Download #7 - MUSCULAR SYSTEM There are 3 types of muscles within the

#7 - MUSCULAR SYSTEM
There are 3 types of muscles within the body:
1) SKELETAL MUSCLE – attaches to bones and makes movement possible.
2) SMOOTH MUSCLE – makes up walls of hollow internal organs such as the
stomach or blood vessels.
3) CARDIAC MUSCLE – found only in the heart.
Smooth muscle and cardiac muscle is called involuntary because you do not consciously control their
movement. Skeletal muscle is called voluntary because you can control movement.
STRENGTH is the amount of force a muscle can exert. All of us need strength to perform our daily activities.
If you use muscles regularly they will stay strong. If not, they will weaken. Strength in muscle relates to good
health by helping you: 1)maintain good posture, 2)reduce fatigue, 3)prevent muscle injuries and soreness,
4)prevent backache.
FUNCTIONS OF MUSCLES: 1) MOVEMENT – when muscle fibers contract, they pull on the parts to
which they are attached-usually creating movement. 2) RESIST MOVEMENT – at times, muscle contraction
resists motion. 3) MOVEMENT OF BODY FLUIDS – such as blood and urine. 4) HEAT PRODUCTION
– which aids in maintaining body temperature.
SKELETAL MUSCLE
Skeletal muscle usually attaches to bones, is voluntary and is used to create movement. Skeletal muscles are
made up of bundles of muscle fibers. These fibers control movement by contracting and relaxing. Connective
tissue surrounds each muscle and attaches to bone with a cordlike tendon. Although muscle fibers and the
connective tissue associated with them are flexible, they can be more fibers injured, the more severe the injury.
Muscles use oxygen when contracting. The oxygen needed is carried from the lungs to the muscles by blood
(red blood cells). The more a muscle works (contracts), the more oxygen is needed. Although muscles can
store some oxygen temporarily, eventually muscle cannot get enough oxygen. The process of using stored
oxygen in a muscle creates a substance called lactic acid. An accumulation of lactic acid causes a muscle to
lose its’ ability to contract and sometimes causes cramping.
Principles of Strength Exercising
Overload – a muscle must contract harder than normal if it is to become stronger; a muscle must work more
than normal.
Progression – overload gradually, increase the load over a period of time to get the best muscle strength.
Specificity – exercise the specific muscles you want to develop. Leg exercises develop the legs, arm exorcises
develop the arm, etc.
The F. I. T. FORMULA
FREQUENCY – refers to how often you exercise. For exercise to be of a benefit, you need to exercise at least
three times a week.
INTENSITY – refers to how hard you exercise. Exercising too easily will not improve your fitness and
exercising too hard can make you sore and increase the risk of injury.
TIME – refers to how long you exercise. You need to exercise 20 to 30 minutes at one time to improve your
fitness.
IMPROVING MUSCLE STRENGTH
You must exert muscular force against a resistance to improve muscle strength.
ISOTONIC EXERCISES are those in which muscles contract and body parts move – such as lifting weights
or doing calisthenics.
ISOMETRIC EXERCISES are those in which the muscle contracts when working against stationary object.
The muscles work, but the body parts do not move. Isometric muscles are often recommended after an
extended period of inactivity, such as a broken limb.
MUSULAR ENDURANCE – is the ability of a muscle to work for long periods of time without getting tired.
Muscular endurance depends on the kind of muscle fibers that make up the muscles. There are 2 kinds of
muscle fibers: The first are SLOW-TWITCH FIBERS. These contract at a slow rate. Slow-twitch fibers 1)
use oxygen from the blood to release energy 2) do not tire easily 3) have the most endurance of all muscles.
FAST-TWITCH FIBERS contract at a fast rate. Fast-twitch fibers 1) do not use oxygen from the blood to
release energy 2) have greater strength and 3) have less endurance. The relative number of the kind of fibers
in a given muscle does not change, but the kind of exercise you do influences the size of the fibers and their
ability to use oxygen.
LOW INTENSITY EXERCISES - build the muscular endurance needed for daily activities – use only the
body parts you use daily (in other words, do nothing).
MEDIUM INTENSITY EXERCISES - build the muscular endurance needed for good fitness. Do exercises
and body weight calisthenics (pull-ups, push-ups, etc.).
HIGH INTENSITY EXERCISES - build muscular endurance for high-level performance. Combine strength
training with increased repetitions for endurance.
Critical Thinking Questions
Please be thorough and use the information presented in the hand-out
1.
2.
3.
4.
How do you improve your fitness?
How does the F.I.T. formula apply to all exercise programs?
Why might exercise be more difficult at higher elevation?
Compare and contrast Isotonic and Isometric exercises. Explain the advantages and disadvantages of
each.
5. Explain the difference between involuntary and voluntary muscles. Why is it important that they
function the way they do?