Fatigue should be interpreted as the inability of the muscle or joint agency to maintain the same intensity of effort during physical activity. It is a body's defense system to avoid possible negative consequences caused by an excessive practice. This is when our bodies make it necessary to stop or at least reducing the amount of effort or strength of the activity we are doing

Fatigue appears to cause a marked disproportion between the amount of exercise and the possibilities of doing, hence the importance of evaluation of an activity before undertaken. We need to assess possible factors in the face to avoid the appearance of fatigue. To do this it is necessary and important to know the duration of the activity to be performed, our physical condition ... ahead of dosing the effort and make it be "in crescendo" and not vice versa, in order to achieve progress. Types of fatigue are many and varied, however we will focus on those that may be of concern to us directly, in order to learn a little more that happens to us when we feel tired and why.

Fatigue Psychic Source: Comes ing a situation of intellectual stress and long lasting. Is important to take this into account, since the physical performance is much smaller when head is in "another place." The best remedy is rest and sleep.

Fatigue caused directly by muscle activity: It develops excessive levels of intensity, either by the amount, duration or speed of execution. Depending on the duration of the effort and the physical conditions of each can arise four different types of fatigue, may be given alone or more than one at a time.

LOCAL FATIGUE affects a particular area and defined muscle, which corresponds to the area involved in the realization of a particular type of specific exercises. For example, in those exercises that are carried out at high power stress. The level of impairment to the body of this type of fatigue is small or nonexistent, so it only affects the muscles involved in the activity

CAUSES: There are many possible causes, however we focus on two main, they are:

Insufficient oxygen supply: The case is easily muscle movements based on intense isometric contractions, this situation occurs in working conditions in which oxygen demand are greatly increased. If the body does not get what they need for oxygen is forced to use muscle energy reserves because of difficulties from the blood supply

Depletion ENERGY: The energy potential of the muscle fiber is limited and even more if we have the conditions of lack of oxygen to the muscle to bear on this kind of fatigue.

If the activity is very large we can only do it for about 8 to 10 seconds without showing fatigue. If the activity is less we can do it for 10 or 20 minutes (the difference is great). Of course, always influence the physical conditions of each side to delay the onset of fatigue.

TRAINING LEVEL: According to increase our energy reserves can reduce the possibility of fatigue (within the time limits mentioned above)

COMPOSITION CHARACTERISTICS OF MUSCULAR: Well not everyone has the same amount of muscle fibers. There fatigable fibers more easily than others, but their number is a function of metabolism of each individual.

SYMPTOMS: Decreased force of contraction, especially clear with regard to the maximum force attainable and amplitude of contraction.

Increased relaxation time: Modification of muscle capacity, reducing speed pacing and execution, as well as increased response time to external stimuli. Increased risk of injury, muscle pain, contractions and discomfort after exercise. Naturally, these risks are always higher in the poorly or untrained people.

Chronic fatigue (overtraining): Following intense sports practice and continuously for long periods, the condition may arise from chronic fatigue could be said to be pathological, that is, to worsen and persist, you can develop a true pathological condition.

SYMPTOMS: They are very diverse and varied, including highlights:

Decreased force of muscle contraction
Frequent accidents and muscle and joint injuries
Increased resting heart rate and exercise
Increased resting ventilation
Decrease in maximal voluntary ventilation
Increased ventilation in exercise of equal power
Menstrual irregularities and fertilization capacity
Neurosis and personality changes
Insomnia
Loss of appetite
Impaired mental performance
Feeling of exhaustion and fatigue
Decreased dexterity and coordination ability
Reaction time increases
Decreased performance.

ACUTE FATIGUE: It takes place in short periods of time since the beginning of the effort or exercise program

GENERAL FATIGUE: It is one in which the demonstrations reach throughout the body. This pattern is typical of those physical exercises involving major muscle mass, but not only affects the feature set, muscular, but also all organic functions, since the body functional systems also participate in an active and intense

CAUSES: general fatigue is usually the union of several important causes with relatively variable and operating at various levels in the body.

MUSCULAR COMPONENT: In this type of fatigue, muscle mass is important requested a progressive exhaustion of those fuels that are able to be used by the muscle fibers. Since this is predominantly aerobic exercise (muscles receive oxygen while working, because the intensity is not excessive), and the contractions are alodinámicas (those in which the forces of muscle contraction varies depending on the different angles of joint movement) must be regarded as the depletion of glycogen reserves themselves affected muscle fibers, both organic as glycogen general as lipids and proteins.

Anyway, are rare qualifying as intense exercise in which aerobic exercise is by nature pure, without a more or less important anaerobic metabolism (the muscles do not receive oxygen while working). Therefore, especially in specific areas requested, with increasing duration of effort, there is a buildup of lactic acid, which in these conditions of metabolic functional overload are problematic, which means that more or less affect degree the opportunity to continue with the effort

NEUROLOGICAL COMPONENT: Also called "central fatigue", usually has a great importance in those exercises of long duration. Glucose uptake at the level of active muscle is overstated and that stocks are depleted. The neuron depends on glucose for fuel exclusively, so that before such activities were forced to cease or reduce their activities in part, limiting or reducing the degree of movement.

Under these conditions the accuracy of the movement will be less. Increases energy consumption required for the execution of movements and reduces profitability. This leads to the condition of fatigue.

CARDIOVASCULAR COMPONENT: It is sometimes the only responsible for the condition of fatigue. You may be unable to continue his work at levels much higher than usual, which can not be assured to continue their level of cardiac output (amount of blood ejected from the heart per minute), for long periods (the heart, as other muscles, also fatigue). When this happens is unable to respond successfully to the needs of increased blood flow and is unable to sustain any longer the levels maintained until then. The result is the impossibility to continue the same level of effort, or fatigue.

Thermoregulator COMPONENT: garner the inability to mitigate the excess heat produced during intense physical activity, especially if this is done in a worse climate. In other words, is not the same, for example at a gym full of people, where it is hot and that does not facilitate natural ventilation of the body, to train in a park, where the body can breathe while ventilated air pure, whatever benefits the body cooling. Increased body heat, plus it can be a physical cause for the arrest of the effort (what is commonly known "heat stroke"), often act more indirectly. How? very simple: The cardiovascular and respiratory system are increased its real workload of the body must endure. The cardiovascular system must also carry a greater number of blood to the circulation of the skin, which makes you see the condition of dehydration. It then begins to appear wheezing, which increases work of breathing and also introduces a subjective factor unpleasant sensation of breathlessness, which also ends up causing the situation of fatigue.

SYMPTOMS: While there may be many here reflect only those most characteristic

Depletion of body stores.
Increased resting heart rate and stress
Heart rhythm disturbances
Sensation of shortness of breath
Wheezing
Decreased energy efficiency
Decreased reaction time
Decreased level of reserves for inspiration
Increased risk of "heat stroke"
Decreased effort or detention