Fitness Certifications »
Continuing Education »
Professional Resources »
About ACE »
ACE Store »
ACE Partner Account »
Need Help? Call Us » (888) 825‑3636
Follow ACE on

What is the Thomas Test?

What is the Thomas Test? | Mark Kelly | Exam Preparation Blog | 10/8/2012


Sign up to receive relevant, science-based health and fitness news from ACE each month.

The Thomas Test is a quick, simple assessment used to examine the length of the muscles involved in hip flexion. Assessing their length can help you determine the tightness of your client's primary hip flexor muscles, including the rectus femoris, illiopsoas and illiotibial (IT) band. There are a number of things to look at for each muscle group when assessing your client.

How Do You Administer the Thomas Test?

Begin the test by having your client sit on a bench or examination table and position themselves on their ischial tuberosity—the boney point we normally sit on. Take the client back so he or she is lying in the supine position with less than half of the thigh off the bench or table—the lumbar region of the back should be in contact with the bench. Have the client bring both knees toward the chest and then release one leg so it is extended and touches the bench or surface.

Thomas Test


If the client's lower leg touches the surface, he or she has good flexibility in the illiopsoas. If the back of the leg is even slightly off the surface, the individual has tight hip flexors. If the knee is bent 70 degrees or less, the rectus femoris (which crosses the hip and knee joint) is tight. Finally, if the leg abducts or is angled outward during the test, the IT band is tight.  

Mistakes to Avoid

There are several common mistakes to be aware of when administering the test, which could result in false positives or negatives. If the client is pulling his or her knee toward the chest too far and there is posterior tilt of the pelvis, it will be a false positive, making it appear that the illiopsoas is tight when it is not. Likewise, if the client is not pulling his or her knee back far enough or is lifting the lumbar back off the surface (lordosis) or creating a posterior pelvic tilt, it would be a false negative, appearing that the hip flexors are fine when they are actually tight.


A tight illiopsoas is common among individuals with sedentary lifestyles. Many people with tight hip flexors will have sore backs with excessive lordosis, and the Thomas Test can actually serve as a good stretch for the illiopsoas. Another good stretch is a modified low lunge—have the client perform an extended lunge with the back knee and shin touching the ground. Arching the back a small amount will add to the stretch, while bending at the waist will reduce it. Similar to the low lunge is the yoga position known as "pigeon pose," in which the front leg is turned outward with the lateral surface of the shin touching the ground.

The Thomas Test is a quick and easy way to test the flexibility of three critical muscles of the hip. Before assessing your client, be sure to ask if they have a sore or injured back. If they answer yes, do not have them perform this test.