Effect of Different Soft Knee Braces on Quadriceps and Hamstring Activity During Running

Knee pain is a common running injury, and is associated with high and repetitive quadriceps contractions. Soft knee braces are commonly recommended for the prevention and management of this injury. However, the specific effect of soft knee braces on quadriceps muscle forces during running remains unclear. In addition, as the antagonistic muscle of quadriceps, few studies have explored whether the hamstring forces will change with the quadriceps forces when wearing soft knee braces. This study aimed to investigate the effect of two kinds of soft knee braces on quadriceps and hamstring muscle forces. OpenSim was used to calculate five healthy subjects' quadriceps forces, knee flexion angles, extension moments, and hamstring forces during running at self-selected speeds under three conditions: no knee brace (NKB), dual knee strap (DKS), and wrap-around knee brace (WAKB) after kinematics data and ground reaction forces were collected. The peak quadriceps forces decreased significantly in the DKS and WAKB conditions than that in NKB condition (p = 0.008 and 0.003, respectively). Maximum knee extension moments generated by the rectus femoris were significantly lower in WAKB condition than that in the NKB and DKS conditions (p = 0.004 and 0.015, respectively). Moments generated by the vastus lateralis was significantly lower in DKS condition than that in the NKB condition (p = 0.033). No significant differences were observed in knee flexion angles or hamstring forces. These findings indicate that soft knee braces can reduce quadriceps forces and knee extension moments, which may help relieve knee pain during running. Furthermore, different constraint strategies of braces affect specific quadriceps heads, implying that selecting knee braces based on individual muscle characteristics may produce better outcomes.