Sports Research Series: Muscle Fatigue
Background
Concept
Fatigue: In daily life, people may experience a decrease in work ability, which is called fatigue.
Sports fatigue: In 1982, the American Society of Sports Biochemistry officially defined "the inability of the body to maintain a specific level or intensity of exercise" as sports fatigue. (Decreased work ability - exhaustion)
Sports induced muscle fatigue: Sports induced muscle fatigue is defined as a physiological phenomenon in which the maximum voluntary contraction force or output power temporarily decreases when muscles contract due to exercise.
mechanism of occurrence
① Exhaustion theory
This theory holds that,In motionDuring the process, a large amount of energy substances (ATP, phosphocreatine, sugar, fat, etc.) are consumed in the body, resulting in energy shortage and a decrease in muscle working ability, which cannot complete the predetermined intensity of work, leading to fatigue.
② Blockage theory
This theory suggests that during exercise, the increased energy metabolism activity in the body leads to the production of certain metabolic products(Lactic acid, ketone bodies, ammonia, etc)Excessive accumulation that cannot be eliminated in a timely manner can lead to a decrease in the working ability of muscles and other tissues, resulting in exercise-induced fatigue.
③ Protective inhibition theory
During exercise, a large number of impulses stimulate the corresponding neurons in the cerebral cortex, causing them to remain excited for a long time and leading to increased consumption. When energy consumption reaches a certain level, an inhibitory process occurs to protect the cerebral cortex.
④ The theory of steady-state imbalance in the internal environment
This theory suggests that during high-intensity exercise, the body's metabolism significantly increases, leading to a decrease in blood pH, changes in plasma osmotic pressure and electrolyte concentration, causing changes in the internal environment of the body and ultimately leading to fatigue.
⑤ Mutation theory
This theory suggests that the three-dimensional spatial relationship of energy expenditure, decreased muscle strength, and loss of excitability during exercise triggers fatigue. Energy consumption, decreased muscle strength, and loss of excitability form a control chain, and any interruption or obstruction in any link can lead to fatigue.
⑥ Free radical damage theory
This theory holds that excessive production of free radicals in the body can cause cellular dysfunction, decreased muscle contraction ability, insufficient cellular energy supply, affecting muscle fiber function, and inactivation of some enzymes in the body, leading to a decline in body function and ultimately causing fatigue.
subjective feeling
Subjective feeling fatigue scale: Subjective feeling is closely related to factors such as exercise load, cardiopulmonary function, and accumulation of metabolic products, and is an important indicator for judging the degree of fatigue.
Power output test
Running and walking tests
V Jump Test
V-power bicycle
Muscle strength test
Biochemical indicators (invasion)
biochemical indicators |
Muscle fatigue evaluation based on biochemical indicators |
Blood urea (BUN) |
The greater the exercise load, the more significant the increase in blood urea. The next morning after training, blood urea increased by over 8.0mmol/L, indicating excessive exercise and fatigue accumulation. |
Serum testosterone to cortisol ratio (T/C) |
An indicator greater than 30% of the individual's normal value is considered overtraining. |
Blood lactate (BLA) |
The decrease in maximum lactate level and prolonged clearance time of blood lactate can indicate that the individual is in a state of fatigue during exercise. |
Urinary protein (P) |
The morning after exercise, if the exercise urinary protein content exceeds the normal value and increases day by day, it is considered excessive fatigue of the body. |
Creatine kinase (CK) |
CK activity increases after 5 hours of exercise, reaches its peak around 24 hours, and then falls back after 48 hours. If it does not decrease after a certain period of time, it is considered excessive exercise fatigue. |
Biochemical analysis of blood, urine, sweat, and saliva: The production of exercise-induced fatigue is closely related to the reduction of energy substances and oxygen supply, as well as the accumulation of metabolic products. Measuring this can to some extent evaluate an individual's level of fatigue.
physiological indicators
Surface electromyography (sEMG): The bioelectric signal formed by the superposition of the potential of skeletal muscle fiber motor units on the surface of the skin when the central nervous system controls muscle movement, known as surface electromyography signal. SEMG signals are sensitive to the physiological state of local muscles, and the acquisition process has advantages such as non-invasive, real-time, and multi-channel.
Muscle Movement Graph (MMG): MMG signal is a mechanical phenomenon that records the lateral vibration of muscles during active contraction. The change in internal pressure caused by muscle fiber contraction produces subtle vibrations on the surface of muscles, which can be amplified, observed, and quantitatively recorded by instruments. This signal is called MMG and is used as a unified term to describe the mechanical changes of muscles.
TMG (tension tomography): TMG monitors the state of muscles during intermittent electrical stimulation using high-precision digital displacement sensors. Due to the electrical stimulation, muscle fibers undergo lateral movement, and the magnitude of this lateral movement is proportional to the muscle strength and the type of muscle fibers.
Heart and lung related indicators
Heart related: Muscle fatigue depends on muscle blood flow and also on heart function. Therefore, monitoring and evaluating basic cardiac parameters can help assess muscle fatigue, with commonly used indicators including heart rate, post exercise heart rate recovery, and heart rate variability.
Pulmonary function related: The maximum oxygen uptake (VO2max) measured by a gas analyzer is a good parameter for evaluating muscle performance, which can reflect the body's ability to utilize oxygen per unit time. The maximum oxygen uptake decreases with muscle fatigue.
Nutritional/Supplementing Methods
Fatigue, Recovery, and Overrecovery
The theory of excessive recovery holds that under the stimulation of load, the functional levels of the body's energy reserves, material metabolism, and neural regulatory system decrease (fatigue). After load, these functional abilities can not only recover to the initial level before load, but also exceed the initial level in a short period of time, achieving the effect of "excessive recovery".
Autonomous and proactive recovery measures
Sports therapy mainly includes short-term jogging, fascial relaxation, vibration training, and passive stretching.
Sleep: Sleep is one of the best ways to eliminate exercise-induced fatigue. During high-intensity exercise and competitions, sleep time can be appropriately increased.
Psychological means: Psychological recovery methods can alleviate tension, relax muscles, and have good effects in eliminating fatigue. This method mainly includes relaxation training, psychological adjustment, self suggestion, etc.
Physical therapy, massage, acupuncture and moxibustion and other means
Physical therapy: methods such as cold therapy, heat therapy, and nerve electrical stimulation all belong to physical therapy, and many studies have confirmed that physical therapy has a restorative effect on exercise-induced delayed soreness.
Acupuncture and moxibustion and manual massage: acupuncture and moxibustion can eliminate exercise-induced fatigue by dredging channels and activating collaterals, relaxing tendons and activating blood circulation, and harmonizing the body; Manual massage has a good effect on relaxing muscles, eliminating muscle soreness, and restoring physical strength.
Other methods: traditional Chinese medicine, saline bath, hyperbaric oxygen chamber, negative oxygen ion therapy, etc.
Based on the above research, it can be concluded that there are still some application pain points in the field of muscle fatigue. For example, the key ways to improve athlete performance include regulating training load, assisting muscle recovery, monitoring peripheral fatigue, etc. The pain points are that the data accumulation, experimental plan formulation, and implementation of these improvement methods need to be scientific, precise, and normalized. Solving these pain points is the significance of our research.
In recent years, our company's quantitative research on muscle mechanics has been striving to address pain points in this field and is expected to become a standardized tool.
