Running with an exotendon reduces compressive knee contact force.

Running with an exotendon reduced peak knee compressive contact force by 8.4%.

• Reduction was 1.0 ± 0.7 BW (P = 0.026)
• Seven participants ran at 2.7 m/s with and without an exotendon
• Muscle-driven simulations of experimental data were used to compute contact forces
• The exotendon is a spring that couples the legs when attached to a runner's shoes

Lower quadriceps muscle forces were the primary contributor to the reduction in peak knee compressive contact force.

• Quadriceps muscles decreased their contribution to peak knee compressive contact force by 12.2%
• The reduction in quadriceps contribution was -0.8 ± 0.7 BW (P = 0.018)
• Muscle-driven simulations were used to decompose contributions to joint contact forces

Running with an exotendon produced no change in peak knee shear contact force.

• Both compressive and shear contact forces were computed at the knee
• Only the compressive component showed a statistically significant change
• Seven participants were included in the analysis

The exotendon produced no change in peak compressive or shear contact forces at the hip or ankle joints.

• Hip, knee, and ankle joint contact forces were all examined
• Neither compressive nor shear forces at the hip or ankle were significantly altered
• Simulations were run at 2.7 m/s for all participants

The exotendon was not originally designed to reduce joint forces but was found to reduce both energetic cost of running and compressive knee force.

• Prior work established that the exotendon reduces the energetic cost of running
• Effects on joint contact forces were previously unknown
• The current study highlights the ability of this simple device to make changes to gait that affect both energetic cost and compressive knee force