Some fitness enthusiasts are experiencing neural fatigue, which is a type of fatigue that is more difficult to recover from.

In exercise - related fatigue, neural fatigue is often overlooked. Retired athlete Harris recalled his days on the sports team, when neural fatigue was a major factor affecting the quality of training.

"For example, when in good condition, one might be able to easily bench - press 100 kg, but a few days later, it could be very strenuous or even impossible. Although there is enough training interval for the muscles to recover (more than 48 hours), there is just no energy and one can't exert their strength."

Compared with the well - known peripheral fatigue such as glycogen depletion, lactic acid accumulation, and electrolyte loss, neural fatigue is more unfamiliar to the public. However, this doesn't mean that neural fatigue is rare, especially after maximum - weight exhaustive training and long - term aerobic exercise.

According to the "protective inhibition theory", neural fatigue stems from the protective inhibition of the cerebral cortex, which in turn affects the ability of motor neurons to recruit muscles.

From a physiological and biochemical perspective, during exercise, the ATP content in the cerebral cortex neurons decreases, the ADP content increases, the blood sugar level drops, the levels of γ - aminobutyric acid and 5 - hydroxytryptamine in the brainstem and hypothalamus rise, and the ammonia content in the brain increases, causing fatigue symptoms such as tiredness, loss of appetite, and sleep disorders.

As a long - term and systematic lifestyle, fitness is not just about daily training; scientific recovery should also be a part of it.

Some fitness enthusiasts' fatigue comes from neural fatigue.

At the 5th International Conference on Sports Biochemistry in 1982, exercise - induced fatigue was defined as "the physiological process of the body cannot maintain its function at a specific level or cannot maintain the预定 exercise intensity".

With the continuous in - depth scientific research and the improvement of training systems, several representative theories have emerged regarding the causes and mechanisms of exercise - induced fatigue.

The more well - known ones include the "exhaustion theory", the "blockage theory", and the "internal environment stability imbalance theory". In addition, the "protective inhibition theory" proposed by the Pavlov school explains the occurrence of neural fatigue.

According to this theory, neural fatigue (central fatigue) is due to the protective inhibition generated in the cerebral cortex. During exercise, a large number of nerve impulses are generated in the relevant areas of the cerebral cortex, making it excited for a long time and consuming more energy. To avoid further consumption of energy - supplying substances, an inhibitory process is generated to protect the cerebral cortex.

Under the effect of the protective inhibition of the cerebral cortex, the input to motor neurons decreases, making it difficult to recruit muscles to the maximum extent.

Harris said that neural fatigue is not psychological "laziness" or "resistance to training", but a common physiological state.

"Although sometimes neural fatigue can be improved by extra rest, one also has to consider that their training plan will be disrupted and their psychological state will be affected accordingly. So, for fitness enthusiasts with periodic training or even competitive needs, neural fatigue needs to be taken seriously."

Blues music gives people a feeling of laziness and even "listlessness". Haruki Murakami used this analogy to describe the low mood and melancholy after running. However, regarding the reasons, Murakami gave more literary and spiritual answers.

"Over the years, I've run too much and for too long. Maybe it's because I'm approaching 50 and my physical strength has hit the unavoidable wall of age. Or perhaps I've unknowingly entered male menopause and am experiencing the mental downturn it brings."

Neural fatigue, a more difficult - to - recover fatigue.

In 1971, Yakovlev found that after mice swam for 10 hours and suffered severe fatigue, the content of central inhibitory neurotransmitter (γ - aminobutyric acid) in the cerebral cortex increased significantly.

In addition, factors such as a decrease in blood sugar level, hypoxia, a decrease in the pH value of the internal environment, electrolyte loss, and an increase in body fluid osmotic pressure will also cause the working ability of motor neurons to decline, thereby promoting the occurrence of neural fatigue.

Different from peripheral fatigue caused by the exhaustion of energy - supplying substances such as phosphocreatine and glycogen after exercise and the accumulation of metabolic products in muscles, neural fatigue is more difficult to recover from.

Statistics show that neural fatigue occurs more frequently in maximum - intensity anaerobic exercise and long - term aerobic exercise. Sports that require high concentration, such as shooting, table tennis, and yoga, are also prone to cause neural fatigue. At the same time, neural fatigue will gradually accumulate during multiple training sessions.

"Asia's flying man" Su Bingtian ran 9.83 seconds in the men's 100 - meter semi - final of the Tokyo Olympics. In a subsequent program interview, he analyzed his weaknesses in the competition, saying that "the neuromuscular fatigue caused by breaking the limit in the semi - final takes at least 12 hours to fully recover under the best existing legal scientific and technological conditions".

However, there was only a 2 - hour interval between the semi - final and the final. Coupled with the influence of other athletes' false starts in the final, "God Su" had a starting reaction time of 0.167 seconds in the final, which was the slowest among all the athletes, and he finally ranked sixth with a time of 9.98 seconds.

In exercise - induced fatigue, peripheral fatigue and neural fatigue are collectively referred to as physical fatigue. In addition, psychological fatigue is gradually being taken seriously.

In 2019, a research team from the University of Queensland in Australia surveyed 17 athletes and 15 relevant practitioners from elite sports organizations to explore their understanding of psychological fatigue in competitive sports [1].

Both athletes and relevant practitioners believe that psychological fatigue will have a negative impact on sports performance, manifested as a decrease in training motivation and enthusiasm, an increase in emotional and withdrawn behaviors, a change in attention, and a decrease in discipline.

The causes of psychological fatigue include the use of social media, study, training, repetitive tasks, over - analysis, thinking about sports problems, and an unstable environment. Training experience and individual differences also affect the susceptibility and resistance to mental fatigue.

Currently, there is no consensus internationally on the causes, nature definition, detection methods, and recovery means of psychological fatigue. There are few domestic studies on the role of sports psychology in training practice, and there is also a lack of localized coping methods [2].

Scientific recovery is also a part of fitness.

Regarding the prevention and alleviation of neural fatigue, Harris suggests changing the training method, such as changing from heavy - weight exhaustive training to light - weight muscle endurance training, or from equipment training to bodyweight training.

"We also adjust the training actions for the same body part every once in a while. For example, when training the back, one can first do pull - ups and barbell rows, and then change to high - pulley cable rows and barbell deadlifts after a period of time."

In addition to a scientific and systematic training cycle plan, recovery means such as sufficient sleep and a reasonable diet are also essential for fitness enthusiasts.

A 2017 review summarized the roles of 5 - hydroxytryptamine and dopamine in exercise - induced fatigue: during exercise, the level of 5 - hydroxytryptamine in the cerebral cortex rises and the level of dopamine decreases. The interaction between the two neurotransmitters jointly regulates the development of neural fatigue [3].

In neuroscience, there is a special diet rich in dopamine and low in blood sugar, which helps the brain produce more dopamine. It is also known as the "detox diet" and is often used to help alcoholics and drug addicts in their withdrawal and rehabilitation.

In the "detox diet", one can reduce refined carbohydrates, added sugars, and low - nutritional - value foods (such as chips, biscuits, chips, cakes, etc.) and increase: High - quality protein: eggs, cheese, yogurt, tofu, lean meat, poultry, and sea fish; Low - sugar fruits: all fruits (except bananas and melons); Vegetables: all vegetables (except white potatoes and corn); Whole - grain foods: whole - wheat bread and pasta, spelt, barley, buckwheat, farro, quinoa, etc.

High - quality sleep for 7 - 9 hours after exercise can not only promote the secretion of anabolic hormones but also help improve neural fatigue.

A study by a research team from Boston University published in the international top - tier journal "Science" in 2019 found that in the sleep state, the brain will turn on the "automatic cleaning" mode. The blood and cerebrospinal fluid show a slow cyclical change of ebb and flow. When the blood flow decreases, the cerebrospinal fluid flow increases to clean the metabolic products in the brain [4].

In addition, psychological methods such as psychological counseling, self - suggestion, and meditation have been scientifically proven to be able to reduce the tension of the neuromuscular system and relieve the protective inhibition of the cerebral cortex, and are gradually being taken seriously.