Which muscle is primarily involved in knee raises?

The psoas major is primarily involved in knee raises because it plays a crucial role as a hip flexor. This muscle originates from the lumbar vertebrae and travels down to the femur, allowing for the flexion of the hip joint. When performing knee raises, the action involves lifting the thigh towards the abdomen, which requires active engagement of the hip flexors. The psoas major, along with the iliacus, works to facilitate this movement, making it the most significant muscle in performing knee raises.

The iliacus also contributes to hip flexion, but the psoas major is typically considered the primary muscle for this specific action due to its larger size and greater involvement in the flexion motion. The other muscles listed, such as the triceps brachii and brachialis, are primarily involved in elbow flexion and are not engaged during knee raising activities.