Water is the most abundant molecule in the human body, accounting for ~60-70% of most athletes’ body mass. It is the nutrient that is lost and consumed in the largest amount each day and virtually every function or process that takes place in our body requires water. If you are not adequately hydrated, your body cannot perform at its highest level. Endurance exercise in particular places a high demand on the body’s hydration levels, as sweat rates are increased for prolonged periods of time.
A simple way to determine how hydrated you are on a day to day basis is by monitoring your urine. Colour, volume and smell are all good indicators of hydration status; dark colour, small amounts and strong smells can all signal dehydration. Weighing yourself before and after an exercise session is another great way of assessing how much fluid you typically lose from sweat during exercise.
Dehydration
Dehydration increases your chances of underperforming through various cardio strains and thermal strains of heat illness. In fact, as little as a 2% loss of water in your body can result in a significant performance decrease. Typical sweat losses during endurance training or competition are in the range of 1-2 L/h but can reach 3-4 L/h in some well-trained populations (Baker et al., 2016). The rate at which you sweat depends on many factors including exercise intensity, duration of activity, environmental conditions, cooling ability and individual characteristics such as body weight, heat acclimatization and more. Early signs of dehydration can include thirst, flushed skin and increased perception of effort or feeling dizzy or disoriented.
The effects of dehydration include:
- Reduced blood volume
- Reduced sweat production (thermoregulation)
- Reduced cognitive function and concentration
- Increase in overall body temperature
- Increased time to fatigue
- Increased rate of muscle glycogen use
It’s important to make up for these sweat losses during training through consistent and adequate hydration.
Electrolytes
Electrolyte status is another key factor in determining hydration status. Electrolytes are essential minerals (including sodium, potassium, magnesium and calcium) that the body needs to stay hydrated. They also support important processes within the body including muscle contraction, blood pressure and nerve signaling. Electrolytes can be consumed before, during and after exercise and are available in supplement form or through real foods and fluids such as coconut water, milk and various fruits.
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Hydration Guidelines
- Be proactive. Always aim to start exercise in a hydrated state.
- Use urine colour as a simple method of monitoring hydration status day to day.
- Aim to consume 500ml or 6-8 ml per kg body weight in the 2 hours before your exercise begins.
- Aim to replace 1.5 litres of fluid for every 1kg of weight lost during exercise.
- Add electrolytes to your rehydration drinks in warm weather or for intense sessions.
- Hydrate using a variety of fluids.
- Factor in your environment. Weather conditions (humidity, hot, cold) can influence your needs.
- Baker, L.B., K.A. Barnes, M.L. Anderson, D.H. Passe, and J.R. Stofan (2016). Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. J. Sports Sci. 34:358-368.
SUN RUN HOT TIP
Stay hydrated and have fun!
Photograph: © Unsplash / Nigel Msipa
