Muscles

Function of Muscle 1.Muscle tissue is responsible for all body movements. This includes body motion as in walking but also organ movement such as dilation of blood vessels or heart contraction. 2.Muscles support the functions of most our systems that keep us alive: ie – respiration, digestion, blood circulation … 3.Heating of body, muscle contractions give off heat and help maintain body temperature. Shivering warms the body when muscles in the skin contract reflexively due to cold.

How Many?? There are over 600 different muscles in our body. Some are very large for gross motor movement (kicking a ball) and some very tiny fine motor control (blinking).

Muscle Tissue Skeletal, Cardiac and Smooth

Cardiac Muscle Found only in the heart. Able to contract independently of the brain but requires signals from the brain to beat in correct sinus rhythm.

Smooth Muscle tissue is found in the organs and vessels of the body. Smooth muscle tissue is called Involuntary muscle as it does not require conscious commands from the brain in order to operate

Anatomy of a Skeletal Muscle Skeletal muscle attaches to bone and moves our skeleton Skeletal Muscle is called Voluntary Muscle as it requires conscious commands from the brain in order to move and operate Muscle fibres are wrapped together by a sheath (perimysium) to create a muscle Bundle. Muscle Bundles are grouped together and wrapped in a sheath (epimysium) to create a muscle body like a Bicep.

Muscle Fibers Muscle Fibers are about the diameter of a human hair, they can contract about ½ their length and can lift about 1000 times their weight. Muscle Fibers are malleable meaning they can stretch When stimulated by an electric impulse they can contract to their full potential (about ½ their length). Once contracted they need to be pulled back by another force to return to their original length.

Motor Unit A motor unit consists of the nerve (neuron) and all the fibers connected to it. When a neuron is stimulated all of its fibers will contract completely. This called the All or None Principal. The number of motor units stimulated the stronger the muscle contraction and vice versa.

Gross Motor Movements Big muscles with small # of motor units but each motor unit controls large numbers of muscle fibers

Fine Motor Small muscles with lots of motor units to control them but each motor unit controls small numbers of muscle fibers.

Muscle Pairs Agonist and Antagonist Example – Muscles work in pairs to counteract each other’s movement. Example: the bicep is called the agonist (primary mover) and the tricep is the antagonist (returns the arm to its original position).

Eccentric, Concentric and Isometric Contractions

Tendons, Origin and Insertion Tendons connect the muscle to bone. Origin is the connection we call an anchor, it does not move during the contraction Insertion is the connection that moves a bone during the contraction.

Muscle Strength Muscles can adapt to use. Muscle fibres get thicker and stronger if they are exercised regularly over time.

Micro Tears, Overload, Rest and Recovery Strength Training During weight resistance training we try to overload a muscle. This means work it beyond its normal strength This results in micro tears in the muscle fibers During rest and recovery over the next 24 hours the tears heal and make the fiber a bit larger in diameter and as a result stronger Over time repeated training will result in larger stronger muscles.

Flexibility – muscles will lengthen if stretched regularly over time. Better flexibility reduces risk of muscle injuries

Muscle Concepts Transient Hypertrophy – Muscle temporarily get larger during exercise due to increased blood flow. This lasts only for 30 minutes or so after exercise. Does not increase strength. Chronic Hypertrophy – Muscle fibers diameters get bigger as they adapt to repeated exercise training. As fibers get larger the muscle gets bigger and stronger over time. Muscle Atrophy - Muscle fiber diameters get smaller over time as a result of lack of use or training. Results in loss of strength. Hyperplasia – An unproven theory that increases in strength due to exercise actually result in muscle fibers splitting and increasing in number to account for increased strength. Voluntary Muscle – muscles that we consciously control like leg muscles for walking Involuntary Muscle – muscles that function without conscious control like our organs – blood vessels, stomach, heart…

Transient Hypertrophy the muscle increases size from increased blood flow, temporary (30 min) and no strength gain

Chronic Hypertrophy – muscle gets larger and stronger from training

Muscle Atrophy – muscle fibers shrink from disuse The person above had their leg in a cast for some time and the leg atrophied from lack of use. It can regain its former strength and size with time and exercise.

Muscle Injuries Ouch!

Muscle Strain and Tears Symptoms: Pain, Weakness & Function

Muscle Strains/Tears

Treatment of muscle injury Rest – it takes time for the muscle to repair Ice – helps reduce the swelling and pain Compression – helps hold muscle in line and reduce the pain and swelling Return to action when function is no longer impaired. Returning too soon may result in re injury