Muscles Carry Out the Physical Chores of the Body


Trillions of myocytes, or muscle cells, make up muscle tissue. Each can contract by sliding proteins, known as actin and myosin, past one another. Their ability to change shape allows them to generate the collective tensile force that carries out the body’s physical work:

  • Movement
  • Maintaining posture
  • Breathing
  • Temperature regulation
  • Communication
  • Blood circulation
  • Blood vessels and organ constriction

Muscles conduct the work that keeps every other tissue and organ in our bodies healthy. That explains why athletes, who focus on developing and training muscles, have such excellent health. Muscles also store and regulate materials, like amino acids and glucose, making them critical to the health of every cell in the human body.

A Decline in Muscle Mass Affects Health Throughout the Body

Because muscles support all tissues, diseases associated with muscle health can lead to the onset of ailments in other organs. For example, age related muscle loss not only causes decreased strength but also impacts metabolism and oxygen consumption. It affects every cell in the human body and can lead to the total debilitation that prevents many mature adults from leading independent, satisfying lives.

A healthy diet balanced with exercise and rest can provide the nutrients and stimuli to keep muscles strong and functional. Because muscle health benefits every cell in the body, it reduces disease risk and helps maintain vitality.

Muscle loss occurs when the body breaks down protein faster than it can synthesize it. After age 40, the average person loses 1-1.5% of their muscle mass every year. This rate increases over time until by age 80, the average person will have lost 30–40% of their total muscle mass and 20-40% of their strength. While this is a natural part of aging, other factors can accelerate the process. Illness, injury, inactivity and inadequate nutrition are key culprits that can increase the rate of muscle loss and damper the body’s ability to rebuild lost muscle.

Even a person who experiences minimal muscle loss can still feel the effects. They may not be able to exercise as long or train as intensely. They may not be able to carry a bag of groceries up a flight of stairs without feeling fatigued. They’re often more likely to suffer an injury. Over time, if muscle loss continues, it can impact overall quality of life.

What causes muscle loss?

  • Illness or injury
  • Excessive physical stress or overtraining
  • Dieting and calorie restriction
  • Inadequate nutrition
  • Reduced activity

Poor muscle health negatively affects:

  • Weight and body composition
  • Athletic performance
  • Ability to carry on a healthy lifestyle
  • Joint health and mobility
  • Overall quality of life
  • Metabolic health

Muscle is essential to metabolic function, strength, endurance and overall health and well-being.

In addition to its primary tasks of maintaining and supporting locomotion, breathing, and posture, muscle is critical for maintaining balance in whole-body protein metabolism. In the absence of nutrient intake, muscle acts as an amino acid store, allowing your body to maintain protein synthesis within vital tissues and organs. In other words, during nutrient deprivation, your body relies on muscle to maintain normal bodily function.

Other benefits of healthy muscle include:

  • Reduced risk of injury. Strong muscles can improve balance and reduce the risk of falling.
  • Being able to stay active and exercise or work more helps maintain bone strength.
  • Increased metabolic rate. Your metabolic rate is the rate at which the body burns calories. Muscle burns significantly more calories than fat—one pound of muscle burns 7–10 calories per day, compared to one pound of fat, which only burns 2–3 calories per day.

Pt. 1 – Understanding Protein

After water, proteins are one of the largest components in the body and are also sometimes called “the building blocks of life”. Proteins are made up of many smaller units called amino acids. Some amino acids are called “Essential” amino acids because they cannot be produced by the human body. Instead, they must be acquired through diet. Our bodies can’t store individual amino acids, thus necessitating a daily consumption of amino acids via proteins.

Pt. 2 – Protein & Muscle Health

To improve physical muscle function and strength, adequate protein intake is needed. The proteins supply the amino acids which not only stimulate the synthesis of myofibrillar proteins (the basic unit of muscle cells) but also mitochondrial proteins necessary for producing energy, thus it is likely that increasing amino acids through protein intake improves overall metabolic function of muscle.

To maintain healthy bodily function, we constantly metabolize proteins to replace what’s been damaged through normal function or by external stressors such as training, activity, illness or injury. Ideally, protein synthesis (making new proteins) and protein breakdown (releasing amino acids from protein) are in balance. When protein breaks down faster than it is synthesized, we generally lose muscle mass. A common misconception is that increased protein consumption alone can remedy the problem.


Increased Protein Intake Cannot Always Solve the Muscle Loss Problem

While consuming protein will offer some support, consuming enough protein to effectively counteract the effects of muscle loss may not be realistic, and other underlying factors such as age may reduce the response of muscle to increased protein consumption. Consuming a high quality protein such as those found in animal products, or a mix of plant proteins is one way to make sure we do get adequate protein intake. In general it is accepted that 30 grams of high quality protein consumed three times per day (morning, noon, and evening) supplies adequate amino acids for most adults.

Increasing protein intakes much above this generally do not provide any additional benefit and may in fact supply unwanted calories.

Betts, J.G., P. Desaix, E. Johnson, J. E. Johnson, O. Korkol, D. Kruse, B. Poe, J.A. Wise, and K.A. Young. 1999-2018. Chapter 10: Muscle Tissue, in Anatomy and Physiology, Open Stax
Reviewed 16 May 2018.
Dideriksen, K., S. Reitelseder, and L. Holm. 2013. Influence of Amino Acids, Dietary Protein, and Physical Activity on Muscle Mass Development in Humans. Nutrients. 2013 Mar; 5(3): 852–876, on the US National Library of Medicine, National Institutes of Health website
Reviewed 17 May 2018.