Daily Limb Loading During Weightbearing Activities Following ACL Reconstruction Does Not Reflect Laboratory Gait

Previous work found that limb loading asymmetries during a sit to stand task assessed in lab testing related to asymmetries measured in daily activities in individuals 3-4 months post-ACL reconstruction (ACLr). However, it is not known how gait assessments in the lab relate to daily loading behaviors. This is important as gait composes the majority of loading activities performed throughout the day. PURPOSE: To determine the difference between limb loading symmetries (LLS) during lab-based gait and daily activities in individuals post-ACLr. METHODS: Thirteen individuals post-ACLr (7F; 115 ± 15 days post-ACLr; age: 26.7 ± 11.4 yrs) and 13 matched controls (CTRL; 7 F; age: 27 ± 11.1 yrs) performed four gait trials at self-selected speed over embedded force plates (1000 Hz) in a lab setting. Participants then wore pressure insoles (Moticon; 25 Hz) for nine hours a day for two days during daily activities. Limb loading impulse was calculated from vertical ground reaction force during stance in lab assessments (vGRF-lab) and vertical force during daily weightbearing activities (vF-daily) as the area under the force time curves. Weightbearing activities was defined as when combined limb vF-daily was greater than 50% bodyweight. Limb loading symmetry (LLS) was calculated as surgical/non-surgical impulse for vGRF-lab and vF-daily. A 2 x 2 ANOVA was performed to assess the effects of group (ACLr and CTRL) and environment (lab and daily) on LLS. RESULTS: There were significant main effects (group and environment: P < 0.001) and an interaction of group and environment (P < 0.001). LLS vGRF-lab did not differ between groups (ACLr 0.96 ± 0.04, CTRL 1.0 ± 0.02; P = 0.08). The ACLr group was more asymmetrical in daily activities than CTRL (LLS vF-daily: ACLr 0.77 ± 0.10, CTRL 0.96 ± 0.08; P < 0.001). ACLr group had greater asymmetry in the daily compared to lab environment (P < 0.001); no difference was observed in CTRL (P = 0.11). CONCLUSION: LLS characterized during lab gait did not translate to an ecological environment. When compared to controls, the ACLr group had similar LLS in lab. A 20% decrease in LLS was observed in the ACLr group across daily activities with no difference across environments in controls. These differences suggest that lab assessment may not capture gait behaviors practiced throughout the day in individuals post-ACLr.