We examined the effects of active and passive stretching
in a relatively young sample of patients with low back
pain and lower-extremity injuries, and the ability to
generalize our results is limited. Older patient populations,
patients with primary hip disorders, and other
patients with muscle tightness other than hip flexor
tightness may not respond as favorably. In addition, the
effects of passive and active stretching beyond 6 weeks
are unknown. We were unable to locate studies describing
the long-term maintenance of muscle length
changes using a stretching force