Effects of infrapatellar straps on lower limb muscle synergies during running

Infrapatellar straps are commonly recommended for treating and preventing running-related knee injuries, and their effects have been investigated at the level of individual muscles. However, the use of straps may influence the neuromuscular control strategies of the knee, and the nervous system controls numerous muscles modularly through muscle synergy. This study aimed to investigate the effects of infrapatellar straps on muscle synergies during running. Kinematic, kinetic, and electromyography data from seventeen participants were recorded during running at self-selected speeds, both with and without infrapatellar straps. Muscle synergies were extracted from electromyography data using non-negative matrix factorization, including the number of modules, dynamic motor control index (DMC), muscle activation combinations, and temporal activation coefficients. Knee flexion angles and extension moments were estimated using OpenSim. Although wearing infrapatellar straps did not affect the number of modules or DMC, knee extensor weightings in the modules associated with the stance phase were reduced with the straps. Additionally, peak temporal activation in the propulsion phase was delayed when wearing the straps. Knee extension moments during the stance phase decreased significantly. While infrapatellar straps did not affect muscle synergy modularity, they altered activation patterns and weightings, suggesting that straps may help reduce quadriceps muscle forces.