LAUSR

Background Muscle strain is a common injury with a high recurrence rate. Due to the heterogeneity of strain injuries, experimental animals provide controlled and reproducible models to investigate such injuries. Sciatic Function Index (SFI) is a clinically feasible method to assess hind limb recovery in rodents after induced injuries. Objectives To investigate time to recovery of SFI after induced-strain in tibialis anterior (TA) muscle in rats. Methods Sixteen adult male Wister rats were randomly and equally divided to a normal control group that received no intervention, and TA induced muscle strain group. Muscle strain was induced using an external weight that corresponded to 150% of the animal body weight. SFI was tested only once in the control group. For the muscle strain group, SFI was tested on the 1st, 2nd, 3rd, 4th, 7th, 11th, 20th and 24th days after strain induction. Results Comparisons between group showed significant difference in SFI on the 1st, 2nd, 3rd and 4th days (p= 0.012, 0.012, 0.012 and 0.028, respectively). Conclusions In a rat animal model of TA induced muscle strain, functional recovery measured by SFI is evident on the 7th day post-injury, which corresponds to the sub-acute phase of injury. Level of evidence V.