Joint kinematics and ground reaction forces in overground versus treadmill graded running

Background: Treadmills are often used to assess running biomechanics, however the validity of applying results from treadmill graded running to overground graded running is currently unknown. Research question: The purpose of this study was to investigate whether treadmill and overground graded running have comparable kinematics and ground reaction force parameters. Methods: Eleven healthy male adults ran overground and on an instrumented treadmill as motion capture and force platform data were collected for the following conditions: downhill running at a slope of 128\ub0 at 10, 13 and 16 km c5h 121; level running at 10 and 13 km c5h 121; uphill running at a slope of +8\ub0 at 8, 10 and 13 km c5h 121. Sagittal joint angles at heel strike, mid-stance, and toe-off were computed for the ankle, knee and hip. Ground reaction force parameters including peak average and instantaneous normal loading rate, peak impact and active normal force, peak tangential (braking and propulsive) forces, and normal and tangential impulses were also calculated. Results: Joint kinematics and ground reaction forces for level running were generally similar between overground and treadmill conditions. The following variables were significantly higher during overground uphill running (mean difference \ub1 SD): average normal loading rate (14.4 \ub1 7.1 BW c5s 121), normal impulse (0.04 \ub1 0.02 BW c5s), propulsive impulse (0.04 \ub1 0.02 BW c5s), and vertical center of mass excursion (0.092 \ub1 0.031 m). The following variables were significantly higher during overground downhill running (mean difference \ub1 SD): ankle plantarflexion at toe-off ( 125.39 \ub1 6.19\ub0) and vertical center of mass excursion (0.046 \ub1 0.039 m). Significance: These findings suggest that subtle differences in kinematics and ground reaction forces exist between overground and treadmill graded running. These differences aside, we believe that overground kinematics and ground reaction forces in graded running are reasonably replicated on a treadmill

Regional plantar foot pressure distributions on high-heeled shoes-shank curve effects

Forefoot pain is common in high-heeled shoe wearers due to the high pressure caused by the center of body mass moving forward and the increased arch height with heel elevation. Sufficient arch support could reduce the high pressure over forefoot. However, too much arch support could lead to abnormal foot alignment and pain over midfoot. Little information is reported on the relationship among plantar arch height, shank curve design and plantar pressure. This study aimed at quantifying the plantar arch height changes at different heel heights and investigating the effect of shank curve on plantar pressure distribution. The plantar arch height increased to (7.6±1.3)mm at heel height of 75 mm. The Chinese standard suggests the depth of last should be 8.5mm for heel height of 75 mm. When a shank curve with higher depth of last (11 mm) was used, the peak pressure over forefoot further decreased in midstance phase, which might ease the forefoot problems, while the peak pressure over midfoot increased but not exceeded the discomfort pressure thresholds. To achieve a more ideal pressure distribution in high-heeled shoes, a higher than expected depth of last would be suggested that would not cause discomfort over midfoot