Introduction: Ground reaction forces during walking and running reflect the distribution of pressure on the plantar surface of the foot. The distribution of plantar pressures is an important aspect of race walking. This study examined the pressure distribution differences in barefoot and shod conditions for elite Chinese race walkers during simulated race walking. Results will offer valuable insight into differences in barefoot and shod race walking conditions, and consequentially training techniques. Methods Seven elite Chinese race walkers were evaluated. Their mean age was 19.4 yr, and their weight range was 490-637 N. They had no history of health problems or foot and ankle injury. A footscan pressure plate (RS Scan International, 1m x 0.4m,8192 sensors, 500Hz) was mounted flush in the middle of a 12m long EVA walkway. Subjects were asked to walk barefoot and shod across the force plate. The pressure data was stored and analyzed using the Footscan 7 analysis system. For analysis of roll-off patterns and loading of the foot, the plantar surface of the foot was divided into ten functional areas: medial heel (H1), lateral heel (H2), midfoot, metatarsal heads - (M1, M2, M3, M4 and M5), hallux and the second to fifth toe area. Total foot contact time was divided into four phases: initial contact phase, forefoot contact phase, foot flat phase and forefoot push-off phase. Results / Discussion The results indicated that the plantar pressure over time curve was wave shaped, with two peaks and one valley. The highest pressures during race walking were exerted at the heel and were lowest during midfoot region contact; with the second peak during contact of the second and the third metatarsal heads. Force values for both peak and mean plantar pressures were greater when walking barefoot than in shoes. The ratio values of the peak pressures were 1.29:1. . The COP path gave information about stability under the foot and roll-off (Hallemans Et Al, 2003). At initial foot contact, the COP is found at the lateral heel (H2) followed by the medial heel (H1). During roll-off it moves laterally and then anteriorly. When the forefoot area is reached, it quickly shifts medially again, closely following the foot axis. Oscillations of the COP under the midfoot are uniform, and this indicates that the plantar flexor muscle controls COP oscillations properly. Poor uniformity of movement of the COP under the midfoot suggests poor coordination and stability of this region (Willems, 2004).] The second and third metatarsal heads (M2&M3) are major load carriers of the forefoot region. Relative vertical impulses indicate that load is primarily spread over the forefoot rather than the heel. During shod race walking, impulses were almost evenly distributed over different foot regions. The highest values were found under the forefoot (66.03%), followed by the rearfoot (21.68%), and midfoot (12.32%). Impulses were nearly absent under midfoot (5.4%) during barefoot race walking. This is mainly due to decreased peak pressures on the shoe heel and increased force on the midfoot region . The problem of selecting appropriate footwear for elite race walkers should not be ignored. Conclusions Findings mentioned above suggest that plantar pressure measurements are very suitable to reveal the dynamics of foot function. The curve of plantar pressure to time of race walking in barefoot and shod is a two-peak wave shape. The variation of COP has a uniform characteristic. The plantar flexor muscle controls COP oscillations properly. Relative vertical impulses indicate that load distribution is changed from shoe heel to mid foot while shod race walking.
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