Questions: 2. Consider the following two scenarios - An individual attempts to lift a 25 lb weight in full elbow extension and is unable to move it. They then attempt to lift the same weight at 90 degrees of elbow flexion and they are able to move it. a. What type of contraction is occurring in scenario one (unable to move weight) and what forces are involved? b. What is one topic we've discussed in class that might explain why the individual is able to move the weight in the second scenario?

The question involves analyzing two scenarios where an individual attempts to lift a 25 lb weight under different conditions of elbow flexion. Let's address each part of the question step-by-step.

Answer: The type of contraction occurring in scenario one is an isometric contraction.

Explanation:

• Isometric Contraction: This type of muscle contraction occurs when the muscle generates force without changing its length. In this scenario, the individual is attempting to lift the weight but is unable to move it, meaning the muscle is exerting force but not shortening or lengthening.
• Forces Involved: The primary forces involved are the muscle force generated by the individual's muscles and the gravitational force acting on the 25 lb weight. The muscle force is not sufficient to overcome the gravitational force, resulting in no movement.

Answer: One topic that might explain why the individual is able to move the weight in the second scenario is the length-tension relationship of muscles.

Explanation:

• Length-Tension Relationship: This principle states that the force a muscle can generate is dependent on its length at the time of contraction. Muscles have an optimal length at which they can generate maximum force. When the elbow is at 90 degrees of flexion, the muscle length is likely closer to this optimal length, allowing the muscle to generate more force.
• In the first scenario (full elbow extension), the muscle may be either too stretched or too shortened, resulting in suboptimal force production. In the second scenario (90 degrees of elbow flexion), the muscle is at a more favorable length for generating force, enabling the individual to lift the weight.

• Scenario One: The individual experiences an isometric contraction because the muscle force is insufficient to lift the weight, resulting in no movement.
• Scenario Two: The individual is able to lift the weight due to the length-tension relationship, which allows the muscle to generate more force at 90 degrees of elbow flexion compared to full elbow extension.