The Use of Incline Treadmill Walking in the Rehabilitation of ACL Reconstructed Individuals

M.R. Torry, C.L. Eakin, R.A. Hintermeister, D.D. O’Connor, M.J. Decker, J.R. Steadman.

Steadman Philippon Research Institute, Vail, CO. Palo Alto Medical Foundation, Palo Alto, CA.

It has been stated that incline treadmill walking may be beneficial for the rehabilitation of ACL reconstructed (ACLr) patients. The purpose of this study was to compare the performance strategies of ACLr patients (bone-patella-bone; N = 12, 42 ± 4 days post-op.) with uninjured controls (N = 12) during incline treadmill walking (ITW) and to provide recommendations for the use of ITW in rehabilitating ACLr patients. For each subject, stance phase average EMG amplitude (AEMG) of the vastus medialis (VMO), vastus lateralis (VL), bicep femoris (BF) and medial hamstrings (MH) and lower limb kinematics were measured during 17 trials of walking at a self-selected speed and at six treadmill grades (0, 9, 12, 15, 18, 21%). Repeated measures ANOVA (p < 0.05) with Bonferonni post hoc analysis was used to detect between group by incline (p < 0.008) and within group by incline differences (p < 0.003). AEMG progressively increased from 0% to 21% incline in the ACLr group (VMO = 27%, VL = 19%, BF = 31%, MH = 32%) and in the uninjured group (VMO = 52%, VL = 50%, BF = 52%, MH = 31%). AEMG of the BF was significantly greater for the ACLr group at 0 and 9% inclines (p < 0.001). No other significant differences in AEMG activity existed between the groups at the six inclines. Knee angle at heel contact increased with incline in both groups. Knee angles at heel contact for the ACLr group were more flexed (5.1¡) than the uninjured group at 0% incline but less flexed than the uninjured group at all other inclines (mean difference = 8.1¡ ). Inclined treadmill walking may be beneficial for rehabilitating ACLr patients because it provides a functional activity that increases knee flexion and quadricep and hamstring AEMG activity during the stance phase. The increased knee flexion allows the hamstrings a better mechanical advantage to restrict anterior tibial displacement and protect the integrity of the joint capsule and ACL graft.