A3) When lifting a load the large thigh muscles act most efficiently when the knee is bent…40 to 50 degrees30 to 40 degrees50 to 90 degrees30 to 60 degrees

To determine the optimal knee angle for lifting a load based on muscle efficiency, we can analyze the provided options in context to biomechanics and the effectiveness of muscle contractions.

Analysis of Options

1. 40 to 50 degrees: This range suggests a moderate knee flexion where the hamstrings are actively engaged, but it may not be optimal for maximal force production.

2. 30 to 40 degrees: This angle is relatively less bent, which may not activate the thigh muscles to their full potential for lifting heavier loads.

3. 50 to 90 degrees: This range indicates a significant knee bend. Typically, as the knee flexes more, the muscles can generate more force; however, beyond a certain point, muscle efficiency can decline due to mechanical disadvantages.

4. 30 to 60 degrees: This option covers a broader range of knee angles, allowing for engagement of different muscle groups including quadriceps and hamstrings, potentially leading to more efficient lifting mechanics across varying loads.

Conclusion

The most appropriate range for efficient muscle action is typically in the middle to deeper knee flexion, allowing the larger thigh muscles to operate effectively.

Final Answer

The most efficient knee bending for lifting a load typically occurs between 50 to 90 degrees.