Medial and Lateral Hamstring Muscle Activity Differs for ACL Graft Types

Objectives: The hamstrings are anterior cruciate ligament (ACL) agonists, with the semitendinosus and gracilis (ST/G) assisting the ACL by limiting excessive external rotation. Use of ST/G autografts is common in ACL reconstruction (ACLR). Regrowth of these tendons over the 1st post-operative year has also been reported. Little is known, however, regarding hamstring muscle activity over this period. The purpose of this study was to examine medial (MH) and lateral hamstring (LH) muscle activity during gait in athletes with different graft types one year after ACLR. Methods: Athletes who participated in cutting and pivoting sports before ACLR were tested one year after ACLR; 18 with ST/G (HS) autografts, 5 with bone-patella-tendon-bone (BPTB) autografts, and 12 with allografts (Allo). EMG electrodes were secured on the MH and LH. Athletes performed maximal voluntary isometric contractions for EMG normalization purposes followed by walking at a self-selected speed. Filtered EMG data were normalized to maximum muscle activity and mean activity was calculated for weight acceptance and the mid-to-terminal phases of swing. A repeated measures ANOVA was used to assess differences in MH and LH muscle activity between limbs in athletes with different graft types. Post-hoc one way ANOVAs and t-tests were used to further elucidate differences (p≤0.05). Results: During weight acceptance, there was a limb x graft (p