LIFETIME FITNESS
UNIT 4
UNDERSTANDING THE MUSCULAR SYSTEM
Muscular Strength is the amount of force that can be exerted by a single contraction of
the muscle.
Muscular Endurance is the ability of a muscle group to continue muscle movement over a
length of time.
Benefits of muscular strength and endurance
 Improved physical appearance
 Develop better posture
 Look firmer and trimmer
 Feel better
 Reduce risk of muscle injury
 Increase capacity to perform daily tasks and activities by reducing fatigue
 Reduce bone and muscle loss as you age
*Strength training improves weight control by building muscle which requires more calories
to supply energy than fat and increasing muscle mass which makes it easier to keep weight
off.
Muscle Basics
A muscle is a band of muscle fibers which contract (shorten) and enable the body to move.
These fibers extend the length of the muscle. Connective tissues attach bones and muscles
together.
3 types of connective tissue
 Ligament – connect bones together in a joint
 Tendon – attaches skeletal muscle to bones
 Cartilage – is found in a joint between bones and acts as a cushion at the end
of the bone
The human body has three types of muscles: cardiac, smooth and skeletal. Skeletal muscles
are located around joints and bones and enable us to move. Weight Training programs can
affect skeletal muscle.
There are three types of muscle fibers:
1. Slow-twitch muscle fibers which are slow to contract but have the ability to
continue working for long periods of time. They have rich blood supply and are
important for endurance-type activities such as long distance running and swimming.
2. Fast-twitch muscle fibers which are best suited for fast, short-term contractions.
These fibers are not well supplied by blood vessels and therefore have a reduced
capacity for using oxygen. They are used in fast, short burst activities required
speed and power such as sprinting and high jumping.
3. Intermediate fast-twitch muscle fibers which have characteristics common to the
other two fiber types. They have a better blood supply than fast-twitch. The
function of these fibers can be altered to meet demands of a specific exercise
program. They are used in activities of high intensity and moderate duration such as
middle distance running.
Hypertrophy is the enlargement of the diameter of a muscle fiber.
Atrophy is when the muscle fibers become smaller in diameter. This occurs when a muscle
is not used. *Muscles do not turn into fat if you stop training or stop using them. Muscle
cells have a different structure than fat cells.
Testosterone is necessary for the development of large muscles. Because men have thicker
muscle fibers and more muscle fibers than women and because women do not have the level
of testosterone that men have, women do not develop large muscles like men. Women’s
primary hormone is Estrogen. In addition, women have on average 8% more body fat than
men.
Types of Muscle Contractions
 Shortening or concentric contraction is a muscle contraction in which one end of the
muscle remains stationary while the other end pulls and turns the bone about the
joint. This type of contraction is used for pull-ups, curl-ups and lifting weights.
 Lengthening or eccentric contraction is a muscle contraction which involves a
gradual release of the contraction; often called lengthening contraction. When you
lower the weight or your body in a chin-up, you are using an eccentric contraction.
 Static contraction is when the muscle remains in partial or complete contraction
without changing its length. An example is pushing a wall or one hand against
another for 10 seconds.
As you exercise a muscle, several changes take place. Effects of exercise on the muscular
system include:
o Size of the muscle temporarily increases as the blood flow increases
o Body temperature rises due to the increased activity in the muscle tissue
o Increased temperature causes the muscles to become more flexible, able to
contract and relax more easily, and contract at a faster rate
o Number of red blood cells increases
o Additional capillaries develop
ACHIEVING MUSCULAR FITNESS
*Weight training can increase muscle mass, bone mass and connective tissue thickness, as
well as improve speed, power and endurance.
Repetition is the number of repeated lifts or movements performed
Set is a group of successive repetitions without rest
Muscular Strength Max is the total amount of weight you can properly lift through the full
range of motion
Muscular Endurance Max is the total number of times you can perform an exercise through
the full range of motion
Applying the Principles of Training to Muscular Fitness
In order for a muscle to grow and become stronger, it must be challenged
Principle of Overload
Frequency – a minimum of 48 hours of rest is necessary between workouts to allow the
muscle group recovery time. If you want to work out every day, do upper body one day
and lower body the next day.
Intensity
 MS – 60 to 80% of maximum lift
 ME – 30 to 50% of maximum lift
*It is important to increase intensity gradual so that you do not injure
muscles.
Time
 MS – 8 to 12 repetitions
 ME – 12 to 20 repetitions
*Lift the weight on the count of two (concentric contraction), pause,
lower the weight on the count of four (eccentric contraction). The
greatest strength gain is made when the weight is lowered.
Principle of Progression
MS – begin with 8 reps and gradually increase to 10 then 12. Increase the % of max
and drop back on reps. Then build back up to 10-12 reps
ME – increase repetitions
Principle of Specificity
Work exact muscle group you wish to develop. For Example, arms – pushups, tricep
extension, bicep curls and for legs – leg curls, wall sits, leg extensions
Safety Precautions
 Warm up properly
 Secure barbell plates to prevent slipping
 Breath rhythmically as you exercise
 ALWAYS USE A SPOTTER (someone who assists the weight lifter) WHEN
WEIGHT LIFTING
Types of exercises to increase Muscular Strength and Muscular Endurance
1. Isometric Exercise is strength building exercises in which you contract, or tighten
muscles without changing their length (static contraction).
2. Isotonic Exercise is one where training involves lifting a resistance through a range
of motion (eccentric and concentric contraction). The muscle will not be exercised
to the same extent as it goes through the range of motion. The weakest joint
position will determine how much weight you can lift. Lifting weights using barbells,
dumbbell bars and weight machines are examples of isotonic exercises.
3. Isokinetic Exercises is one in which muscle tension is kept at a max through the full
range of muscle movement. Requires special machines.