بررسی اثرات سن و سرعت راه‌رفتن بر نیروی عکس‌العمل عمودی زمین در جوانان و سالمندان

Objective Walking is one of the most important activities of daily living that plays a vital role in the lives of the elderly population and can help improve their physical and mental health. Especially, the survey of ground reaction force (GRF) during walking with different speeds between young and old adults results in better perception of essential mechanisms of speed regulation during walking. Thus, the purpose of this study was to examine the effects of age and walking speeds on vertical GRF in younger and older adults. Materials & Methods The subjects of this study included 15 younger and 15 older men with a mean age of 26.46 and 70.33 years, respectively. All the subjects were healthy and randomly selected. A-10-meters walking path was considered along the laboratory, and a three-axis Kistler Force plate was placed in the middle of the track. The distance of walking start line to force plate was 4 meters. Each subject walked this 10-meters path with self-selected (100%), slow (80%) and fast (120%) speeds. The vertical GRF during walking stance phases including weight acceptance or first peak phase (FZ1), midstance or depth phase (FZ2), and heel off or second peak phase (FZ3) were measured by the Force plate at 200-Hz frequency. The data were analyzed by ANOVA with repeated measures and Bonferroni tests. Results The results showed that the effects of age (P=0.002) and speed (P=0.001) on the mean vertical GRF are significant. Also, the interaction effect of age and speed on the mean vertical GRF was significant (P=0.013). According to the Bonferroni test, in both age groups, the mean vertical GRF was significantly different between different speeds (P<0.01). Moreover, at 100% (P=0.036) and 120% (P=0.002) speeds, there were significant differences between younger and older adults. At slow speed, there was no significant difference in GRF components (FZ1, FZ2, and FZ3) between the two age groups (p>0.05). At self-selected and fast speeds, there were significant differences in FZ1 and FZ3 between the two groups (p<0.01) while there was no significant difference regarding FZ2 (p>0.05). In addition, there were significant differences at FZ1 and FZ3 between different speeds (p<0.01). Conclusion In summary, the results of the present study showed that during walking with self-selected and fast speeds, the reaction forces of weight acceptance and heel off phases were significantly different between younger and older adults, but there was no significant difference in the reaction force of midstance phase. Moreover, in both age groups, there were significant differences among walking different speeds in the reaction forces of weight acceptance and heel off phases. It seems that lower extremity muscles strengthening in the older adults can increase walking speed and decrease falling risks and functional disabilities of these people.