Abdominal bracing changes lower quarter muscle activity but not reach distances during active forward reach on an unstable surface

Objective: This study examined the effects of abdominal bracing maneuver (ABM) performance on stable and unstable surfaces on active forward reach (AFR) distance as a measure of trunk control, measuring changes in reach distance and muscle activation patterns. Design: Single-group, repeated measures design. Methods: Twenty-eight subjects (mean age 25 ± 5.09 years) performed an AFR with and without ABM while on stable and unstable surfaces. Lower quarter muscle activity and forward reach distances were recorded. Results: Forward reach distances on the unstable surface were significantly decreased compared to the stable condition with and without ABM (p < .001). The surface-by-contraction interaction was significant for the tibialis anterior (TA) and gastrocnemius (GS). Significant main effects were found for internal oblique, external oblique, gluteus maximus, biceps femoris, TA, and GS, where muscle activity significantly increased during the ABM trials. The interaction between surface and contraction was significant for the TA and GS muscles. TA (p = .007) and GS (p < .001) activity increased with ABM on the unstable surface. TA activity increased with ABM on the stable surface (TA: p < .001). Conclusion: Reach distances decreased on the unstable surface, but ABM did not change reaching distance. Ankle muscle co-contraction occurred during ABM trials and posterior chain activity increased. These changes suggest ABM may be beneficial during forward reaching activities.