The hip flexor muscles work together to bend the body at the hips. There are two primary hip flexors: the psoas major and iliacus. Because of their proximity to one another, their common insertion point on the femur, and the function they share in hip flexion, these muscles are commonly referred to as the iliopsoas. The rectus femoris, one of the quadriceps muscles on the front of the thigh, is also involved in hip flexion, albeit to a lesser degree. During the squat exercise, these muscles play a pivotal role in the execution of this move.
Flexion
Flexion can be described as decreasing the angle of a joint. If you stand erect with no bend in your body, the angle of your hip joint is said to be 180 degrees. Bending and lifting your knee will decrease the angle. The same applies if you bend forward at the hips. The farther you bend, the more you decrease the angle of the hip joint. This flexion of the hips occurs to initiate the movement required for the squat exercise.
Squats
The squat exercise can be executed in various ways. The different types of squats are barbell squats with the bar across your shoulders, dumbbell squats with one in each hand alongside the body, or body-weight squats that require no equipment. Body-weight squats can be done with your feet together, from a wide stance with toes pointing out or at any point in between. Weighted squats, however, are typically done with feet at least hip-width apart for balance and safety. You initiate the move by bending at the hips as if you are sitting down. Hip flexion is followed by knee flexion, which lowers the body to the floor. A squat to a position where the thighs are parallel with the floor is ideal.
Iliopsoas
During the squat, the function of the iliopsoas is to assist in flexing the trunk of the body forward. With their points of origin on the lumbar vertebrae and the ilium of the hip bone, respectively, the psoas major and the iliacus contract, or shorten, to create the movement. These muscles are not targeted for development in the squat, but they aid in its execution.
Considerations
When the upper body is in the upright position of the squat exercise, the psoas major aids in the stabilization of the spine. In this upright position, the psoas muscle works in conjunction with the opposing erector spinae, or extensor muscles, of the back region to keep the torso erect. It is during the upward phase of the squat that the iliopsoas muscles relax and the erector spinae muscles contract to return the upper body to an upright position.
References
- "Introduction to Sports Medicine and Athletic Training"; Robert C. France; 2004
- "Principles of Anatomy and Physiology, 12th Edition"; Gerard J. Tortora and Bryan Derrickson; 2009
- "Essentials of Personal Training"; National Strength and Conditioning Association; 2004
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