# Stride Length Impacts on Sagittal Knee Biomechanics in Flat Ground Baseball Pitching
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & & **Peak Knee Height** & **Generation Phase** & **Stride Foot Contact** & **Brace- Transfer** & **Maximal External Rotation** & **Acceleration Phase** & **Ball Release** \\ \hline \multirow{3}{*}{Joint Angle (\({}^{\circ}\))} & OVER-STRIDE & \(-83.8\) & \(-61.1\)*\({}^{\dagger}\) & \(-46.8\) & \(-48.0\)***\({}^{\times 3}\) & \(-43.7\) & \(-40.2\)*\({}^{\times 3}\) & \(-37.4\) \\  & UNDER-STRIDE & \((26.6)\) & \((19.6)\) & \((12.0)\) & \((1.55)\) & \((12.4)\) & \((2.33)\) & \((13.3)\) \\  & UNDER-STRIDE & \(-89.1\) & \(-68.6\) & \(-52.9\) & \(-56.5\) & \(-49.6\) & \(-45.0\) & \(-41.2\) \\  & UNDER-STRIDE & \((29.8)\) & \((17.0)\) & \((12.4)\) & \((25.53)\) & \((10.6)\) & \((3.00)\) & \((11.6)\) \\ \hline \multirow{3}{*}{ \begin{tabular}{c} Angular \\ Velocity (\({}^{\circ}\)/s) \\ \end{tabular}  } & OVER-STRIDE & \(-37.4\) & \(38.8\) & \(-69.6\) & \(33.0\) & \(159.5\) & \(213.6\) & \(249.7\) \\  & UNDER-STRIDE & \((17.2)\) & \((77.6)\) & \((168.4)\) & \((66.3)\) & \((121.0)\) & \((35.8)\) & \((137.6)\) \\  & UNDER-STRIDE & \(-83.9\) & \(39.3\) & \(-83.7\) & \(10.9\) & \(188.1\) & \(218.8\) & \(241.2\) \\  & UNDER-STRIDE & \((13.1)\) & \((72.1)\) & \((98.2)\) & \((94.3)\) & \((96.6)\) & \((20.1)\) & \((114.3)\) \\ \hline \multirow{3}{*}{\ \begin{tabular}{c} Joint \\ Moments \\ (\%BW *H) \\ \end{tabular}  } & OVER-STRIDE & \(-5.65\) & \(-2.92\) & \(14.5\) & \(70.9\) & \(84.6\)*\({}^{\times 3}\) & \(69.9\)*\({}^{\times 3}\) & \(59.2\) \\  & UNDER-STRIDE & \((7.21)\) & \((5.89)\) & \((25.1)\) & \((24.9)\) & \((26.6)\) & \((8.72)\) & \((25.0)\) \\  & UNDER-STRIDE & \(-4.25\) & \(-2.52\) & \(12.3\) & \((77.4)\) & \(98.5\) & \(82.9\) & \(67.5\) \\  & UNDER-STRIDE & \((4.63)\) & \((4.95)\) & \((25.2)\) & \((33.1)\) & \((19.9)\) & \((11.2)\) & \((30.2)\) \\ \hline \multirow{3}{*}{ \begin{tabular}{c} Joint Power \\ (W/BW *H) \\ \end{tabular}  } & OVER-STRIDE & \(9.88\) & \(-1.86\)**hypothesis. The net internal knee joint moments and powers appeared to be sensitive to the two stride strategies along with different drive and stride knee angular dynamics, evident in the respective generation, brace-transfer, and acceleration phases (Tables 1 and 2). Our analysis focused solely on closed kinetic chain biomechanics, with the drive leg evaluated over the span of the entire pitching cycle whereas the stride leg (brace knee dynamics) commenced from the stride foot ground contact through to the ball release for both deliveries. Throughout the pitching cycle, both the drive and stride legs regulate the respective propulsion and bracing ground reaction forces [18]. Manipulating the stride length (25% under- and over-stride) led to a statistically different stride foot contact as well as duration of single and double supports during the generation and brace-transfer phases between the conditions [22]. This was concomitant with altered propulsive and bracing ground reaction forces [18], thereby affecting the drive and stride knee joint kinematics and kinetics. Longer strides reportedly prolonged the propulsive generation phase prior to stride foot contact (80% of the pitching cycle) whereas shorter strides saw the generation phase decrease to 73% of the pitching cycle [22], consequently altering the knee dynamics. Accordingly, a greater drive knee extensor effort in the propulsion (generation phase) with longer strides was substantiated, concomitant with greater stride knee extensor moments in bracing with reduced strides. The shorter strides delayed the drive leg knee extension mechanics, with associated increases in the stride knee joint powers in bracing during the acceleration phase of throwing. The longer strides evoked greater drive knee extension and joint power throughout the pitching cycle (maximizing propulsion), with a concomitant increase in the stride knee extension for effective bracing (Figure 1A). In contrast, shorter strides required less drive knee extensor effort, as evidenced by lower extensor knee moments during the generation phase to propel the body (Figure 1A).