Research Progress Of Sports Fatigue Mechanism And Food-borne Anti-fatigue Active Ingredients

ABSTRACT: Sports fatigue is a temporary decrease in the body’s work capacity caused by exercise itself, which is manifested as a physiological phenomenon that can be recovered after proper time of rest and adjustment. It is also the result of the protective inhibition mechanism of the cerebral cortex. Excessive fatigue can easily induce sports injuries and directly affect the normal movement of the human body. Therefore, how to effectively prevent the occurrence of exercise-induced fatigue and fast recovery has become the key direction of current research. This paper summarized the main theories on the mechanism of exercise fatigue in recent years: energy consumption, accumulation of metabolites, protective inhibition, calcium ion metabolism disorders, etc.. It also summarized the effective ingredients of food-borne anti-exercise fatigue and their mechanism of action, and proposed that theanti-fatigue products compounded with a variety of biologically active peptides had a wide range of applications according to the application of multiple active ingredients in the research and development of anti-fatigue products, in order to provide theoretical guidance for the development of more safe, green and effective anti-fatigue products.

KEY WORDS: exercise fatigue; fatigue resistance; foodborne; dietary bioactive components

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Introduction

The concept of exercise fatigue has been proposed for nearly 200 years. It first started in 1880. Mosso first studied the changes in the working ability of the flexor muscles [1]. Since then, many famous scholars have adopted different methods from various perspectives Exercise-induced fatigue has been extensively studied and various definitions have been proposed. Until 1982, the Fifth International Sports Biochemistry Conference held in Boston, USA unified the definition of fatigue: exercise-induced fatigue is a physiological phenomenon that occurs when the human body’s mental and physical activities continue to a certain stage. Its function is at a specific level or it cannot maintain the predetermined exercise intensity[2], and the intensity of exercise training determines the degree of exercise fatigue, and appropriate intensity of exercise fatigue can promote the recovery of the human body through reasonable recovery methods.

The level of skill continues to improve, and excessive fatigue is not only detrimental to the improvement of sports performance, but may also cause sports injuries. As for its physiological production mechanism, it is mainly summarized as follows: the theory of energy material consumption, the theory of accumulation and blockage of metabolites, and the theory of protective inhibition[3‒5].

In recent years, scholars at home and abroad have conducted a lot of research on anti-fatigue active substances in animals and plants, and found that some natural active ingredients such as polypeptides, amino acids, polysaccharides, vitamins, and polyphenols have certain anti-exercise fatigue effects, and are widely present in food. source animals and plants. This article focuses on the review of the mechanism of exercise fatigue, food-derived active ingredients with potential anti-fatigue effects and their applications, in order to provide reference for the selection of safe and effective anti-fatigue active ingredients and the development of new compound anti-fatigue products.

1 Physiological mechanism of exercise fatigue

1.1 The theory of energy and matter depletion

Adenosine triphosphate (ATP) is the direct energy substance in various life activities of the human body, and in addition, nutrients such as carbohydrates, fats, and proteins provide energy indirectly for body movements. During exercise, the phosphagen system, lactic acid energy system, and aerobic oxidation system provide energy for life activities. When the energy supply is sufficient, the muscle tissue works normally, thus completing the exercise process;

When the supply of energy substances is in short supply, the energy produced in the athlete's body cannot maintain the exercise demand, the muscle function is impaired, and the scheduled intensity work cannot be completed, resulting in a sense of fatigue.

Studies have found that the duration and intensity of body exercise affect the generation of exercise fatigue by affecting the consumption rate of energy substances: In short-term, high-intensity exercise, the ATP-CP system provides the main energy, and high-energy phosphoric acid such as ATP and phosphocreatine in the body When fatigue occurs, the phosphocreatine content in the muscle drops to 20% of the pre-exercise level[6]. During long-term, low-intensity exercise, the aerobic oxidation system provides the main energy, and glycogen serves as the energy storage Substances are decomposed to supply exercise consumption and maintain blood sugar balance. Long-term exercise will consume a large amount of glycogen, resulting in exercise-induced fatigue. Animal experiments found that [5], when the dog exercised to fatigue, the blood sugar level decreased, and the injection of epinephrine increased the sugar utilization rate of the body to the muscle tissue, which increased the blood sugar concentration, and the dog's exercise ability was obviously restored. In addition, when a large amount of fat is mobilized, a large amount of free fatty acids will be produced, and the accumulation of plasma free fatty acids will promote the increase of free tryptophan. Excessive tryptophan entering the brain will cause the level of serotonin to rise, thereby inhibiting the working ability of the brain. Strengthen the central fatigue [7]. Under different exercise intensities, the body consumes energy substances in different sequences, and targeted energy supplementation can relieve fatigue.

1.2 Metabolite accumulation theory

Compared with the resting state, athletes consume more energy substances during high-intensity exercise, and at the same time produce more metabolites (lactic acid, NH4+, H+, etc.) [8‒9]. If these metabolites cannot be removed in time, they will It will block the normal substance metabolism, lead to the decline of muscle tissue motor function, and produce exercise-induced fatigue. During high-intensity exercise, athletes mainly supply energy through the lactic acid energy system. Glycogen (glucose) in the body decomposes to produce lactic acid in anoxic conditions. With the increase of exercise intensity, the lactic acid content in the body continues to accumulate. 40 mmol/kg wet weight, blood lactic acid up to 18 mmol/L[10], lactic acid dissociation produces H+, lowers the pH value of the internal environment, inhibits the activity of phosphorylase and phosphofructokinase, thereby inhibiting the energy supply of the lactic acid energy system, resulting in Insufficient ATP supply leads to fatigue[11]; in addition, brain cells are very sensitive to changes in blood pH, and a drop in blood pH can cause a decrease in the working ability of brain cells[12‒13].

SHANELY et al. [14] confirmed that the higher the lactic acid content, the more obvious the decline in the body's motor function, and the longer the recovery period from fatigue. Muscle contraction during human exercise can also produce NH4+ (AMP is catalyzed by deaminase). When the ATP in the body is consumed in large quantities, the ammonia content in the body increases[15]. The increase in ammonia content can promote glycolysis and produce lactic acid and H+, resulting in The activity of some enzymes is reduced or even inactivated, and the combined effect of lactic acid and ammonia reduces body function and causes fatigue[16]. Studies have shown [17] that the generation of NH4+ in the body is positively correlated with exercise intensity. During exercise, due to the enhanced amino acid metabolism and the increase in the concentration of adenosine diphosphate in the muscle, the blood ammonia concentration rises and the activity of citrate dehydrogenase is inhibited. It affects the body's energy metabolism and exercise balance, and even causes muscle spasms [18]. Studies by FWENSTROM, BANISTER et al. [19‒20] have confirmed that elevated blood ammonia levels can enter brain tissue, have neurotoxic effects on brain cells, disrupt the balance of glutamic acid and γ-aminobutyric acid, and lead to central fatigue.

All in all, timely removal of metabolites and stabilization of lactic acid and NH4+ levels in the body are of great significance for alleviating fatigue.

1.3 The theory of central nervous system protective inhibition

According to the Pavlovian school of view, protective inhibition produced by the brain triggers exercise fatigue. During high-intensity mental or physical exercise, a large number of impulses stimulate the corresponding neurons in the cerebral cortex, resulting in long-term excitement. In order to avoid excessive consumption of energy substances such as glycogen, when it reaches a certain level, the cerebral cortex will produce protective inhibition. , produce a sense of fatigue to remind the body to stop exercising[21], during long-term high-intensity exercise, the content of branched-chain amino acids in plasma will decrease, making aromatic amino acid (aromatic amino acid, AAA)/branched-chain amino acid (branched-chain amino acid, BCAA) value increases, in addition, the content of γ-aminobutyric acid in the brain increases during fatigue, which will also lead to inhibition of the cerebral cortex[22].

1.4 Ca2+ metabolism disorder theory

Ca2+ is an important regulatory factor in intracellular nerve-muscle signal transduction and exercise-induced fatigue caused by aerobic exercise[23]. Recent studies have found that high concentrations of Ca2+ in the cytoplasm for a long time can induce the apoptosis of normal muscle cells, and the imbalance of calcium homeostasis in muscle cells will eventually lead to muscle fatigue and injury [24]. In addition, exercise causes an increase in the concentration of Ca2+ in the cytoplasm, and mitochondria have the function of buffering and regulating the concentration of Ca2+ in the cytoplasm. When fatigue occurs, lipid peroxidation in the cell membrane system is triggered, and the permeability of the mitochondrial membrane to Ca2+ increases, and a large amount of Ca2+ enters the mitochondria. When calcium abnormality occurs, excessive calcium ion accumulation will inhibit the oxidative phosphorylation process of mitochondria, decouple oxidative phosphorylation, reduce ATP production, and then cause cellular calcium ion metabolism disorder, forming a vicious circle and causing different

degree of muscle fatigue and injury [25].

2 Research on food-derived anti-fatigue active ingredients

There are various food-derived anti-fatigue ingredients found in current research, but the overall research is still in a preliminary state. Methods to evaluate fatigue include endurance test and biochemical index detection. For evaluating exercise tolerance, the mouse exhaustive swimming test is commonly used. According to the judgment standard in the "Implementation Manual of Health Food Inspection and Evaluation Technical Specifications": "The weight-bearing swimming test result is positive, and any two of the three indicators of blood lactic acid, serum urea nitrogen, and liver glycogen are positive, and the test sample can be judged as positive." It has the function of relieving physical fatigue” [26]. In recent years, scholars have discovered [18] that some natural active ingredients in food: peptides, amino acids, polysaccharides, vitamins, carotene, glycosides, etc., all have anti-fatigue effects.

2.1 Bioactive peptides

Food-derived bioactive peptides are mainly hydrolyzed products of protein by enzyme, acid or alkali, and directly extracted from natural animal and plant tissues with high content of active peptides. They have the characteristics of fast absorption, comprehensive absorption, and no energy consumption[27 ]. As shown in Table 1, aquatic products, insects, and mammals are the main sources of anti-fatigue bioactive peptides derived from animal foods, while soybeans, corn, and peanuts are the sources of bioactive peptides derived from plant foods.

The main source of anti-fatigue bioactive peptides, and different sources of bioactive peptides have different mechanisms of anti-exercise fatigue. Biological activity can reduce the swelling and expansion of skeletal muscle mitochondria and mitochondrial membrane permeability, and reduce blood urea nitrogen (BUN). ) content, increase liver glycogen, superoxide dismutase (superoxide dismutase, SOD), lactate dehydrogenase (lactate dehydrogenase, LDH) content to relieve exercise fatigue [28‒36].

2.2 Polysaccharides

Polysaccharides are a class of natural active biomacromolecules with immunomodulatory functions. In recent years, studies have found [37] that sugars are also effective in anti-fatigue. The polysaccharides extracted and isolated from plants have anti-inflammatory properties such as scavenging free radicals, inhibiting lipid peroxidation, and inhibiting linoleic acid oxidation. Fatigue effect.

In the study of Niu Jiamu et al. [38], male ICR mice were supplemented with 20 mg/kg Schisandra polysaccharide (SCP-A) solvent, and then carried out weight-bearing swimming, forelimb grip strength test and serum urea nitrogen (BUN), blood urea nitrogen (BUN), The determination of serum lactic acid (LA), malondialdehyde (MDA), and 8-OHdG levels further confirmed that SCP-A has significant anti-fatigue and anti-oxidation effects. In addition, as shown in Table 2, mushrooms, wolfberry, black fungus, and Dendrobium officinale are the main sources of food-derived anti-exercise fatigue polysaccharides, mainly through reducing

Blood lactic acid and reduce BUN level, improve liver glycogen and muscle glycogen reserve mechanism anti-fatigue [39‒44].

2.3 Amino acids

As the basic components of protein, amino acids can provide energy for the body during exercise. Supplementing amino acids can supplement the protein consumed by the body during high-intensity exercise to a certain extent, and plays an important role in alleviating fatigue. The study found[45] that after gavage of 40 mL ꞏkg-1BW Flammulina velutipes amino acid solution to male Kunming mice for 7 consecutive days, the content of liver glycogen in the mice increased significantly, the weight-bearing swimming time of the mice increased significantly, MDA, blood lactic acid and serum The content of urea nitrogen was significantly reduced. At the same time, morel amino acids, Agaricus blazei branched-chain amino acids, and Northeast wild hazel mushroom amino acids [46‒48] all showed high anti-fatigue effects in experiments. Taurine is a non-protein amino acid, which can promote the elimination of free radicals in the body and improve the body's anti-fatigue ability by blocking lipid peroxidation [49].

Branched-chain amino acids include isoleucine, leucine, and valine, which are three essential amino acids that the body cannot synthesize by itself and must be ingested from food protein. Branched-chain amino acids can reduce the level of free radicals in the body after exercise and increase the activity of antioxidant enzymes. At the same time, it is also conducive to the stability of calcium concentration in the body, can reduce the concentration of blood lactic acid after exercise, and has a certain effect on the recovery of fatigue after exercise. effect,

And can improve the body's exercise capacity [50]. In addition, supplementing a certain amount of branched-chain amino acids after exercise can also reduce the rate of tryptophan entering the brain, maintain the normal function of brain cells, and slow down the occurrence of central fatigue.

2.4 Polyphenols

Polyphenols are aromatic compounds containing polyhydroxyl groups, which are widely found in dark-colored vegetables, fruits, beans and other plant foods. In recent years, a large number of studies have found that polyphenols have anti-fatigue effects, and phenolic substances can generate stable semiquinone free radicals through the reaction of phenolic hydroxyl groups with free radicals, thereby terminating free chains.

Reaction, so that polyphenols have strong antioxidant and free radical scavenging ability. Chen Rong et al[52] administered different doses of Gorgon seed coat polyphenol saline solution (400, 200, 100 mg/kgꞏd-1) to healthy mice for 5 consecutive days, and carried out weight-bearing swimming and atmospheric hypoxia experiments 30 minutes after the last time. , the content of liver glycogen and muscle glycogen was measured 24 hours after the last occurrence, and it was found that liver glycogen and muscle glycogen reserves in fatigued mice increased, serum urea nitrogen levels decreased, and lactate dehydrogenase levels in serum and liver increased, confirming that Gorgon Seed coat polyphenols have anti-hypoxia and anti-fatigue effects.

Experiments conducted by the Physical Education Department of Xi’an University of Technology[53] found that after 30 days of intragastric administration of different doses of tea polyphenol extracts, compared with the control group, the activity of blood lactate dehydrogenase in rats after exercise increased, while the levels of blood lactic acid and urea nitrogen decreased , and the effect of 300 mg/kg dose was the most obvious. Liu Qi[54] was studying the optimal purification process of Acanthopanax polyphenols, prepared 50 mL of polyphenol adsorption solution with a concentration of 0.1 mg/mL and pH=4, and loaded the sample to 5 g AB at a flow rate of 2 mL/min. -8 resin for adsorption, using 70% ethanol solution with a volume of 100 mL, and eluted at a flow rate of 1 mL/min. This adsorption solution can significantly prolong the swimming exhaustion time of mice, thereby improving the anti-fatigue level. In addition, natural polyphenols such as tannic acid, anthocyanin, catechin, puerarin, tea polyphenols, rutin, curcumin, quercetin, and soybean isoflavones all have obvious anti-fatigue effects[55] .

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2.5 Anti-fatigue research of vitamin ingredients

Vitamins are essential nutrients for the growth and development of the body. They can only be ingested from food and cannot be synthesized by the body itself. They can be divided into water-soluble vitamins and fat-soluble vitamins. Studies have found that vitamins A, B, C, and E can effectively inhibit lipid oxidation in cells, and have strong antioxidant and free radical scavenging capabilities.

Vitamin A is essentially an unsaturated monohydric alcohol composed of β-angelinone ring and 2 molecules of 2-methylbutadiene. Zhou Xiufen[56] found that adding an appropriate amount of vitamin A can improve the vitamin storage level in rats to a certain extent. , and improve the body's antioxidant capacity. Ma Lu[57] found in the study that after adding 220 IU/kg BW vitamin A to dairy cow feed, superoxide dismutation in serum,

The activities of glutathione peroxidase, catalase, total antioxidant capacity and hydroxyl free radical inhibition are enhanced, and the antioxidant capacity of the body is improved.

Vitamin E is an important antioxidant. Taking vitamin E orally after heavy exercise training can inhibit the formation of oxygen free radicals in the body, improve the body's antioxidant capacity, and reduce the plasma endothelin content and serum nitric oxide content of rats. The endothelin/nitric oxide ratio decreased, indicating that vitamin E has a protective effect on the endothelial cells of rats trained with heavy exercise, and can improve the body's movement

Dynamic ability and anti-fatigue ability [58].

3 The role of food-derived anti-fatigue active ingredients in anti-fatigue foods

Application of research in recent years has found that there are various food-based active ingredients with anti-exercise fatigue effects, covering various nutrients necessary for life activities, but most anti-fatigue products are still in the preliminary exploration stage. As of July 2016, the data query results of the State Food and Drug Administration show that my country has approved and registered 751 imported health foods and 15 842 domestic health foods.

Among them, there are 2160 products with the function of relieving physical fatigue (including the original "anti-fatigue" function), accounting for 13.63% of the total number of health foods [59]. The anti-fatigue products in the market can be roughly divided into three categories: (1) The anti-fatigue health care products with high prices, such as American ginseng, maca, rhodiola rosea, and Cordyceps sinensis, etc. In the experimental research in the plateau area, the physical education students in the experimental group who took a Rhodiola anti-altitude exercise fatigue food were significantly better than the physical education students in the control group in terms of exercise time and exercise distance [60]; (2) It can be seen everywhere in the market, Inexpensive sports functional drinks, such as Red Bull, Gatorade, Jianlibao and other brands, these products mainly rely on timely supplementation of sugar and multivitamins consumed during exercise to relieve fatigue; (3) bioactive peptides as the main Raw materials, combined with other Chinese herbal medicines and a variety of amino acid compound anti-fatigue health products, such as Ganweile that has been developed on the market, the main active ingredients include polygonatum polysaccharides, corn oligopeptides, black tea polyphenols, amino acids, unsaturated fatty acids In the research, it can prolong the weight-bearing swimming time of mice, reduce the accumulation of metabolites, increase the storage of glycogen, and exert a good anti-fatigue effect.

4 Summary

To sum up, exercise fatigue is a complex physiological and biochemical process involving peripheral tissues and central nervous system. Aiming at the mechanism of exercise fatigue, by summarizing the research in recent years, mainstream theories such as the theory of energy substance depletion, the theory of metabolite accumulation, and the theory of protective inhibition have been formed, and the mechanism of fatigue has been elaborated in detail. Research on anti-fatigue active ingredients;

Polypeptides, proteins, and sugars can relieve fatigue by timely supplementing energy substances; polyphenols, vitamins, amino acids, etc. can achieve anti-fatigue effects by scavenging free radicals. In future research and development, it is expected to efficiently extract active ingredients from animals and plants, targeting For different degrees of different types of sports fatigue, a variety of anti-fatigue ingredients are compounded to produce green and efficient anti-sports fatigue products.