train their heart and muscles, the sweating system is can be adapted - there is a whole system working here within the human body that is very trainable, but predominantly ignored by athletes. By exercising “hot” - either in a warm environment or by wearing a jumper & hat - your sweat response changes. Sweat glands become larger and better at re-absorbing the salt in your sweat, while your brain starts your sweat response at a lower body temperature. When trained both of these adaptations make exercise in the heat easier.

What this means for you as an athlete, sports scientist or coach is that you have just been introduced (or reminded if you already knew this stuff) to a physiological variable just as important as any other measure, such as body fat or resting heart rate. Now you know how all about sweat that you can now specifically tailor your training to when necessary. In the lead up to a match / race / competition that you know will be hot it’s smart to change your training accordingly.

From a personal level I saw the importance of this during the Leeds Half Marathon 2016, which was run on a very hot day in May. Generally speaking British runners are not very well adapted to the heat and this can be seen by comparing the finishing times in the 2016 race to the 2015 and 2017 results. If you look at the average finishing time for the top 50 runners you can see that the 2016 race was significantly slower than the years before and after it.


Average Finishing Time (first 50) 1:18:57 1:21:00 1:19:51

(The top 5 finishers each year were removed from this since they are very well adapted to the heat so unnaffected by the hot conditions)


On a more anecdotal note I was able to see this in the way other people looked out on the course. Having done lots of “hot” training in the lead up to the race I had a very good sweat response, but most of the runners had been training in the spring, in Yorkshire so were not well adapted to the heat. In the last 15 minutes, when the sun was hottest, I was noticed I was consistently passing lots of other runners,  many of whom I knew would have beaten me on a cool day. An added benefit to having good thermoregulation was that I didn’t require a long recovery time after finishing. In fact within a few minutes of crossing the line I had met a friend in a pub close to the finish line! So, the lesson here is clear; by specifically training your sudomotor system in order to create a more severe thermoregulatory response you can get to the pub earlier - although this probably does mean the first round’s on you...