Purpose: People with both pronated feet and anterior cruciate ligament repair may benefit from walking on sand as a therapeutic option. The consequences of walking on sand on the muscular activity and gait biomechanics of these people are not well understood. This study aims to determine how sand training affects gait mechanics in individuals with both anterior cruciate ligament repair and pronated foot.
Methods: The intervention and control groups included 28 adult males with pronated feet, where anterior cruciate ligament repair was randomly performed. The walking task was done on an 18-meter walkway at a consistent velocity. Muscle activities and ground reaction forces (GRF) were recorded using an electromyography system and a Bertec force plate, respectively. 
Results: Group-by-time interactions were significant for anterior and posterior reaction forces (P<0.019; d=0.49-0.66). Post hoc analysis demonstrated a significant increase for anterior and posterior reaction forces in control but not in the intervention groups. Also, group-by-time interactions were significant for vastus activities during heel contact (P=0.033; d=0.88). 
Conclusion: The results showed that vastus lateralis activity was higher in the intervention group during the heel contact than those of the control group.