The hip flexors, in human anatomy, refer to a group of skeletal muscles that help pull the knee forward, flexing the femur, or femur, over the lumbo-pelvic complex. Together, called the iliopsoas, or the inner hip muscles, they are made up of the psoas major, the psoas minor, and the iliacus muscle. The hip flexor muscle group, located in the abdomen and thigh, is active when you rise from a sitting position, or when you dance, climb stairs, run, play soccer, or even do resistance training. Allowing for the up and down movements of your legs and at the same time working to balance the stability of your spine, they represent the strongest muscles in your body.
The problem, however, is that a sedentary lifestyle of sitting much of the time tends to allow the hip flexors to shorten, spreading problems from the back to the feet. Old age or sleeping in the fetal position will also speed up the shortening process of the flexors.
Lack of flexibility and not strength makes it difficult for the hip flexors to function properly. Imagine someone with a broken arm in a cast for 8 weeks. When the cast is removed, you will find that you cannot flex or stretch as usual. This is because your muscles, during this period of inactivity, have shortened and then many hours of physical therapy are needed before you regain your original flexibility. The same goes for your hips, and if you don’t flex them regularly, or if you force yourself to sit for long hours, you’re causing problems with your hip flexor muscles, limiting hip movement.
When the hip flexors lose their flexibility and become tight, the back is compressed by virtue of the forward thrust of the pelvis, and standing in this position requires an arch of the back. Experts commonly refer to this as a swayback and anatomically, as Hyperextension. Standing or sitting in this position for a long time puts pressure on the joints and lower spine, which in due time leads to painful arthritis.
To correct the situation, you can perform many exercises, but the most important is to warm up the flexors with moderate stretching, especially lunges, bending one knee in front and stretching the other leg behind. They also recommend using a 24-inch-long, 6-inch-diameter foam roller to roll between your knees and hips while lying on your stomach with your elbows for support.