Effects of Ankle Dorsiflexion on Active and Passive Unilateral Straight Leg Raising RICHARD L. GAJDOSIK, BARNEY F. LEVEAU, and RICHARD W. BOHANNON The purpose of this study was to analyze the straight-leg-raising (SLR) maneuver while the ankle was fixed in dorsiflexion or relaxed in plantar flexion. Twenty-two healthy subjects underwent active and passive SLR with the ankle in each position. We used cinematography to document movement of the right lower limb and pelvis and electromyography to document hamstring muscle activity. Anal- yses of variance of the angles of maximum SLR and change in the pelvic position showed a significantzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA F ratio (p = .01) among the active and passive trials. Post hoc analyses demonstrated significant differences (p = .01) between SLR with dorsiflexion and SLR with plantar flexion. The EMG activity among trials was not significantly different. The possible causes of the effects of dorsiflexion on SLR are discussed. We encourage clinicians to document and compare SLR with dorsiflexion and SLR with plantar flexion, and we recommend additional research to examine the relative influence of tissue structures on SLR. Key Words: Exercise test, Leg, Muscles, Neurologic examination, Pelvis. The unilateral straight-leg-raising (SLR) test is widely reported in the lit- erature as an indirect test for measuring hamstring muscle tightness and as an aid in the diagnosis of sciatica and nerve root irritation. 1,2 Although interest in the SLR test has been widespread, a review of the literature revealed no stud- ies that examined the effects of ankle positions on SLR. Such studies are needed so that clinicians can have an objective understanding of the variables that may influence test results. Traditionally, when the SLR test is used to measure hamstring muscle tight- ness, the ankle is relaxed in plantar flex- ion (PF). No documentation exists, however, on the differences in SLR that may result if the ankle is held in dorsi- flexion (DF). If the position of the ankle influences measuring hamstring muscle tightness, as determined by SLR, then a standard ankle position should be re- quired for hamstring muscle tightness testing. When the SLR test is used in the diagnosis of sciatica or disk prolapse, passive DF of the ankle near the limit of pain-free SLR is used as a qualifying test because ankle DF puts tension on the sciatic nerve and its roots. 3-5 Studies of the movement of the sciatic nerve and its roots on SLR in cadavers have documented that movement of the nerve and roots diminishes progressively after 70 degrees of SLR, but tension generated along the nerve increases. 6, 7 The possibility that ankle DF could limit SLR seems reasonable in light of these reports. The purposes of our study were two- fold: 1) to analyze the effect of ankle DF on the angle of SLR in relation to the horizontal plane (SLR-horizontal), in relation to the pelvis (SLR-pelvis), and on the change in position of the pelvis in relation to the horizontal plane (pel- vis-horizontal) and 2) to examine the electromyographic activity of the ham- string muscles during both active and passive SLR. We expected to find a sig- nificant difference in the amount of SLR with the ankle fixed in DF in com- parison with the amount of SLR with the ankle relaxed in PF. We expected no difference in the EMG activity of the hamstring muscles. These expectations stemmed from our unpublished obser- vations that ankle DF limits both active and passive SLR in normal subjects and that the loss of motion is independent of the EMG activity of the hamstring muscles. METHOD Subjects Twenty-two healthy adults, 12 women and 10 men, with a mean and standard deviation for age, weight, and height of 28.0 ± 4.8 yr, 66.0 ± 9.9 kg, and 173.4 ± 8.0 cm, respectively, vol- unteered to participate in this study. Each subject reviewed and signed an informed consent form for the study, which was approved by the Committee on the Protection of the Rights of Hu- man Subjects of the University of North Carolina at Chapel Hill. Subjects had Normal muscle strength and range of motion of the back and lower extremi- ties and were not obese. They had no history of orthopedic or neurologic dis- orders. Mr. Gajdosik is Associate Professor, Physical Therapy Program, University of Montana, Mis- soula, MT, and currently a doctoral candidate, De- partment of Anatomy, School of Medicine, Univer- sity of North Carolina at Chapel Hill. Direct all correspondence to 612 Hibbard Dr, Chapel Hill, NC 27514 (USA). Dr. LeVeau is Professor and Chairman, Depart- ment of Physical Therapy, School of Allied Health Sciences, University of Texas, Health Sciences Cen- ter at Dallas, TX 75235. Mr. Bohannon is Chief of Physical Therapy, Southeastern Regional Rehabilitation Center, Cape Fear Valley Medical Center, PO Box 2000, Fayette- ville, NC 28302. This study was presented as a Research Platform Presentation at the Sixty-First Annual Conference of the American Physical Therapy Association, New Orleans, LA, June 19, 1985. This article was submitted November 7, 1984; was with the authors for revision four weeks; and was accepted April 30, 1985. 1478 PHYSICAL THERAPY