Upper extremity kinematics during walking gait changes through pregnancy.

BACKGROUND: Thirty percent of adults in the United States use wearable fitness devices as of 2020 [1], such as fitness watches, to monitor and track health and physical activity parameters. Physical changes during pregnancy may impact wrist worn device accuracy. The arms may be needed as compensation during walking because thorax axial rotation may be inhibited by pelvic tilt during pregnancy [2]. METHODS: To examine arm motion changes, twenty-three pregnant women (28 ± 4 y) were tested in four-week intervals ( ± 2 weeks) at 18-, 22-, 26-, 30- and 34-weeks' gestation. Kinematic data were measured during self-selected speed walking. Segment angles and angular velocities were analyzed over time. Linear regressions were used to analyze the correlations between arm motion and the other kinematic variables. RESULTS: Arm range of motion significantly increased (p = 0.006) over gestation, but leg, thorax, and pelvis range of motions did not significantly change. Arm range of motion was correlated with pelvis (r2 =0.311, p = 0.001, ß = 1.724) and leg (r2 = 0.285, p = 0.004, ß = 1.520) range of motion and gait velocity (r2 =0.566, p = 0.001, ß = 39.110). Arm velocities significantly increased (p < 0.012), as did leg velocities (p < 0.022) over gestation time, but thorax and pelvis rotational velocities did not significantly change over time. Arm velocity was correlated with leg velocity in both flexion (r2 =0.598, p = 0.001, ß = 1.61) and extension (r2 =0.568, p = 0.001, ß = 1.35). SIGNIFICANCE: Arm swing increases over the course of gestation during walking, which does not follow the exact pattern of changes seen in the legs, thorax, and pelvis. These results show that a typical gait analysis of lower body motions may miss important biomechanical changes or compensations at different points over pregnancy. Future studies should examine why these changes may occur. Studies should also be conducted to see if arm changes impact outcome parameters from fitness watches and affect their validity as an exercise tracker during pregnancy.

Stand-to-sit kinematic changes during pregnancy correspond with reduced sagittal plane hip motion.

BACKGROUND: The stand-to-sit motion has been linked to falls during pregnancy. It is also used in the clinical evaluation of functional performance. The physical and physiological changes during pregnancy may necessitate a change in stand-to-sit kinematic performance. Therefore, this study was conducted to evaluate the longitudinal changes to stand-to-sit kinematics during pregnancy. METHODS: Fifteen pregnant women were tested in 4-week intervals from 16 weeks to 36 weeks gestational age. They performed a 60-second trial of semi-continuous stand-to-sit motion. Sagittal plane motions at the ankle, knee, spine, and shoulders were measured. Additionally, three-dimensional hip motion was measured. Discrete variables (e.g. range of motion) and joint coordinations (through vector coding) were analyzed over time through a linear mixed model analysis. FINDINGS: The results indicate a shift away from sagittal hip motion throughout pregnancy. Hip range of motion and standing angle changed in favor of spine motion. Joint coordination shifted from hip dominant to spine- and shoulder-dominate coordination just before the start of sitting motion. Hip-knee joint coordination just before seat contact shifted from hip to a knee-dominant motion during pregnancy. INTERPRETATION: Discrete variable changes in the entire stand-to-sit motion seem to be driven by initial standing posture related to an increase in gestational lordosis. Likewise, standing joint coordination shift to upper body motion can be attributed to gestational lordosis limiting functional ability around the hip. The shift in motion away from the hip may provide insight into why both fall rates and low back pain rates increase during stand-to-sit during pregnancy.