Training in hot conditions can have unfavourable effects on both health and performance. Physiological strain from excessive heat can cause symptoms such as fatigue, weakness, dizziness, confusion, and fainting. However, we are well adapted to perform in the heat as we have many built in mechanisms which help with heat loss. The most important of these is our sweat glands. Hot conditions cause both blood flow and sweat rate to increase which allows the body to cool. Over 2 litres of sweat can be lost per hour when exercising in the heat. If you are or become dehydrated during these type of conditions, it can greatly increase the strain on the body. Body water deficits that exceed just ∼2% of body mass impairs performance, especially those of a long duration.
Water can be described as one of the most underrated and neglected nutrients. It makes up over half of who we are, with the muscle in our bodies being about 75% water. A good hydration strategy can contribute significantly to optimal performance. Sweat losses need to be replaced during and after exercise. It should be remembered that as well as water, sweat contains electrolytes such as sodium which also needs to be replaced to maintain optimal body function and the perception of wellbeing. Electrolytes help with different body processes and if not replaced, this can lead to cardiovascular strain, increased glycogen use, altered metabolic and central nervous system function, and a greater rise in body temperature. Simply adding a dilute solution and pinch of salt to your water should help rehydrate you better as well as replace those lost electrolytes.
Some health care professionals recommended that you should drink to thirst and in most settings, with the general population, drinking when thirsty is appropriate. Our bodies regulate our thirst so that we take in more when we need it. However, it has been reported that this method of drinking can still result in water deficits when training in warm environments, especially among well trained individuals who are pushing themselves to the limit. Sometimes there is a lag time between losing fluid and being thirsty and unfortunately by the time performance suffers, it is already too late.
We get around 1 litre of water from food each day. On top of this you should take in around 2 litres (varies with height and weight) from drinking. When we are rested and in a well-fed state it is usually safe to assume we are hydrated as well. Although as mentioned above, if you are sweating, you will need more. For moderate to high intensity activity lasting under 1 hour you should try to consume an additional 0.5-1 litre of water during the activity. The same should be done once the workout is completed. Following training in the heat, rehydration is particularly important to optimize recovery. You should consider adding drinks such as chocolate milk to your hydration strategy as it has a carbohydrate‐to‐protein ratio of 4:1, as well as sodium, which helps promote recovery and protects against muscle loss.