A comparison and update of direct kinematic-kinetic models of leg stiffness in human running

Running in highly cushioned shoes increases leg stiffness and amplifies impact loading

“…Although, previous literature 29 , 30 indicate a very good agreement in the CoM movement obtained using the 3D approach and the force plate method, no studies have compared the results of these two techniques when running in shoes with different cushioning properties. Finally, of note is that although our leg stiffness values are well in line with other studies 26 , 30 , 31 using the direct 3D method, they are generally 25–55% greater than those 21 – 23 , 32 calculated with a traditional spring-mass model 19 , 20 . This discrepancy arises primarily from a much lesser leg compression values in studies using the direct 3D method (~7–9 cm) versus those using a traditional spring-mass model (~12–14 cm) rather than differences in the GRF.…”

“…Using a spring-mass model 26 , we determined the stiffness of the runner’s leg during the ground contact when wearing MAX shoes and CON shoes. The results revealed a significant main effect ( p = 0.007) for shoe conditions, showing greater leg stiffness for the subjects running with MAX shoes (Fig.…”

“…Leg compression in this study was determined directly from 3D motion analysis data as a distance vector between the proximal and distal end-points of the leg-spring 26 , 30 rather than using a traditional spring-mass model 19 , 20 . The hip joint centre was used as a proximal end-point, but unlike earlier studies 26 , 30 (with the direct 3D method) that used the centre of pressure location as a distal end-point, we selected the ankle joint centre for a distal end-point. This excludes any effect of possible shoe midsole deformation on leg compression values.…”

“…Leg stiffness ( k leg ) was then calculated by taking the ratio of the leg vector projected ground reaction force (GRF proj ) to the compression of the leg at the instant when this compression was maximal 26 : …”

Effects of Stride Length on Lower Limb Stiffness when Running with Body Borne Load

“…Leg stiffness (Kl) was calculated at the frame where leg length reached its minimum, and defined as the component of GRF directed from the center of pressure (CoP) to the hip joint center (Fe) divided by the change in leg length (Le) 73 . Leg length was defined as the linear distance between the CoP and the hip joint center 74 . Joint stiffness (Ktors) at the hip, knee, and ankle was calculated and defined as the difference between the maximum and minimum joint moment divided by the corresponding change in joint angle 25 .…”