Question

Please answer the following questions to the best of your abilities. Write complete sentences to clearly communicate your ideas. Do not change the format of the document. Due to the school’s computer systems only Microsoft Word or PDF documents are accepted. Submit the completed assignment by uploading it to blackboard.

1. Explain the concept that muscles can enhance joint stability and at the same joint they can also create instability?

2. Which end of the muscle receives greater force when a muscle contracts? Why?

3. During which type of contraction is the greatest muscle force possible? Why?

4. Describe muscle fiber classification. Provide sample activities for each muscle fiber type.

Answer 1

1.

What Is Joint Instability?

Instability happens when tissues — such as muscles, ligaments, and bones — weaken. Once they are weak, they no longer hold the bones of the joint in proper place.Joints are flexible, allowing for movement. However, they also must be stable and strong.Strong ligaments hold the bones of joints in place while the joints are in motion and at rest. Muscles and tendons hold the bones of the joints in place most often when moving.

Types of joint instability

Common cases of joint instability occur in the:

• Ankle
• Big toe
• Elbow
• Hip
• Knee
• Neck
• Shoulder
• Thumb

What causes instability?

Risk factors that may cause joint instability include:

• Injury — such as a fall — can cause a dislocation of a joint or stretch or tear the ligaments.
• Overuse or repeating a movement over time can cause instability. Swimming, for example, can lead to shoulder instability.
• Multidirectional instability — known as being “double jointed” — happens to some people who are born with looser joints than most others.

Skeletal muscles maintain posture, stabilize bones and joints, control internal movement, and generate heat. Skeletal muscle fibers are long, multinucleated cells.Cartilage acts as a shock absorber to reduce friction. Ligaments help stabilize the joint, keeping it from moving outside of its intended range of motion. Tendons connect the skeletal system to the muscularsystem by attaching muscle to bone. When muscle contracts, the tendon acts on the bone, causing movement.

2.

When a muscle contracts, the actin is pulled along myosin toward the center of the sarcomere until the actin and myosin filaments are completely overlapped. In other words, for a muscle cell to contract, the sarcomere must shorten. However, thick and thin filaments—the components of sarcomeres—do not shorten.

3.

A muscle generates the greatest amount of force during fast eccentric (lengthening) contractions, followed by isometric contractions and slow concentric contractions. The least force is produced during fast concentric (shortening) contractions.An eccentric contraction is the motion of an active muscle while it is lengthening under load. Eccentrictraining is repetitively doing eccentric muscle contractions.

4.

For example, the human soleus leg muscle is predominantly type 1 fibers, whereas the triceps arm muscle is predominantly type 2