Wednesday, November 16, 2011

Match Fatigue: The Brain or Muscle?

Sourced from The Science of Soccer,

There is little doubt that a 90-minute soccer match takes its toll in the players. As the match progresses, fatigue sets in and performance suffers. The number of sprints and amount of running declines and technical abilities may fall off. 

Performance during any voluntary effort, be it running, sprinting or a strength test involves two physiological components. The first is the central nervous system (that is, the brain) and what is called “central drive” (or loosely described as effort). The second is the muscle’s intrinsic ability to produce force. If either central drive or muscle function declines, then overall performance declines.

“Central fatigue” is often thought of as psychological and the player simply giving up. However, central fatigue can have a physiological origin and factors beyond the players control can affect psychological effort. Researchers at the University of Milan found that match play induces significant central fatigue that persists into the next day. Their findings have important implications for diet strategies designed to prevent central fatigue and insure that performance does not suffer.

Twenty-two young professional players were used in the study. All were members of an Italian Serie A team (average age, 19). The players initially underwent a series of field and laboratory tests of performance. Several days later, they played a 90-minute match (arranged specifically for this study). Within 45 minutes of the match, the players repeated the field and laboratory tests. This was done again over the next two days (24 and 48 hours post - match)

The investigators used a combination of field and laboratory tests in order to evaluate and distinguish between central and muscle fatigue. As for field tests, they measured performance during the Loughborough Short Passing Test (LSPT) and a shuttle sprint test. Ratings of muscle soreness were also recorded.

In the laboratory, they measured quadriceps strength during a knee extension trial. To evaluate each player’s central drive or effort, the investigators also used the techniques of electromyography (EMG) and electrical stimulation of the quadriceps muscles.

The EMG is a measure of the electrical activity of the muscle. It measures the ability of the central nervous system to activate the muscle – central drive. If during a maximal voluntary contraction, both strength and EMG signals decline, researchers conclude that the subject’s central drive is reduced and he is experiencing central fatigue. On the other hand, if force declines but the EMG remains maximal, central drive is normal and the subject is experiencing muscle fatigue. Thus, the players performed a voluntary knee extension trial while both strength and EMG was recorded

Electrical stimulation is used to bypass central nervous system and artificially activate the muscle. It gives researchers an indication of how the muscle performs independent of the subject’s effort. Electrodes were placed over the quadriceps muscles and they were stimulated during the voluntary contraction. If force during a voluntary effort is increased by stimulation, researchers conclude that the central nervous system is not fully activating the muscle and the player is experiencing central fatigue.

The results of the investigation showed that after the match, players experienced a decline in sprint performance as well as an increase in muscle soreness. This persisted up to 24 hours after the match. By 48 hours post-match, performance had returned to normal and soreness had subsided. LSPT (short passing) performance was not affected at any time point.

In the laboratory, the researchers found that voluntary quadriceps strength was reduced immediately and 24 hours after the match. EMG signals recorded during these voluntary efforts were also reduced post-match. However forces during electrically stimulated contractions were not noticeably affected. For example, after the match, voluntary strength was reduced by 11% and EMG was diminished by 12%. However, electrically stimulated force was unchanged from pre-match values. When the central nervous system is bypassed by stimulation, strength is near normal. This suggests that during a voluntary effort (such as sprinting), central drive is reduced which leads to a decline in performance.

These findings suggest that players experience significant central fatigue during and after a soccer match. This decline in central drive likely diminishes strength and sprint performance. It appears that the muscle is not markedly fatigued but the central nervous system’s ability to fully activate it is compromised.

What causes central fatigue? The most obvious explanation is a lack of conscious effort. That is, simply “giving up”. Conscious effort can be affected by factors such as pain and the players did report increased pain after the match. So, it is possible that the discomfort felt during a maximal effort caused them to “back off” a bit. However, this study used a group of high-level professional players. One would assume that they are very competitive and used to playing with muscle soreness and giving a maximal effort despite the discomfort.

A second explanation has a more physiological basis. Researchers have shown that soccer players experience significant declines in muscle glycogen (energy stores) over the course of a 90-minute match. In some cases, this causes a decline in blood glucose (blood sugar) and these players experience hypoglycemia. Blood glucose is the primary fuel used by the brain for energy. Thus, a drop in blood glucose can lead to a number of psychological changes including feelings of tiredness, lethargy, and irritability. Motor skills can also suffer. All of these work together to cause central fatigue. Despite the player’s desire to perform, the effects of central fatigue on muscle function can dramatically hinder performance.

How can central fatigue be avoided? An important strategy is diet. Eating a proper diet, one that is high in carbohydrates and low in fat will maximize pre-match muscle glycogen levels. More muscle glycogen at the start of the match lessens the possibility of glycogen depletion and hypoglycemia. Also, by eating a proper recovery diet, glycogen stores can be quickly replenished so that players can recovery in time for the next day’s training or match. Thus, central fatigue that may occur during a match can be avoided by eating the right foods at the right time.

Back to the title of this post. Fatigue during any activity is complex and involves more than one cause, including both the brain and muscle. What this study emphasizes is the important role of the brain and central nervous system. Diet and central fatigue are an often overlooked aspect of training, especially by younger players. More detailed information about critical link between diet, fatigue and match performance can be found on the Science of Soccer Online as well as in our book, “The SCIENCE Behind Soccer Nutrition”.


Rampinini E, Bosio A, Ferraresi I, Petruolo A, Morelli A, Sassi A (2011) Match-related fatigue in soccer players. Medicine and Science in Sports and Exercise. DOI: 10:1249/MSS.0b013e31821e9c5c.

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