Inter-regional differences in body proportions in Indian children and adolescents-a cross-sectional multicentric study

Design and validation of a pediatric gait assistance exoskeleton system with fast non-singular terminal sliding mode controller

Existing exoskeletons for pediatric gait assistance have limitations in anthropometric design, structure weight, cost, user safety features, and adaptability to diverse users. Additionally, creating precise models for pediatric rehabilitation is difficult because the rapid anthropometric changes in children result in unknown model parameters. Furthermore, external disruptions, like unpredictable movements and involuntary muscle contractions, add complexity to the control schemes that need to be managed. To overcome these limitations, this study aims to develop an affordable stand-aided lower-limb exoskeleton specifically for pediatric subjects (8-12 years, 25-40 kg, 128-132 cm) in passive-assist mode. The authors modified a previously developed model (LLESv1) for improved rigidity, reduced mass, simplified motor arrangement, variable waist size, and enhanced mobility. A computer-aided design of the new exoskeleton system (LLESv2) is presented. The developed prototype of the exoskeleton appended with a pediatric subject (age: 12 years old, body mass: 40 kg, body height: 132 cm) is presented with real-time hardware architecture. Thereafter, an improved fast non-singular terminal sliding mode (IFNSTSM) control scheme is proposed, incorporating a double exponential reaching law for expedited error convergence and enhanced stability. The Lyapunov stability warrants the control system's performance despite uncertainties and disturbances. In contrast to fast non-singular terminal sliding mode (FNSTSM) control and time-scaling sliding mode (TSSM) control, experimental validation demonstrates the effectiveness of IFNSTSM control by a respective average of 5.39% and 42.1% in tracking desired joint trajectories with minimal and rapid finite time converging errors. Moreover, the exoskeleton with the proposed IFNSTSM control requires significantly lesser control efforts than the exoskeleton using contrast FNSTSM control. The Bland-Altman analysis indicates that although there is a minimal mean difference in variables when employing FNSTSM and IFNSTSM controllers, the latter exhibits significant performance variations as the mean of variables changes. This research contributes to affordable and effective pediatric gait assistance, improving rehabilitation outcomes and enhancing mobility support.

Variation of the cormic index since the onset of summer school camps in Spain (1887) up to present days

OBJECTIVES

To assess a secular change in proportion between lower limbs and torso, we analyzed the evolution of cormic index in schoolchildren attending summer camps organized by the Spanish National Pedagogic Museum between 1887 and 1924, also comparing to later studies up to the present.

SUBJECTS AND METHODS

Unpublished primary data for height and sitting height were collected from 805 individuals of both sexes. Data were pooled in cohorts according to age and year of measurement. Additionally, the analysis included comparison with published data from both national and international populations.

RESULTS

Among males, a noteworthy decrease of the cormic index is perceived from the first to the last camps, while in females this is only seen for the group under 11 years old. With data from published Spanish references (1900-2019) a decrease is observed for the male series but is not evident for females. Cormic index values from the camps overlap among the international references, despite the former being from much earlier years.

CONCLUSION

The cormic index decreased among Spanish male children along the decades.