Pages 59-60: Questions # 4 to 15 inclusive [answers are in bold print]
4. Differentiate between active and passive insufficiency in two-joint muscles.
Active insufficiency occurs ina two-joint muscle when it cannot
shorten enough to cause full range of motion of both of the joints it croses
at the same time. Examples:
- triceps brachii during shoulder extension and elbow extension
- gastrocnemius during ankle extension and knee flexion
Passive insufficiency occurs when the muscle cannot be stretched
enough to permit full range of motion at both joints at the same time.
Examples:
- biceps femoris during knee extension and hip flexion
- quadriceps femoris during knee flexion and hip extension
5. With the elbow flexed 90 degrees and the wrist in anatomical position, flex the fingers. With the elbow in the same position but with the wrist flexed 90 degrees, repeat the finger flexion. What is the difference in the ROM that the fingers display in the two situations? What is the name of this phenomenon and the reason for its occurrence?
Passive insufficiency of the multijoint muscles of the extensors of the wrist and fingers should limit finger and wrist flexion when they are performed together. Greater range of motion of wrist flexion should be possible with the fingers extended.
6. Flex the shoulder joint 90 degrees, and then flex the elbow as far as possible. Repeat the elbow flexion with the shoulder joint flexed 180 degrees. Is there any discomfort? Why should one expect the second task to be more difficult? What is the name for this phenomenon?
7. Flex the hip joint with the knee flexed. Flex the hip joint with the knee extended. Not the ROM of each of these movements. Why is there a difference? What is the name for this phenomenon?
8. Stand on one foot, and flex the hip and the knee of the free leg as far as possible. Stand on one foot, hyperextend the hip, and flex the knee as far as possible. Is there any difference in the two exercises? What is the difference called, and why would you expect a difference?
Questions 6, 7, and 8 above are based on passive and /or active insufficiency
of antagonistic groups of two-joint muscles. Specifics are as follows:
The performer should feel the stretch of the triceps when the elbow
is flexed and when the shoulder joint is fully flexed. The name for
this phenomenon is passive insufficency. The performer should feel
stretch in the hamstrings when the knee is extended and the hip is flexed.
The name for this phenomenon is passive insufficency. The performer
should be limited in range of motion when attempting to flex the knee fully
when the hip is hyperextended. The performer will feel extreme tightening
to cramping in the hamstrings. The name for this phenomenon is actiive
insufficiency.
9. If the muscle is the motive force for a segment's rotation, what type of muscle contraction is taking place?
In order for a muscle to cause movement in a body segment, the muscle must contract concentrically.
10. What type of muscular tension serves to stabilize a body segment to prevent it from moving under the influence of another force?
When stabilizing a body segment at a joint, a muscle contracts statically (isometrically).
11. If gravity is the motive force for vertebral flexion, what muscle group contracts to resist or control the speed of this movement, and what type of tension is this?
The vertebral column extensors would contract eccentrically to resist the accelerationdue to gravity. The instructor may wish to remind the students that if a segment is moving in the direction of gravity but faster than gravity would move that segment, then concentric muscular contaciton forces are being used (e.g., triceps for elbow extension in dribbling a basketball).
12. To which muscle group does a muscle belong if it can help produce wrist flexion? What is the name of the muscle group that can cause knee extension? hip abduction? shoulder transverse abduction? flexion of the vertebral column? medial roation of the hip?
If a muscle could help produce wrist flexion, it is a member of the wrist flexor muscle group (wrist flexors); knee extensors; hip abductors; shoulder transverse flexors; vertebral flexors; medial rotators of the hip.
13. To which muscle group does a muscle belong if it resists knee flexion? if it resist knee extension? if it resists ankle dorsiflexion? if it resists hip abduction? if it resists radioulnar supination?
If a muscle could resist a given joint movement, it is a member of
the muscle group that can cause the opposite joint movement:
- knee extensors can resist knee flexion; knee flexors can resist
knee extension; ankle plantar-flexors can resist ankle dorsi-flexion; hip
adductors can resist hip abduction; radio-ulnar pronators can resist radio-ulnar
supination.
14. Name some pairs of agonist-antagonist muscle groups acting across joints you select.
i. shoulder medial rotators and shoulder lateral
rotators
ii vertebral flexors and vertebral extensors
iii hip abductors and hip adductors
15. In Figure 2.5a-k, a person is performing a series of
exercies. For the initial movement and the return movement, identify:
a. each articulation where the movement is occuring,
b. each joint movement occurring,
c. the motive force causing each joint movement,
d. the resistive force acting against each joint movement occurring,
e. the functional muscle gruop used and the type of contraction used during
each joint movement, and
f. the body parts or joints needing stabilization during the whole excercise.
The following tables present the answers called for in each of the
eleven exercises illustratedin Figures 2-5a through k. Each exercise
incorporates two phases for each articulation examined; and some of the
exercies focus on more than one articulation.
Figure 2-5a
a.
vertebral column b.
flexion
b.
extension
c. gravity
c.
muscle
d. muscle
d.
gravity
e.
extensors
f.
lower body
Figure 2-5b
a.
Sternoclavicular joint
b. retraction
b.
protraction
d. gravity
c.
muscle
d. muscle
d.
gravity
e. protractors
e.
protractors
f. same
f.
wrist and lumbar vertbral column
a. shoulder
joint
b. transverse extension
b.
transverse flexion
c. gravity
c.
muscle
d. muscle
d.
gravity
e. transverse
e.
transverse flexors
f. same
f.
same
a. elbow
b. flexion
b.
extension
c. gravity
c.
muscle
d. muscle
d.
gravity
e. extensors
e.
extensors
f. same
f.
same
Figure 2-5c
a.
knee
b. flexion
b.
extension
c. gravity, weight machine
c.
muscle
d. muscle
d.
gravity
e. extensors
e.
extensors
f. same
Figure 2-5d
a.
sternoclavicular joint
b.
retraction
b. protraction
c.
muscle
c. gravity
d.
gravity
d. muscle
e.
retracotrs
e. retractors
f.
wrist, elbow, and vertebral column
a. shoulder
joint
b.
extension
b. flexion
c.
muscle
c. gravity
d.
gravity
d. muscle
e.
extensors
e. extensors
f.
same
f. same
--------------------------------------------------------------------------------------------------------------------------
Pages 71-72: Questions # 2 to 7 inclusive [answers in bold print]
2. List the ways in which a muscle may increase the total tension it can produce.
A muscle's total tension may be increased by increasing the number
of motor units being used, by increasing the stretch and frequency of electrical
impulses causing the contraction, increasing the length of the muscle,
and by synchronization of motor unit activity.
3. Identify the functional differences among SO,
FOG, and FG muscle fibers.
SO (slow twitch oxidative) fibers have a relatively small force of contraction, are very resistant to fatigue, and have a rich blood supply for aerobic endurance.
FOG (fast ixidative glycolytic)fibers are large, have a good blood supply for "medium" aerobic capacity; have better anaerobic capacity than SO fibers, and can contract faster.
FG (fast glycolytic) fibers have the strongest contractile force and a high anaerobic capacity; they are more fatigueable with a low aerobic capacity.
4. Speculate about the relative proportions of fiber types in the muscles of championship performers: (a) the legs of a marathon runner, (b) the arms of a shot-puter, (c) the arms of a gymnast, (d) the arms of a baseball pitcher, (e) the legs of a down-hill skier, (f) the legs of a cross-country skier, and (g) the legs of a mountain climber.
a. predominantly SO
b. predominantly FG
c. all three in about the same proportion
d. predominantly FOG and FG
e. predominantly SO with less FOG and FG
f. predominantly SO
g. predominantly SO with less FOG and FG
5. Explain how the elastic component in skeletal muscle is useful in movement.
A muscle's elastic component exerts a greater initial force on the segment as it recoils from a sudden forceful stretch. Continued recoil provides additional force as the muscle fibers shorten to move a segment fast. The elastic component also provides for smooth transition of the force of muscular applied to bone.
6. List and describe three activities inw hich the force-velocity relaionship of muscular contraction may be influential
The force on a handball is seemingly much less when hitting it from a back wall rebound, because the arm cannot move fast enough to accelerate the arm to match the speed of the ball moving in the same direction. The force applied to a tetherball when attempting to acccelerate it in its same movement direction. The force applied to the pedals on a fast-moving, low-geared bicycle will be limited due to the speed at which the legs must move.
7. Describe three activities in which the length-tension
relationship could influence performance.
Lengthening a muscle group prior to its concentric contraction provides
for a greater force of contraction. Fast-reversing backswing movements
also sue the elastic component ercoil for initial fast movement.
Examples of increasing muscle length for more force are; flexing the fingers
with the wrist hyperextended, extending the elbow with the shoulder in
flexion, extending the knee with the hip in extension, elevating the shoulder
girdle with the neck in flexion (all examples are of two-joint muscles
acting without suddent stretch.)
Chapter 2: continued - Neuromuscular Aspects of Movement [pp 64-76]
page 76 Questions 1, 2, 3 [answers in bold print]
1. Select a sports activity in which the extensor thrust reflex plays an imporant part, and describe how it does so.
In tennis, basketball, racquetball, and all other games innvoloving
quick footwork for stopping, starting and changing directions, the flexion
of one leg with the extension (thrust) of the other, pushing, leg allows
quick placement of the foot in the appropriate direction.
2. Describe how the Golgi tendon organs facilitate
and inhibit muscular contractions. Cite a sport-specific example.
When Golgi tendon organs are stretched, they will facilitate muscular contraction of their antagonist muscles and inhibit contraction of their host muscles. A sport-specific example would be performing stretching exercises using PNF method on the hamstrings. A second example would be the quick loss in arm wrestling once the arm begins to move in that direction.
3. Describe how the muscle spinles facilitate and inhibit muscular contractions. Cite a sport-specific example.
When muscle spindles are stretched, they will facilitate the contraction
of the host muscle and inhibit the antagonists. Since muscle spindles
are more sensitive to speed of stretch, any activity where forceful contraction
is needed would be enhanced by a fast stretch of those muscles prior to
use; for example, the backswing in tennis, racquetball, and handball strokes.