In a 90-minute game, athletes spend about 70% of their time working at a low intensity, but they are required to perform repeated bouts of high-intensity efforts. Top players will cover 10-13km in a game, with about 150-250 briefly intense efforts. This intermittent work, places strain on the anaerobic system and is the main culprit in the fatigue that occurs during a game.


Here are some potential causes for excessive fatigue in football.


Depletion of muscle glycogen stores


Insufficient carbohydrate intake before and during training/competitions increases the risk of the depletion of muscles’ glycogen stores. Carbohydrates are a necessary source for high-intensity bouts of exercise.


Low blood glucose (hypoglycemia)


Low levels of blood glucose compromise your ability to exercise. Reduced blood glucose can result in slower reaction times and poor decision-making skills.




Sweating is your body’s way of cooling itself down. Fluid loss can cause dehydration, if an adequate amount of water is not taken. Dehydration can lead to impaired physical and mental performance.


Iron deficiency


Iron is responsible for carrying oxygen to the tissues from the lungs. If a player has an iron deficiency, they may suffer fatigue and impaired performance.


Low energy availability


Energy needs will vary daily, depending on the type, duration and intensity of training sessions. Everybody has different energy requirements, so there is no “one size fits all” approach to energy intake. It is important to ensure that you eat enough to balance the energy used in exercise.

Low energy availability is caused when you do not consume enough daily calories, to replace what you have spent through exercise. Energy deficiency can result in poor athletic performance, as your body competes to recover properly between training sessions, and starts to prioritise fuelling basic bodily functions rather than the working muscles. A prolonged period of energy deficiency (also known as RED-S) can lead to poor bone health, as your body struggles to find the energy to replace bone loss.