Lower limb inter-joint coordination patterns are associated with walking experience in toddlers according to limb and stance periods.

Walking experience is crucial for inter-joint coordination during gait acquisition. Toddlers show asymmetrical lower limb function during early locomotion for transferring body weight (regulatory limb) and steering the direction of walking (impulse limb). This study aimed to investigate the association between coordination patterns and walking experience, and between coordination variability and walking experience according to healthy toddlers' lower limb function and stance periods. Typically developing toddlers (n = 22; 17.27 ± 3.13 months) were distributed into two groups: up to (LWE) and greater than (GWE) three months of walking experience. The lower limbs were classified as regulatory or impulse limb and analyzed during the onset (SO), mid (MS), and late (LS) stance intervals. Hip-ankle, knee-ankle, and hip-knee coupling angle (CA) and its variability (CAV) were assessed. A relationship was found between inter-joint coordination pattern and groups, which was distinct according to stance period and lower limb function: (a) hip-ankle CA: at SO for both limbs, MS for the regulatory limb, and LS for the impulse limb; (b) knee-ankle CA: at SO for both limbs and MS for the regulatory limb; (c) hip-knee CA: at SO for both limbs, at MS for the regulatory limb, and LS for the impulse limb. These findings were linked to differences observed in distal joints between groups, mainly at the ankle during stance onset. The CAV was negatively associated with walking experience only in the regulatory limb in the following variables: hip-ankle at MS, knee-ankle at SO, and hip-knee at LS. Findings showed different functional roles of the lower limbs in dealing with the demands of balance and propulsion during early walking.

Effects of additional load at different heights on gait initiation: A statistical parametric mapping of center of pressure and center of mass behavior.

The purpose of this study was to investigate the effects of different vertical positions of an asymmetrical load on the anticipatory postural adjustments phase of gait initiation. Sixty-eight college students (32 males, 36 females; age: 23.65 ± 3.21 years old; weight: 69.98 ± 8.15 kg; height: 1.74 ± 0.08 m) were enrolled in the study. Ground reaction forces and moments were collected using two force platforms. The participants completed three trials under each of the following random conditions: no-load (NL), waist uniformly distributed load (WUD), shoulder uniformly distributed load (SUD), waist stance foot load (WST), shoulder stance foot load (SST), waist swing foot load (WSW), and shoulder swing foot load (SSW). The paired Hotelling's T-square test was used to compare the experimental conditions. The center of pressure (COP) time series were significantly different for the SUD vs. NL, SST vs. NL, WST vs. NL, and WSW vs. NL comparisons. Significant differences in COP time series were observed for all comparisons between waist vs. shoulder conditions. Overall, these differences were greater when the load was positioned at the shoulders. For the center of mass (COM) time series, significant differences were found for the WUD vs. NL and WSW vs. NL conditions. However, no differences were observed with the load positioned at the shoulders. In conclusion, only asymmetrical loading at the waist produced significant differences, and the higher the extra load, the greater the effects on COP behavior. By contrast, only minor changes were observed in COM behavior, suggesting that the changes in COP (the controller) behavior are adjustments to maintain the COM (controlled object) unaltered.