The normal aging process and injury can result in a loss of strength and range of motion of the muscles. This is termed atrophy, and can be caused by both a reduction of the number of sarcomeres in a muscle as well as a shortening of the remaining sarcomeres. The number of nerve cells in the muscles also decreases, and the muscle fibers are replaced by fatty and fibrous tissues (known as “collagen”). Collagen does not stretch nearly as well as the sarcomeres. As we age, the collagen content in our muscles continues to increase, further weakening the muscle and reducing its range of motion. This effect can also be caused prematurely by immobility of the muscle, the classic – use it or lose it – syndrome. Yoga, obviously, counteracts this tendency, by using the muscles.

As muscles shorten due to age or immobility, they also become less flexible. The size change is due to fewer sarcomeres. The rigidity is caused by an increasing number of collagen molecules. This is the worst of all worlds we lose strength, size, and flexibility in muscles that grow older or are not used.

Yoga’s effect on muscles

Yoga can strengthen and lengthen the muscles: this is unique. Most forms of exercise that strengthen muscles also tend to shorten them. If a muscle is habitually held in a shortened position for long periods of time, due to strongly contracting the muscle, the body removes sarcomeres along the length of the fibers while adding them in parallel to the remaining sarcomeres.

As shown earlier, shorter muscles tend to become stiffer due to the increase in collagen. Yoga, however, lengthens the muscles, while they are being strengthened, stimulating sarcomeres to be added in both the horizontal and vertical directions. Yoga also prevents the increase of collagen.

Forward folds stretch the muscles along the back of the body
The myofibrils and their sarcomeres are not the only component of a muscle. What is not seen in the image shown earlier is the material that surrounds and supports the myofibrils. This is the fascia of the muscle, and it plays an important role in the strength and elasticity of the muscle. Our journey continues with a visit to our fascia.

(Next: Fascia )