W5-L3: Muscle Variation

Question 1

Different muscle types?

Answer 1

Pennate muscles have an oblique fiber arrangement that increases the cross-sectional area and force production, but with a shorter range of motion.

Fusiform muscles have fibers running parallel to the muscle’s long axis, allowing for rapid shortening and high-velocity movements, but with lower force production.

Question 2

What is the Effect Of Pennation Angle?

Answer 2

The pennation angle affects a muscle’s force production and range of motion. A larger pennation angle increases the muscle’s cross-sectional area, enhancing its force-generating capacity, but results in a shorter range of motion and reduced shortening velocity.

Question 3

differentiate between the 2

Answer 3

Different Muscle Types:

1. Pennate Muscles:
   - Structure: Fibers are arranged obliquely to the muscle’s long axis.
   - Cross-Sectional Area (A): Increased due to the oblique fiber arrangement, allowing for more fibers in a given volume.
   - Advantages: Greater force production due to higher cross-sectional area.
   - Disadvantages: Shorter range of motion (ROM) compared to fusiform muscles.
2. Fusiform Muscles:
   - Structure: Fibers run parallel to the muscle’s long axis.
   - Fiber Length: Equal to muscle length, transmitting force directly to the tendon.
   - Advantages: Allows for rapid shortening and higher velocity movements.
   - Disadvantages: Lower force production compared to pennate muscles due to a smaller cross-sectional area.

Summary:
Pennate muscles have an oblique fiber arrangement that increases the cross-sectional area and force production, but with a shorter range of motion. Fusiform muscles have fibers running parallel to the muscle’s long axis, allowing for rapid shortening and high-velocity movements, but with lower force production.
§ Allows for rapid shortening

Question 4

Pennation in the vastus lateralis

Answer 4

Question 5

Fiber Length-Muscle Length Ratio

Answer 5

• Ratio of individual fiber length to muscle’s total length length (FL:ML) usually varies between 0.2 and 0.6
• Individual fibers in the longest muscles (e.g., such as the upper and lower limbs) remain significantly shorter than the muscle’s overall length.
• For relatively longer muscles, a given change in length results in the individual sarcomeres shortening less and less force being produced.

Question 6

Architectural Properties:
Lower Limb Muscles

Answer 6

Explanation:
Force Production: Muscles with a large PCSA (like the quadriceps and plantar flexors) generate more force due to greater number of muscle fibers
Velocity: Muscles with longer fibers (like the hamstrings and dorsiflexors) are capable of contracting at higher velocities because the fibers can shorten more rapidly and over a greater distance.
Optimal Sarcomere Length: The length-tension relationship indicates that muscles have an optimal length where they can generate maximum tension. Deviations from this length (either shorter or longer) result in reduced force production.
Summary:
Pennate Muscles (e.g., quadriceps, plantar flexors): Have short fibers and a large PCSA, leading to high force production but lower velocity and shorter optimal muscle length.
Fusiform Muscles (e.g., hamstrings, dorsiflexors): Have long fibers and smaller PCSA, allowing for rapid shortening and higher velocity but lower force production.

Question 7

Architectural Properties:
Lower Limb Muscles
Quads vs Hamstrings

Answer 7

know how differ
Quads - pennate
Hamstrings - fusiform

Question 8

What is the Strength Ratio between the Quads and Hams?

Answer 8

• Quad muscles exhibit a greater force capacity than hamstrings
• These design differences suggest susceptibility of the hamstrings to tear when an abrupt force output imbalance occurs during maximal activation between quads and hamstrings.
• Strength ratio typically computed by dividing the maximal flexor moment (or strength output) by the maximal extensor moment (i.e. H:Q)

Question 9

What is the strength ratio of quads to hamstrings?

Answer 9

• A ratio of 0.5 or 50% of hamstring strength to quadriceps is sufficient for daily living activities bur for athletic activity, the ratio required is closer to 0.8 or 80% muscle activity.
• From an ACL injury perspective, it is desirable to obtain a H/Q ratio closer to 100%- i.e. equal hamstring and quadriceps