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Running is a very popular sport with millions of participants worldwide. As with any physical activity, injuries occur when the musculoskeletal system is overloaded. Running surfaces are often cited as a cause of injuries. The objective of this work was to determine changes in ground contact times, impulses, and shoe reaction forces while running on different surfaces. Eleven healthy adult males (22.9 ± 3.2 years, 176.9 ± 8.4 cm, 74.5 ± 8.6 kg) were recruited to run on four different surfaces: asphalt, concrete, grass, and a synthetic track. The majority of research on running surfaces has been completed in laboratory settings with force plates mounted beneath the running surfaces. Plantar pressure technology permits data collection on the actual running surfaces outside the laboratory. Therefore, data were collected at 250 Hz using a Parotec® plantar pressure measurement system. Participants ran at the same velocity on each of the surfaces. No significant differences were detected among the surfaces for shoe reaction forces, contact time, or impulse (P > 0.05). This implies that runners who choose to run on stiffer surfaces are not exposing themselves to additional risk as a result of loading but possibly because of internal compensatory mechanisms. However, these results may not apply to all runners.

The objective of this study was to determine if posture during gait can be affected by position of the load. It was hypothesized that the front pack would result in postural changes in the gait cycle, compared to a similarly loaded backpack. Thirteen healthy adults, free of any injury, volunteered to participate in this study. Two dimensional video data were collected at 50 Hz using a MacReflex video system. A backpack and a front pack were compared using loads of 10 and 15% of body weight. Markers were placed on the ear, acromion, greater trochanter and lateral joint line of the knee, lateral malleolus and fifth metatarsophalangeal joint. Data were collected while the participants walked at 0.75 stride/s. The data were used to calculate joint angles and displacements during each gait cycle. There was a significant difference noted in angles of the hip flexion, with the backpack condition demonstrating a greater flexion in each stride than either the control or front pack. Both backpack and front pack conditions demonstrated a significant change in neck motion compared to the control condition. The results of the position analysis over time also revealed an increase in the forward head position when participants were wearing the backpack compared to either the control or the front pack condition. It was concluded that the use of a front pack results in a more upright posture in gait, when compared to a backpack carrying the same load.