The psoas is often used as shorthand for the iliopsoas muscle group, which is actually made up of three muscles: the psoas major, psoas minor, and iliacus. Collectively these muscles are commonly referred to as the hip flexors, although the term may also include other muscles that flex the hip, such as the tensor fasciae latae and the rectus femoris. Psoas stretches are exercises intended to increase flexibility to these muscles, which are located at the front of the hip and upper thigh, and they are recommended for anyone who spends much of his day in a seated position.
Since these muscles largely run vertically across the front of the hip, they become shortened when sitting. Sitting for long periods can result in psoas muscles that are chronically shortened and pull downward on the front of the pelvis in a standing position, resulting in a condition known as anterior pelvic tilt. Anterior pelvic tilt, which is identifiable by a slightly arched lower back, hips that jut backward, and a waistline that sits lower in the front than in the back, can contribute to low back and sciatic pain and weakened glutes and abdominals. Psoas stretches, therefore, can be an effective treatment for this muscle imbalance and its associated problems.
To stretch this muscle group, experts recommend a combination of active psoas stretches and foam-rolling technique, also known as self-myofascial release (SMR). SMR, which is a strategy used to release adhesions or knots in muscle tissue that may prevent proper lengthening, is often performed first. To employ SMR for the hip flexors, one would lie face down with his hip positioned over a foam roll, a dense cylinder of molded foam found in health clubs, physical therapy centers, and at fitness retailers. Using his body weight to apply pressure to the foam roll, he should slowly roll his hip back and forth over the roll, looking for any tender or painful spots. Once a spot is identified, one should hold his weight on that spot until the pain begins to diminish, typically after 30 seconds or so.
After performing SMR, active psoas stretches are recommended. Actively stretching the psoas involves contracting the glute muscles on the side being stretched while simultaneously lengthening the hip flexors. Fitness experts recommend the kneeling warrior stretch, in which the exerciser gets down on his left knee with the right knee bent 90 degrees in front of him and right foot planted on the floor. Contracting his glutes on the left side to tilt his pelvis under, he should then slowly push his hips forward on the left side while leaning back ever so slightly. The stretch should be held for 20-30 seconds without bouncing and then repeated on the other side.