0 Stephens 2006 United States BACKGROUND AND PURPOSE: Passive stretching is widely used to increase muscle flexibility, but it has been shown that this process does not produce long-term changes in the viscoelastic properties of muscle as originally thought. The authors tested a method of lengthening hamstring muscles called "Awareness Through Movement" (ATM) that does not use passive stretching. SUBJECTS: Thirty-three subjects who were randomly assigned to ATM and control groups met the screening criteria and completed the intervention phase of the study. METHODS: The ATM group went through a process of learning complex active movements designed to increase length in the hamstring muscles. Hamstring muscle length was measured before and after intervention using the Active Knee Extension Test. RESULTS: The ATM group gained significantly more hamstring muscle length (+7.04 degrees ) compared with the control group (+1.15 degrees ). DISCUSSION AND CONCLUSION:: The results suggest that muscle length can be increased through a process of active movement that does not involve stretching. Further research is needed to investigate this finding. Stephens, J., Davidson, J., Derosa, J., Kriz, M., & Saltzman, N. (2006). Lengthening the hamstring muscles without stretching using "awareness through movement". Physical Therapy, 86(12), 1641-1650. http://www.hubmed.org/display.cgi?uids=17033041