With regards to research that has been conducted on the use of MDT with headaches, one study compared mechanical traction, rhythmic impulse, and MDT exercises in relieving tension-type headaches (TTH). Mechanical cervical traction was found to be more effective at reducing headaches in both infrequent episodic and frequent episodic TTH. While MDT was used in this study, a general treatment was prescribed to each patient in that group without consideration to directional preference. This treatment had the patients perform the same exercises in the same progression, including four extension exercises, one flexion exercise, two lateral flexion exercise, and one rotation exercise. In addition, they performed the exercises for the same length of time for the same number of repetitions. The study was unclear about whether the exercises were administered by physical therapists or whether the practitioners were MDT credentialed.