2. Primary means of motion
Works in combination with the skeletal
system and the nervous system
Movement occurs when a nerve stimulates a
muscle to contract.
Muscle fibers shorten and pull on attached
bones to produce movement.
3. Skeletal muscles are made up of many muscle fibers held in place by
connective tissue (fascia).
Muscle fibers are made up of myofibrils (protein filaments) composed of a
series of repeating segments called sarcomeres.
Sarcomeres, made up of thick (myosin) and thin (actin) myofilaments, are the
functional contracting unit of skeletal muscle.
4. Sliding filament model
◦ If sufficient energy is
present, cross-
bridges are formed
and the myosin pulls
the actin toward the
center, thereby
shortening the
sarcomere and the
muscle fiber itself.
◦ See the video this
week on the Sliding
Filament Theory
5. Nerves are made up of neurons (nerve cells)
A motor unit is made up of one motor neuron
and all of the muscle cells it innervates.
The number of muscle cells a motor neuron
innervates depends on the precision and
accuracy required of that muscle.
6. Skeletal fibers can be divided into categories based on how
quickly they contract.
◦ Slow-twitch muscle fibers (also called slow oxidative or type I muscle
fibers)
As the name implies, slow-twitch fibers contract more slowly than fast-twitch
fibers. They have lower force outputs, but are more efficient and fatigue-resistant
than fast-twitch fibers.
◦ Fast-twitch muscle fibers (also called type II muscle fibers) are further
subdivided into fast-glycolytic (type IIx) and fast-oxidative glycolytic (type
IIa) fibers.
Type IIx have a limited capacity for aerobic metabolism, and fatigue more easily
than slow-twitch fibers. They have considerable anaerobic capacity, and are the
largest and fastest, and are capable of producing the most force, of all the skeletal
muscle fibers.
Type IIa muscle fibers possess speed, fatigue, and force-production capabilities
somewhere between type I and type IIx fibers. For this reason, type IIa fibers are
also called intermediate fibers.
7. Muscle Fiber Types
This chart is similar to Table 4.1 page 46
The following table compares the three types of muscle fiber using
the relative terms low, medium, and high.
Type I Type IIa Type IIx
Speed of Low Medium High
contraction
Force capacity Low Medium High
Fatigue resistance High Medium Low
Mitochondrial High Medium Low
content
Size Low Medium High
Efficiency High Medium Low
Aerobic capacity High Medium Low
Anaerobic Low Medium High
capacity
8. In a third-class lever, the motive force has a
short lever arm and the resistance has a long
lever arm.
Motive force muscles are at a mechanical
disadvantage.
◦ Muscles typically attach near the joint, creating a short
lever arm and, as a result, it requires relative high forces
to lift even small weights.
Application to training:
◦ Assuming a client is lifting the same amount of weight,
he or she can create more resistance by moving the
weight farther from the working joint, or less resistance
by moving it closer to the working joint.
9. Concentric contraction
◦ Muscle acts as the motive force and shortens as it
create tension.
◦ Motion is created by the muscle contraction.
Eccentric contraction
◦ Muscle acts as the resistive force and lengthens as
it creates tension.
◦ External force exceeds the contractive force
generated by the muscle.
◦ Motion is controlled (slowed) by the muscle
contraction.
10. Research suggests DOMS is caused by tissue injury
from excessive mechanical force, particularly
eccentric force, exerted on muscle and connective
tissue.
Generally appears 24–48 hours after strenuous
exercise
Attempt to reduce DOMS by starting at a low
intensity and progressing slowly through the first
few weeks while minimizing eccentric actions.
11. Strength
Power
Endurance
Reaction time, Quickness, Speed
Balance
Flexibility
Agility
12. Maximal force that can be exerted in a single
effort
Priority in sports that require a weighted
object to be lifted, carried or thrown.
Directly related to muscle cross-sectional
area.
Resistance training can increase the number
of fibers recruited for work.
13. Rate of doing work
Relationship of strength and velocity
Usually, the shorter the duration of the
activity, the greater the power needed
14. The ability to sustain submax contractions
Muscular power – Ability to repeatedly
perform a skill with adequate speed.
Table 4.2 (page 53)
◦ Strength-Endurance Continuum diagram
15. Reaction time
◦ Time elapsed from the stimulus until movement
starts
Quickness
◦ Reaction time plus the power of initial movement
Speed
◦ Final velocity attained
16. Dynamic
◦ Ability to maintain equilibrium during vigorous
movements.
Static
◦ Ability to maintain equilibrium in a stationary
position.
Task specific – need to practice specific
balance needed.
17. Range of motion through which joints are
able to move
Influenced by
◦ Joint design
◦ Tendons, muscles and ligaments
◦ Gender
◦ Habitual use
◦ Stretching
18. Sport Specific
Athletes should have slightly more range of
motion than their sport requires.
Flexibility can sacrifice joint stability
For most sports a moderate degree of
flexibility is adequate.
19. Ability to change speed and direction rapidly
with precision.
Practicing movements enhances agility
◦ Learning movements
◦ Reduced cognitive processing time
◦ Training specific muscle fibers
◦ Develops power specific to skill
