What are the major muscles of the upper body involved in flexion and extension?

The major muscles of the upper body involved in flexion and extension are primarily the biceps and triceps. The biceps brachii is responsible for the flexion movement at the elbow joint, which enables lifting or pulling actions, while the triceps brachii is involved in extension at the elbow joint, facilitating movements such as pushing.

Focusing on the biceps and triceps is crucial for understanding upper body mechanics. During exercises like bicep curls, the contraction of the biceps leads to elbow flexion, and during tricep extensions, the triceps contract to extend the elbow. This coordinated action between the two muscle groups allows for a full range of motion in various functional and athletic movements, making them essential for strength training and overall upper body fitness.

In contrast, the other options include muscle groups that are not primarily involved in upper body flexion and extension. The quadriceps and hamstrings are primarily lower body muscles, while deltoids are involved in shoulder movements, and latissimus dorsi mainly assists in shoulder extension and adduction rather than elbow movements.