Muscle Mass and Aging

March 31, 2014

   Your skeletal muscles, also known as lean muscle, are the muscles that attach to your bones and are under voluntary control. As you age your skeletal muscle mass starts to deteriorate. I'm writing this post with the thought that I can give you a realistic sense of what happens to your muscles as you age, and then I'll conclude with the good news about weight bearing and aerobic exercise.

   Starting at age 40, muscle mass begins to decline. It accelerates by 50. Bone mass or density loss in women after menopause is common and our bones begin to lose calcium and other minerals. The rate of muscle loss is faster than the muscle we gain. Our bodies don't work as efficiently as they used to, which leads to a slower metabolism and fat accumulation. Muscle weakening or atrophy sets in. The reasons for atrophy are many. I will share four of them with you: age, sedentary lifestyle, medications and disease.

Age Related Changes in Muscle

   Muscles lose their size and strength as we get older, which contributes to fatigue, weakness and less tolerance to exercise. This is due in part because the number of muscle fibers start to reduce in size and numbers. Muscle tissue is also replaced more slowly. As the nervous system changes, muscles become less toned and the ability to contract them gets more difficult. Bone structure changes result in a loss of bone tissue, calcium and other minerals making this another contributing factor. Joints lose their lubrication (synovial fluid) becoming stiffer and less flexible.

Sedentary Lifestyle 

   You've heard the saying, "use it or lose it". Inactivity causes our joint cartilage to shrink and stiffen, reducing joint mobility. A sedentary lifestyle causes muscles to lose their mitochondria. The main function of the mitochondria is to produce energy for various parts of the body. It burns fat or sugar for energy. If the body does not need energy, fat gets stored. This fat increases the number of fat cells in the body making it harder to lose weight. Being sedentary increases the body's capacity for fat storage, which results in a greater chance for developing high levels of LDL or bad cholesterol. A common thought is that this inactivity causes transdifferentiation (a conversion of one differentiated cell type into another) resulting in the muscle cells changing to fat cells. The body gets signals that it no longer needs those muscle cells.


   There are a few medications prescribed for specific conditions that cause muscle weakness. One of those medications is systemic corticosteroids, often prescribed for people with asthma or inflammatory conditions such as rheumatoid arthritis or lupus. Statins are used for preventing and treating atherosclerosis that causes chest pain, heart attacks, strokes, cholesterol and diabetes - muscle pain is one of the side effects.


   Many chronic diseases commonly cause muscle weakness. In some conditions this is due to reduced blood and nutrient supply to the muscles. Chronic kidney disease, anemia, lung disease, heart disease, diabetes, depression, peripheral vascular disease, chronic pain are some of these diseases. Osteoporosis is a disease directly related to the gradual loss of bone proteins and minerals resulting in fragile bones making an individual more at risk for fracture.

Exercise and Strength Training

   The good news is that strength training can address just about all of the above issues. And, you can start - with a doctor's approval - at any age.

  The beneficial effects of strength training include replacing muscle, reducing fat, increasing metabolic rate, relieving or decreasing low back and arthritic pain, lowering blood pressure, minimizing osteoporosis, enhancing glucose utilization, mitigating depression and improving blood lipid levels.

   The amount of exercise on regular basis should be reasonable and represent a doable commitment of time. Lets face it, if it becomes another chore we will discontinue it like all the rest of those disliked chores. Aerobic activity should be 5 days a week of moderate intensity for a total of at least 150 minutes according to ACSM guidelines.

   Muscles are the engine of the body. Strength training enables these muscles to get stronger, helping us to use them more effectively and with less effort. For musculoskeletal fitness the recommendations is 8 to 10 resistant exercises performed 10 to 15 times each as a set 2 to 3 days a week, according to ACSM guidelines.

   I strongly feel that exercise and strength training are essential to living a healthy and productive long life.