When you work with enough clients, eventually you notice all the variations in biomechanics and anatomy. You may or may not remember from your fitness professional certification studies that only about half of people have a psoas minor muscle. When it's there, it lies in front of the psoas major and originates from the sides of the 12th thoracic vertebra (T12), the first lumbar vertebra (L1) and the corresponding intervertebral disk (Farias et al. 2012).

It is a "weak trunk flexor" that, if present and strained, can reduce range of motion in the hip by as much as 50% (Healthline 2015). However, if you don't have a psoas minor, are you at a disadvantage?

"In almost 30 years I have not seen research or clinical indications that it matters," says Christina M. Christie, PT, president of Pelvic Solutions LLC, in Park Ridge, Illinois. "For the most part, the great majority of the population have tight hip flexors and a tight anterior chain, because we are a population that sits from the time we enter preschool. So no, it doesn't matter, because not one muscle in our bodies functions in isolation. The brain does not know muscles; the brain knows movement patterns."