Hydration & Energy
Drink !
Average water losses when playing a sport are from 1 to 3 litres/hour (up to 10 litres/hour in extreme cases).
Dehydration is a cause of reduced performance once 1 to 2 % of body weight is lost (0.7 l to 1.4 l for a person weighing 70 kg); at this stage, the reduction in muscular efficiency has already reached 10%!
Beyond 4%, you can experience great tiredness, heavy legs, breathlessness, confusion, ...
And beyond 6-8% the risk of accidents arising becomes significant (exercise heatstroke...).
You must always hydrate yourself before you start to feel thirsty, because this only appears once you are already dehydrated. Train yourself to hydrate yourself well, to anticipate thirst and dehydration !
To avoid dehydration, you have to take account of heat losses that will vary according to weather conditions (temperature, wind), the level of training and clothing.
Let's note that the state of fatigue and stress are factors conducive to dehydration.
Remember that being perfectly hydrated before exercise is essential to good performance and prevention of muscular accidents during exercise.
A hypertonic liquid (too rich in energy), such as fruit juice or a drink with too much sugar, does not provide good hydration. On the other hand, an isotonic drink has osmotic properties allowing it to ensure good hydration.
Head for energy !
Physical exercise can cause an increase in energy expenditure of 500 to 1000 kcal/hour or even more, depending on the weather conditions (cold), intensity of the exercise, etc.
Energy systems in the muscle
The "substrate" used by the muscle is called adenosine triphosphate (ATP). Thanks to this substance, the muscle converts chemical energy into mechanical energy with the production of heat (which is why we need temperature regulation with the production of sweat and loss of water and mineral salts).
ATP is present at a very low concentration in the muscle and so can only sustain the first 3 seconds of exertion. These very limited reserves require continuous re-synthesis of ATP.
There are 3 systems of synthesis :
Alactic anaerobic system : synthesis of ATP from creatine phosphate present in the muscles, which enables the energy supply to be prolonged until the 15th second of exertion. An especially useful system for short intense exertions (sprint, weightlifting, jumping, throwing) that takes place without oxygen.
Lactic anaerobic system : synthesis of ATP by the use of carbohydrates, without needing oxygen. Method that enables exertion to continue for 2 to 4 minutes, but which is limited by the production of lactic acid, leading to acidosis of the muscle fibres
Aerobic system : synthesis of ATP requiring the presence of oxygen and which enables mixed use of carbohydrates and fatty acids. A theoretically unlimited method because lipid reserves are inexhaustible. This is the metabolic system best suited to long lasting exercise..
When the body is at rest, only the aerobic system operates. 1/3 of the energy is provided by carbohydrates and 2/3 by fats.
During exercise, the demands on the different ATP generating systems depend on 2 factors: the intensity and duration of the exercise. Between very short and intense exertions (strictly anaerobic) and long lasting exercise of moderate intensity (strictly aerobic), most exercises mobilises all three energy systems.
Aerobic endurance training (when you can sustain a normal conversation without panting during exercise) increases the use of fats, which enables the naturally low levels of glycogen reserves to be saved.