S. Norman

 Skeletal Muscle—attached to the bones of the skeletal system ◦ Voluntary muscle—contraction of skeletal muscle is a result of conscious voluntary control  Smooth Muscle—primarily lines hollow internal structures (blood vessels and digestive tract) ◦ Involuntary muscle—contraction and relaxation phases are automatic  Cardiac Muscle—found only in the heart ◦ Involuntary

 A motor nerve coming from the brain or spinal cord causes a muscle to contract or a gland to secrete  A motor unit consists of a single motor nerve and all the muscle fibers to which it sends impulses  A motor nerve is connected to many muscle fibers, but each muscle fiber is controlled by only one motor nerve  Very fine movement, very few muscle fibers  Large or heavy movement, many muscle fibers

 A muscle fiber contracts completely or not at all.  If a stimulus for contraction is below the threshold value, the muscle does not contract  If the stimulus is above the threshold value, the muscle contracts completely  All of the muscle fibers in a motor unit contract completely or not at all.

 Muscle tissue can contract or relax—muscle can pull on bones or stop pulling on bones  Muscle tissue can only pull—it cannot push  All exercises involve muscles pulling on bones across a joint. The movement that takes place depends upon the structure of the joint and position of the muscle attachments involved.  Types of contraction are: isometric, isotonic, concentric, eccentric, and isokinetic

 Iso means equal, metric refers to length or measure  Muscle maintains an equal length  Contracting a muscle and creating a force against an immovable object  Muscle contracts and tries to shorten but cannot overcome the resistance  Example: Pushing against a wall or trying to lift a truck

 Tonic means tone or tension.  Movement occurs but muscle tension remains about the same.  Example: a complete barbell curl  External resistance remains constant, however, the muscle does not maintain constant tone throughout the exercise movement because of the continuous change in its angle of pull on the bone.

 Result in the muscle fibers shortening as tension develops, causing motion in a joint  Muscle becomes shorter and overcomes resistance  Example: lifting the weight upward during the biceps curl, pushing outward on the leg press

 Lengthening contraction  Muscle contracts and tries to shorten but is overcome by the resistance  Allow you to lower things smoothly and slowly  Example: lowering weight in a smooth, controlled manner during the biceps curl

 iso = same, kinetic = motion  Constant-speed contraction  Muscle can contract at 100% throughout the full range of motion at a constant speed  Example: injury evaluation/rehabilitation

 Muscles that are not used will shrink to a size that is adequate for the demands placed upon them  Example: broken leg or arm put in a cast, when the cast is removed the arm or leg will be much smaller than the active arm or leg  Both limbs will be reduced in size gradually (often unnoticed) when one does not train the muscular system

 Muscles that are forced to work harder than normal generally increase in size  Women < Men  Men have more testosterone and a larger number of muscle fibers in a muscle

 Specificity—You must exercise the specific muscles you want to develop, and follow specific exercise guidelines to produce the specific type of change you desire (strength, size, endurance)  Overload—The muscle to be developed must be overloaded or forced to work harder than normal  Progression—The workload must be increased progressively as the muscle adapts to each new demand (written record)