The objective of the current study was to examine the effect of pregnancy during the 2nd and 3rd trimesters on ground reaction forces (GRFs). Twenty-four non-pregnant women and forty-eight pregnant women in the second and third trimesters participated in this cross-sectional study. Qualysis Gait Analysis System was used to analyze peaks and time parameters of GRFs in vertical (Fz), antero-posterior (Fx) and medio-lateral directions (Fy). The results showed that there were no significant differences between non-pregnant and pregnant women in the first peak (Fz1) (p=0.147) and second peak (Fz2) (p=0.125) of vertical GRF, braking force (FxB) (p=0.867) and propulsion force (FxP) (p=0.929), as well as lateral (FxL) (p=0.994) and medial (FxM) GRF (p=0.920). However, there was a significant decrease in the Fz minimum (min) (p=0.008), the difference between the Fz1 and Fz min (p=0.042) and the difference between Fz2 and Fz min (p=0.028). Moreover, there were increases in the time taken to reach the Fz1 (p=0.024), Fz2 (p=0.005), Fz min (p=0.001), FyB (p=0.010), FyP (p=0.001), FxL (p=0.010) and FxM (p=0.011). These findings displayed that the pregnant women assumed flatter pattern of vertical GRF and decreased upward and downward movement of center of gravity. This pattern may help to make the gait smooth and efficient. Increased time to reach peaks of GRFs may be a strategy to maximize balance during pregnancy.

中文翻译：

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妊娠中期和中期步行时地面反作用力的分析

当前研究的目的是检查妊娠第2和第3孕期对地面反作用力（GRF）的影响。妊娠中期和中期的24名非孕妇和48名孕妇参加了这项横断面研究。使用定量步态分析系统分析垂直方向（Fz），前后方向（Fx）和中外侧方向（Fy）的GRF的峰值和时间参数。结果表明，垂直GRF的第一个峰值（Fz1）（p = 0.147）和第二个峰值（Fz2）（p = 0.125），制动力（FxB）（p = 0.867）和推进力（FxP）（p = 0.929），以及外侧（FxL）（p = 0.994）和内侧（FxM）GRF（p = 0.920）。但是，Fz最小值（min）明显降低（p = 0.008），Fz1和Fz min之间的差异（p = 0.042）和Fz2和Fz min之间的差异（p = 0.028）。此外，到达Fz1（p = 0.024），Fz2（p = 0.005），Fz min（p = 0.001），FyB（p = 0.010），FyP（p = 0.001），FxL（ p = 0.010）和FxM（p = 0.011）。这些发现表明，孕妇假定GRF呈扁平状，重心向上和向下运动减小。这种模式可以帮助使步态平稳而有效。增加到达GRF高峰的时间可能是在怀孕期间最大化平衡的一种策略。这些发现表明，孕妇的GRF呈扁平状，重心向上和向下运动减小。这种模式可以帮助使步态平稳而有效。增加到达GRF高峰的时间可能是在怀孕期间最大化平衡的一种策略。这些发现表明，孕妇假定GRF呈扁平状，重心向上和向下运动减小。这种模式可以帮助使步态平稳而有效。增加到达GRF高峰的时间可能是在怀孕期间最大化平衡的一种策略。