Final Answer:
During the upward part of a bicep curl, the elbow joint movement is flexion, the muscle responsible is the biceps brachii, and the muscle action is concentric contraction.
Step-by-step explanation:
In the upward phase of a bicep curl, the primary movement at the elbow joint is flexion. This means that the angle between the forearm and the upper arm decreases as the hand is lifted towards the shoulder. The muscle responsible for this movement is the biceps brachii, located in the upper arm. The biceps brachii contracts concentrically during this phase, meaning that the muscle shortens as it generates force to lift the weight. Concentric contraction is the type of muscle action where the muscle actively contracts and produces force while overcoming resistance.
In summary, during the upward part of a bicep curl, the elbow undergoes flexion, the biceps brachii is responsible for this movement, and the muscle action is concentric contraction.