Age-related changes in upper limb motion during typical development

Abstract

Background and aim: Understanding the maturation of upper limb (UL) movement characteristics in typically developing (TD) children is key to explore UL deficits in those with neurodevelopmental disorders. Three-dimensional motion analysis (3DMA) offers a reliable tool to comprehensively evaluate UL motion. However, studies thus far mainly focused on specific pre-defined parameters extracted from kinematic waveforms. Here, we investigated age-related differences in UL movement characteristics over the entire movement cycle in TD children.

Participants and methods: We assessed the non-dominant UL of 60 TD children (mean age 10y3m±3y1m) using 3DMA during eight tasks: reaching (forwards (RF), upwards (RU), sideways (RS)), reach-to-grasp (sphere (RGS), vertical cylinder (RGV)) and activities-of-daily-living mimicking tasks (hand-to-head (HTH), hand-to-mouth (HTM), hand-to-shoulder (HTS)). We investigated differences between four age-groups (5-7y, 8-10y, 11-12y, 13-15y) in: (1) spatiotemporal parameters (movement duration, peak velocity, time-to-peak velocity and trajectory straightness), and (2) 12 UL joint angles, using Statistical Parametric Mapping (SPM).

Results: We found that the 5-7y children moved with lower peak velocity and less straight trajectories compared to the 11-12y group (peak velocity: RS, HTS, p<0.01; trajectory: RU, RS, RGV, HTS, p<0.01) and the 13-15y group (peak velocity: RF, RS, RGS, RGV, HTH, HTS, p<0.01; trajectory, all tasks, p<0.01). The 5-7y children showed increased scapular protraction compared to older children (8-10y and 11-12y, HTS), as well as increased scapular medial rotation compared to the 13-15y group (RGS). During RU, the 5-7y children moved more towards the frontal plane (shoulder), unlike the 13-15y group. Lastly, the 5-7y group used less elbow flexion than older children (11-12y and 13-15y) during HTH and HTS.

Discussion and conclusion: In conclusion, our results point toward a maturation in UL movement characteristics up to age 11-12y, when UL motion seemed to reach a plateau. The reference values provided in this study will help to further optimize the interpretation of UL deficits in children with neurodevelopmental disorders.

Fig 1. Spatiotemporal parameters per age-group for eight UL tasks (reaching, left; reach to-grasp, middle; ADL-mimicking, right): (A) peak velocity, (B) trajectory straightness, (C) movement duration, and (D) time to peak velocity.

Data is shown as mean (standard deviation), except for trajectory straightness (median (first and third quartile)) RF, reaching forward; RU, reaching upwards; RS, reaching sideways; RGS, reach-to-grasp a sphere; RGV, reach-to-grasp a vertically oriented cylinder; HTH, hand-to-head; HTM, hand-to-mouth; HTS, hand-to-shoulder; y, years. Significant post-hoc differences (Bonferroni-Šidák correction α<0.0085) are shown as follows: Δ between 5-7y and 11-12y, § between 5-7y and 13-15y, and ¥ between 8-10y and 13-15y. Post-hoc analyses did not show significant differences for other between-group comparisons.

Fig 2. Upper limb joint kinematics for elbow flexion-extension during (A) HTH and (B) HTS, (C) scapula pro-retraction during HTS, and (D) shoulder elevation plane during RU.

Top panels represent mean and standard deviation per age-group: 5-7y (orange), 8-10y (blue), 11-12y (green) and 13-15y (yellow). Bottom panels show the one-way ANOVA Statistical Parametric Mapping (SPM) output: solid black line represents the statistical curve (i.e. F-curve), red dotted line represents the statistical threshold calculated with random field theory. Significant clusters identified by SPM are shown in grey, i.e. the area where the statistical curve crosses the statistical threshold. The black bars below each graph represent the summarized SPM{t} output of the post-hoc analyses, including information regarding pair-wise comparison, cluster location, and p-values.