Differences in muscle mass and functions between the genders are frequently in the news. Basic body composition differs significantly between women and men, with females having a higher percentage of body fat and males having more lean muscle mass.
Skeletal muscles are the body’s most abundant tissue. Their different fibers contain over 3,000 variously expressed genes that affect composition and contractility, along with variances in hormone regulations.
How Do Muscles Work?
Over 600 bodily muscles perform varied functions, including walking, breathing, running, speaking, digestion, and circulation. Skeletal muscles often receive the most focus as they are the most abundant in the body. These muscles connect ligaments, tendons, and bones to support the body’s actions.
Skeletal muscles contain horizontally striped (striated) fibers that contract to power movements. Signals from the brain tell skeletal muscles to move via electrical signals that flow through the spinal cord, sending messages through peripheral nerves to the muscles. Through contracting and relaxing, muscles move the various parts of the body, with the motor cortex on the left side of the brain stimulating movements on the right side of the body and vice versa.
Muscles pull on the tendons to activate the movement of the skeletal bones. When the movement is complete, the nervous system sends messages that relax the muscles to return the bone to its resting position.
Sarcomeres are the muscle fiber’s contractile units composed of actin and myosin, two protein filaments responsible for contractions.
How Do Hormones Affect Muscle Growth?
Hormones regulate nearly every function of the body, and when their levels are out of balance, the body can experience breakdown. Such is the case with hormones and muscle growth.
Balanced hormone levels keep our bodies in shape and functioning correctly. Some hormones play a significant role in muscle growth, with human growth hormone (HGH) and testosterone leading the way. People often ask about comparing HGH vs. testosterone and which is more beneficial for muscle growth.
Anabolic hormones are what your body requires to increase muscle mass through anabolism, a process where energy usage constructs molecules from smaller units. Both testosterone and growth hormone are crucial for maintaining and protecting muscle mass.
An easy way to know the answer is to look at the following anabolic hormones to understand their impact on muscle mass:
- Testosterone
Although often viewed as the leading male sex hormone, testosterone is equally vital for women as it helps regulate muscle and bone mass, fat distribution, strength, and libido. People with lower testosterone levels often have more body fat and less muscle mass.
Testosterone increases satellite cell numbers, affecting hypertrophy (muscle cell growth). Androgen receptors expressed in muscle cells and fibers respond to testosterone stimulation.
- Growth hormone
The most influential hormone in muscle growth might be HGH, which stimulates cell regeneration. One of the ways it helps promote lean muscle is through the support of insulin growth factor 1 (IGF-1), a hormone produced by the liver via HGH stimulation. IGF-1 is the leading mediator of growth hormones’ cell-regenerating effects.
The body uses HGH during sleep to support tissue repair. If HGH levels are low and not enough growth hormone enters the bloodstream during sleep, the tissues cannot adequately heal from any overexertion, such as weightlifting, during the day.
- Insulin
Another anabolic hormone, insulin, transports amino acids from the breakdown of food into the muscles for tissue repair. Insulin sensitivity can change due to diet, body fat, exercise, and other factors, which can alter muscle growth.
- Insulin-like growth factors
IGF-1 is the leading mediator of HGH effects on cell regeneration, muscle repair, and growth. Low HGH levels can lead to declining IGF-1 production, decreasing lean muscle, and increased fat mass.
How Does Cortisol Affect Muscle Growth?
Unlike anabolic hormones that help build and support muscles, catabolic hormones like cortisol inhibit muscle growth by releasing energy. Cortisol is the body’s leading stress hormone that protects during emotional or physical stress. It opposes growth hormone and testosterone, so when cortisol levels are high, GH and testosterone are low.
Cortisol levels can increase during times of lengthy cardio workouts, as well as during anaerobic or strength-training exercises. Combining weight training and aerobic exercise increases cortisol levels, which could speed muscle breakdown. Increased catabolic and decreased anabolic hormones cause the body to lose muscle mass.
Physical Differences Among Genders
The most understood difference between men and women is that males naturally have higher muscle mass per weight than females. Genetics and fitness levels can alter that, as women who engage in weight training have more muscle mass than body fat compared to those who do not exercise regularly.
Although women have a higher body fat percentage than men, the way they store fat in their hips and thighs, compared to male fat storage in the abdomen, is associated with a lower incidence of obesity-related diseases, such as type 2 diabetes. The role of genes and hormones is evident, as higher estrogen than testosterone levels in women influence the difference.
Male fatty tissue contains fewer mitochondria (cellular energy producers) than female fatty tissue. However, hormonal changes during menopause reduce the protective effect of estrogen.
Because women use fat for energy during exercise, low-to-moderate intensity workouts of longer duration are often beneficial. Men often do better with high-intensity bursts, as their edge in explosive strength burns more glucose. However, longer recovery times are often necessary.
Differences in Muscle Composition
The most significant differences in muscle mass are associated with type I muscle fibers, with women having significantly more of these slow-twitch muscle fibers than men. However, males have a higher type I muscle fiber area. Because type 1 fibers have greater capillary density and blood-carrying myoglobin, they increase fatty acid oxidation and deliver increased blood to the muscles. As a result, female muscles are more efficient at processing glucose.
While female muscles are more resistant to fatigue and recover quicker, male muscles have higher maximum power output, capacity for anaerobic metabolism, and speed. Males have a higher proportion of type II (fast-twitch) muscle fibers than women. One factor is that men use protein and carbohydrates more than women, who rely on fats as their leading fuel source.
Conclusion
Numerous factors, including genetics, gender, hormones, nutrition, and lifestyle, influence muscle function and growth. Maintaining hormonal balance is crucial to ensuring a healthy body.
Understanding the differences between male and female muscle mass, growth, and function can help you determine the appropriate lifestyle changes, including nutrition and exercise. Checking your hormone levels can help protect the body’s structural integrity, as proper muscle mass protects the bones against fractures.
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