Which posture is associated with recruitment of lumbar and posterior thigh muscles?

The forward leaning posture is indeed associated with the recruitment of lumbar and posterior thigh muscles. This posture occurs when an individual leans forward from the hips, which increases the demand on the lumbar muscles as they work to stabilize the spine and maintain balance in this position. It also engages the posterior thigh muscles, such as the hamstrings, because these muscles aid in supporting the body and controlling movements when forward bending.

In contrast, a neutral posture typically promotes a more balanced alignment where the lumbar spine and other muscles are in a resting position. A backward leaning posture tends to shift the body's weight towards the back, which minimizes the engagement of the lumbar and posterior thigh muscles. Sitting posture, similarly, generally reduces the need for these muscles to work actively in comparison to the dynamic stabilization required in a forward leaning stance.