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Dehydration? What is it and how does it affect your performance?

Dehydration? What is it and how does it affect your performance?

Picture this: it is a humid, hot day out on the sports ground. The warmup has just commenced, and you are already dripping with sweat. By half time your jersey is soaked, and you can’t concentrate to save yourself. By fulltime, you sit down and throw down as much water as you can but can’t seem to get rid of the headache that plagued you through the second half. This is the all too familiar scenario for the Australian athlete and are symptoms of dehydration. Dehydration is caused by an imbalance of fluid intake vs loss throughout any period and can have devastating effects on performance.

Dehydration of as little of 2% fluid loss in physical activity can have significant impacts on

performance. This article will take you through the ins and outs of dehydration and how to plan strategies for training and game day to make sure you can perform at your best!

What is Dehydration and Sweating?

Dehydration regarding sport can be termed as the loss of fluid from the body during physical activity.

This occurs through many pathways, mainly sweating. Sweating is a process used to thermoregulate (fancy way of saying keeping cool) the body during times when temperature may rise. This increased temperature is caused as a by-product of muscle contraction (movement) and is a normal physiological response. The energy created in the exothermic (releases energy) reaction of movement is translated to the sweat on the skins surface, cooling the body.

This process is highly effective and is aided by pathways stimulated in the brain such as vasodilation (increased blood flow). Everyone has experienced this in the past, regardless of whether it is during sport or not. Now, excessive sweating causes for fluid to be removed from the system (your body) and without it being replaced can lead to a deficit and an array of issues. These deficits can be significant, with studies on marathon runners finding up to an 8% loss in body weight in some subjects. Now that we understand how and why the body loses fluid during exercise, let’s look at why it’s bad.

Effects of Dehydration

There are two major impacts that result from dehydration. These being, decreased blood volume and cognitive function. Decreased blood volume has two major effects, compromising cardiovascular output and temperature regulation (sweat efficiency). Compromising cardiovascular output decreases the amount of blood available to fuel muscles with oxygen (used in aerobic metabolism) and remove waste products (such as acidic bioproducts from anaerobic metabolism). This compromising of energy systems hinders performance as it decreases both high and moderate intensity performance. The cognitive aspect of dehydration is particularly interesting as it affects how hard you as an athlete perceive the activity to be.

This puts a greater strain on the psychological aspect of sport, meaning although you may be able to compete at a certain level, you feel as if you cannot. It also affects decision making and some proprioception, increasing the risk of falls and injuries. Essentially, dehydration makes you work harder, with a lower capacity and without the ability to make well thought out decisions on the field. These impacts are found in as little as 2% decrease in body weight over the course of physical activity and with studies finding up to 8% loss regularly occurring in endurance events, this could potentially cause for huge performance losses.

How to Stop Yourself from becoming Dehydrated

The simple answer is replacing fluid lost through water consumption during the activity. Your body has a regulation tool for monitoring fluid levels within the body and this is your blood pressure. It works highly effectively in most scenarios with a thirst mechanism indicating you are dehydrated and increased urination being hyperhydrated.

However, unfortunately the world is not a simple place and some further guidelines have to be in place. First, an analysis of what type of activity, the duration, intensity and environment competing in must occur. Obviously, someone competing in a triathlon in 40-degree weather is going to need a larger overall consumption compared to someone

in a 100m sprint. Below are some guidelines to follow surrounding training and competing.

Prior to Training or Competing

Attempt to ensure that you are hydrated leading into the event. This can be self-regulated through drinking to thirst for most or completing a USG for you hardcore athletes. USG’s or urine specific gravity are tests that can be done to analyse the level of dehydration objectively and levels above 1.020 indicating some level of hypohydration.

During Training or Competing Intra-event strategies are ultimately dependent on the duration and environment that you compete in. Common sense prevails in these circumstances. If the temperature is above 30-degrees or is above what you would normally train or compete at, it is likely that an interspaced drinking strategy may be beneficial to you. The same can be recommended for long duration events, with sports such as triathlons requiring specific focus as fluid cannot be consumed during the swim component. However, for shorter events (less than 60 minutes) in cooler weather (below 30-degrees or typical training environment), drinking to thirst has been found to be an effective strategy. Some other guidelines to follow are:

1. Limit fluid intake to small portions frequently – nothing is worse than trying to run on a gut full of water.

2. Potentially add in salts and carbohydrates to your water to aid in replenishing those sources (i.e. Powerade).

3. Specific rates of water intake vary between athletes and sports, so an individual approach is recommended.

4. Avoid a 2% loss in body weight as this causes significant performance decreases.

Post Training or Competing So, you have made it through the event. You have made sure to keep hydrated before and during the game, but it is likely you still need to replace some fluid stores in your body. The guidelines say to replenish 150% of the body weight you lost over the course of the activity, but this does not mean to chug it all in one go, absolutely not. That will cause a large blood pressure spike and cause greater dehydration in the long term. To retain as much of that water as possible, try and consume a meal with the fluid intake, which will also give other vital nutritional components such as carbohydrates, protein and salts.


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