Muscle

Muscle Anatomy

Muscles will attach to bones by means of a tendon.  Muscles consist of fascicles which are groups of muscle fibers called myofibrils.

A myofibril is a basic rod like unit that contains longer chains of sarcomeres.

Sarcomeres are the place where muscle contraction takes place.  In a sarcomere there are two main protein filaments.  Actin is the thin filament and myosin is the thick filament.  When muscle contraction takes place actin and myosin overlap, yet maintain their length.  Concentric contraction is the term used when muscles shorten and eccentric contraction is when muscles lengthen.  When they stay the same length, it is called isometric contraction.


 https://andreacollo.wordpress.com/2013/11/06/muscle-contraction-and-emg-analysis/

Hypertrophy is an increase in the size of muscles.

Hyperplasia is an increase in muscle fibers.

How muscles grow

Skeletal muscles are the most adaptable type of muscles, they are made to lengthen and strengthen according to the body’s needs.  As bones grow or exercise occurs, sarcomeres increase in length and thickness.  As myofibrils thicken, they split at both sides of the muscle and become new sarcomeres.

What causes/influences muscles to grow?

Hormones are critical for sarcomere development; these include growth hormone, IGF-1, testosterone, insulin and thyroid hormone.  Testosterone stimulates the number of myofibrils to increase and also helps release growth hormone.  Growth hormone and IGF-1 work together to increase protein synthesis, causing both bones and muscles to develop.   Insulin and thyroid hormone help muscles mature.

Another factor that causes muscles to grow is bone growth.  As bones lengthen the muscles must lengthen as well.  The muscles begin to stretch to keep in alignment with the bone; this sustained stretch leads to an increase in the number of sarcomeres.


Lifestyle Changes in Muscle

Muscles allow a person to move, and the development and decline are important to understand so that we can fully enjoy and live life.  In early development, it is important for parents to make sure their children are receiving proper nutrients and exercising in healthy, beneficial ways.  By the time we age it may be too late to fully repair damage to muscles, so here is some information to help build and maintain healthy muscles.

Childhood-Adolescence Muscle Development

 Young children are developing and are generally very active so while weightlifting helps with postural control as well as improve strength it is not recommended and can be harmful for young children.

 After the age of 7, children have postural and muscle control so controlled and regulated exercise can become beneficial.

In middle childhood to preadolescence strength training can become beneficial as long as it is properly regulated.  At this point in development there is not really a significant gain in muscle size but there is a gain in neural development.  Strength training can help a child develop sports skills and can create better postural control. 

Post pubertal adolescents benefit from strength training as their muscles being to increase in size (hypertrophy).  Resistance training can also help prevent injuries for people in this age group.

Muscle Decline

In a person’s mid-20s to early 30s muscles begin to age.  The specific changes that occur at this time are changes in muscle strength, structure, size, fiber type (type II) and contractile characteristics.  These changes become visible in athletes, as muscle mass decreases, we see a decrease in speed or athletic ability.

Sarcopenia

Age related muscle loss is known as sarcopenia.  With sarcopenia comes a loss of muscle mass, loss of muscle function, a decrease in quality and a decrease in size of muscles.  Exercise conditions muscle so if a person remains physically active and exercises it will prevent cellular damage, and help keep a person from losing muscle structure and function.

People with sarcopenia are encouraged to participate in resistance training as it increases muscle gain (increase in muscle fibers).  Resistance training should occur 2-3 times a week and a person should do 6-8 reps with 1-2 reps of higher intensity sets.