Understanding Muscle Strength Principles and Scientific Training to Improve Fat Burning Efficiency

Strength is a fundamental component of physical fitness (speed, power, endurance, flexibility, agility, etc.), and the importance of developing strength in daily life skills is self-evident. A person's strength depends on the development of their muscles. In a sense, the basic methods used to train muscles and strength are the same.

I. Where Does Muscle Strength Come From?
Human strength is generated by muscle contraction. When we bend our elbow to move an object of considerable weight, the biceps brachii muscle in the front of the upper arm bulges high; this is the result of muscle contraction generating force.

It has been measured that a healthy person's muscles generate 8 kilograms of force per square centimeter. If all the muscles in the human body contract simultaneously in one direction, they can move a 25-ton weight, equivalent to the weight of six Liberation brand trucks.

In daily life, humans only need 70% of their physical strength to complete various activities. Moderate-intensity activities or physical labor require only 20% of their strength. During exercise, depending on the intensity, 70-90% of one's total strength is required (this is known as the second reserve capacity). The remaining 10% of strength is controlled by willpower and can only be utilized in sudden situations of tension. This is the principle behind "brute force in a crisis." Therefore, this 10% of the body's strength is called the third reserve capacity. This is because there is a gland at the upper end of each kidney called the adrenal gland. When a person is in an emergency, its secretion increases, leading to an increase in adrenaline in the blood, which accelerates blood flow, raises blood pressure, and promotes faster glycogen breakdown, releasing more energy and causing muscles to contract with greater force. Exercise physiology calls this extraordinary strength the "emergency response."

II. What Does Muscle Strength Depend On? All human activities are the result of the interaction between internal and external forces. Muscle work is accomplished by changes in its length and tension when excited. Muscle strength is expressed as the weight it can withstand at its maximum excitation. It mainly depends on five factors:

(I) The force generated by the contraction of a single muscle fiber. The maximum force a single muscle fiber can exert is 100-200 milligrams.

(II) Changes in muscle volume and mass. The number of muscle fibers in a person is determined 3-4 months after birth and does not increase or decrease throughout life. The more muscle fibers that make up a muscle, the greater the force it generates upon contraction.

(III) The initial length of the muscle before contraction and the speed of contraction. The shorter the initial length of the muscle before contraction and the faster the contraction speed, the greater the force generated; conversely, the longer the initial length and the faster the contraction speed, the smaller the force generated.

(IV) The state of the central nervous system. Muscle activity is controlled by the central nervous system. The more neurons controlling the muscle that are simultaneously excited, and the higher the frequency and intensity of nerve impulses transmitted from the central nervous system, the greater the force generated by muscle contraction; conversely, the fewer the neurons, the less the force generated. (V) The quality of the mechanical conditions exerted by muscles on the skeleton. If the muscle load is appropriate and the contraction rhythm is good, the mechanical effect on the skeleton will be good, and the force generated by contraction will be greater; conversely, it will be smaller. The appropriate load and contraction rhythm of muscles are not fixed. When the central nervous system is functioning well, the force generated by muscle contraction is greater; when the functional activity of the central nervous system and muscles improves, the appropriate load and contraction rhythm also increase accordingly.

Therefore, the magnitude of strength depends on the central nervous system's control over the muscles, the muscle's structure itself, and its cross-sectional area and volume. To "run fast, jump high, and throw far," consistent physical exercise, especially strengthening muscle strength training, to thicken muscle fibers, increase cross-sectional area and volume, and improve their quality, is the only way to develop muscles and increase strength; there is no other way.

III. The Relationship Between Strength and Age As mentioned earlier, the muscles of children and adolescents have different characteristics. It is precisely because of these characteristics that muscle strength has a direct relationship with age. According to measurements by A. Klobkov of the former Soviet Union, at ages 4-5, the strength of the wrist flexors and extensors was 5.22 kg and 4.61 kg respectively, while the strength of the trunk flexors and extensors was 8.17 kg and 4.65 kg respectively. From ages 11-14, the strength of the trunk extensors increased from 72 kg to 90.8 kg; from ages 14-17, it increased to 144 kg. Human strength begins to increase from ages 14-19, reaching its peak between ages 20-30. Domestic and international surveys show that diaphragmatic strength increases most rapidly between ages 10-13, and jumping height is about twice that of ages 8-9; this is more pronounced in girls than boys. The main reason is that children are active and like to run, jump, and play, which promotes the growth and development of lower limb skeletal muscles. As age increases, upper limb activity increases, and the strength of the arms and hands gradually increases. Grip strength increases most significantly between ages 14-16, more than doubling compared to ages 10-13. In my country, boys typically reach their peak height growth around 12-13 years old, and girls around 11 years old, marking their second growth spurt. During this age, muscles primarily grow longitudinally, resulting in lower muscle strength, poor coordination between muscle groups, weak joint stability, and high bone elasticity. Therefore, this period should focus on limb extension exercises and minimize or avoid medium to high-load strength training, especially static strength training. From 17-18 years old, height growth slows, and muscles begin to grow more horizontally, leading to increased strength. At this time, moderate to high-intensity exercises with moderate to heavy loads (compared to maximum strength) can be performed to increase muscle cross-section and volume, aiding in the development of strength. After age 20, all organs and tissues have matured, allowing for heavy-load, high-intensity, and even prolonged static and endurance strength training. This develops muscles, increases strength, and improves sustained endurance, benefiting both muscles and the cardiovascular system.

IV. Can Women Train for Strength? Traditional views discourage women from training for strength. They believe that: 1. Strength training increases muscle volume in women, and they will gain weight once they stop training; 2. It will significantly increase weight; 3. Muscles become stiff and lose elasticity; 4. Short bursts of intense exertion will lead to exhaustion. These "reasons" have no scientific basis.

Strength training will certainly increase muscle fiber thickness and muscle volume to varying degrees, for both men and women. However, compared to men, women have less muscle mass and lower strength, so their muscles will certainly not become masculine. Generally speaking, men are stronger than women. A normal adult woman's muscle mass accounts for about 35% of her body weight, while a man's is about 40%. Research by Marc Anderson in the United States has shown that women's muscle strength is only 60-70% of men's. There are indeed cases of women experiencing increased muscle volume in real life, but these are mostly due to anemia and the use of male hormones.

Muscle tissue is mainly composed of protein and water, while adipose tissue contains lipid compounds. Analysis of women undergoing strength training every two months has shown that body fat decreases and weight is reduced. This change in body composition makes women's figures more symmetrical, with a more harmonious ratio of muscle and fat attached to the skeleton. Moderate strength training not only avoids muscle stiffness and loss of elasticity, but also increases muscle length and elasticity, thereby increasing the range of motion of each active muscle group and further contributing to improved daily living skills.

Therefore, moderate muscle strength training for women not only develops strength and a healthy physique, but also enhances self-awareness and confidence, offering numerous benefits for learning, work, and life.

Section 3: How to Build Large Muscles The large muscle groups in the human body mainly refer to the trapezius, latissimus dorsi, deltoid, pectoralis major, rectus abdominis, biceps brachii, triceps brachii, gluteus maximus, quadriceps femoris, biceps femoris, triceps femoris, semitendinosus, semimembranosus, and soleus muscles—a total of 14 large muscles. In men, well-developed, angular muscles embody a combination of strength, power, and beauty; in women, these 14 muscles, when well-proportioned and not excessive, convey a sense of elegance and grace.

Height Increase: Over the past 20 years, the average height worldwide has increased by 1 centimeter every 10 years. Human stature shows a trend of each generation being taller than the last. Records show that in the United States, the national average height was 170 centimeters over 200 years ago, and has now reached 180 centimeters, an increase of 10 centimeters; in the past 30 years, the average height of 14-year-old boys in Japan has increased by 8.2 centimeters; in Sweden, from 1851 to 1931, the height of new recruits increased from 166.6 centimeters to 174.1 centimeters, an increase of 7.5 centimeters; and a study of the skeletons of 18th-century soldiers in the former Soviet Union found that the average height of soldiers had increased by 20 centimeters over the past 250 years. In the past 20 years, the average height of urban youth aged 18-25 in my country has increased by 2.3 cm for men and 2.15 cm for women.