Abstract
The objectiv e 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. Qualisys Gait Analysis System was used to analyze peaks and time parameters of GRFs in vertical (Fz), antero-posterior (Fy) and medio-lateral directions (Fx). The results showed that there were no significant differences between the non-pregnant and the pregnant women in the first peak (Fz1) (p=.147) and the second peak (Fz2) (p=.125) of vertical GRF, braking force (FyB) (p=.867) and propulsion force (FyP) (p=.929), as well as lateral (FxL) (p=0.994) and medial (FxM) GRF (p=.920). However, there was a significant increase in the Fz minimum (min) (p=.008), and a decrease in the difference between the Fz1 and Fz min (p=.042) and the difference between Fz2 and Fz min (p=.028). Moreover, there were increases in the time taken to reach the Fz1 (p=.024), Fz2 (p=.005), Fz min (=0.001), FyB (p=.010), FyP (p=.001), FxL (p=.010) and FxM (p=.011). These findings displayed that the pregnant women assumed a flatter pattern of vertical GRF and a decreased 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.