When the muscle contracts and relaxes it goes through 2 phases of muscle motion: concentric and eccentric. Muscles go through these dynamic phases of movement in action around a joint. Select a joint in the human body and movement associated with that joint. In the movement you selected, what is the joint action, muscle action and link to a video of the movement itself.
Sample Solution
Joint: Elbow Joint
Movement: Bicep Curl
1. Joint Action:
- Flexion: The primary joint action during the upward phase of a bicep curl is elbow flexion. This is when the angle between the forearm and the upper arm decreases, bringing the hand closer to the shoulder.
- Extension: During the downward phase, the joint action is elbow extension. Here, the angle between the forearm and the upper arm increases as the weight is lowered.
2. Muscle Action:
For the bicep curl, the primary muscle involved is the biceps brachii.
Concentric Phase (Lifting the weight):
- Muscle Action: The biceps brachii undergoes a concentric contraction. This means the muscle shortens under tension, pulling the forearm towards the upper arm and causing elbow flexion. This is the lifting portion of the curl.
Eccentric Phase (Lowering the weight):
- Muscle Action: The biceps brachii undergoes an eccentric contraction. This means the muscle lengthens under tension, controlling the descent of the weight back to the starting position and resisting gravity. This controlled lengthening is crucial for muscle growth and injury prevention.Joint: Elbow Joint