👤 Maria Wilén

Muscular strength is a marker of current health and a predictor of long-term health outcomes in young populations, supporting the inclusion of muscle-strengthening activities into current guidelines and recommendations. Over the last decade, muscular strength has been included in several fitness-test batteries in children and adolescents. However, little is known about its relevance and the feasibility of assessing it in preschool children aged 3-5 years. Therefore, in this cross-sectional study, we aimed to generate reference values for handgrip strength in Swedish preschool children and to examine the associations of device-measured movement behaviours (sedentary time [ST], light physical activity [LPA], moderate-to-vigorous physical activity [MVPA], and sleep duration) with handgrip strength using compositional data analysis. A total of 3,218 preschool children (48.53% female) aged 3.0-5.5 years from Sweden were included. Handgrip strength was measured using a validated analog dynamometer following standardized procedures. Movement behaviours were assessed in a subsample of 2,328 children who had both handgrip data and valid accelerometer recordings. Compositional data analysis was used to examine associations between handgrip strength and the 24-hour time-use composition, adjusting for age, sex, body mass index, parental education, and wear time. Age- and sex-specific percentiles for handgrip strength were developed. Boys showed higher handgrip values than girls at all ages (e.g., median increased from 4.08 to 7.42 kg in boys and from 3.45 to 6.87 kg in girls between ages 3 and 5 years). When the proportion of time spent in MVPA increased relative to the other behaviours, handgrip strength rose by + 1.22 kg; the opposite was observed for ST, which related to - 0.84 kg lower handgrip strength. No significant associations were observed for LPA or sleep duration (LPA: β =-0.48 kg, 95% CI: -1.23, 0.27; sleep: β = 0.10 kg, 95% CI: -0.37, 0.57). This study provides the first normative reference values for handgrip strength from Northern Europe. These values offer a useful reference for screening and contextual interpretation of muscular strength in preschool children. Show less

The benefits of physical activity are well-documented, and healthy habits established in childhood often continue into adulthood. Recent research has shown that schoolyards provide a valuable platform for children to be physically active, with greener spaces in particular enhancing both physical and mental well-being. The City of Stockholm has formally decided to reconstruct 20 schoolyards, incorporating more play areas and greenery. This study will evaluate the impact of these reconstructions, aiming to increase physical activity levels among schoolchildren across all socioeconomic groups, while also contributing to climate change mitigation in urban environments. This study will utilize a stepped-wedge design, where each school undergoing schoolyard reconstruction will serve as both a control and intervention site. Over four years, from 2024 to 2027, five schools will have their schoolyards reconstructed each summer. Control data will be collected in the spring prior to the reconstruction, with follow-up data collected in the spring after the reconstruction. We aim to recruit 3 600 children aged 6 to 12 years. The primary outcome will be changes in physical activity, measured via accelerometers. Secondary outcomes will include changes in musculoskeletal fitness, perceptions of the schoolyard, and environmental impact. Given the 24-hour constraint of daily time, movement behaviors (e.g., MVPA, LPA, SB, and sleep) will be treated as compositional data. Log-ratio transformation will be applied and introduced as outcomes in general linear mixed models, with schools treated as random effects. This large-scale study has the potential to set new guidelines for physical health policies in schools across the City of Stockholm, potentially influencing the well-being of an even greater number of children. Additionally, the study could provide valuable insights into strategies for mitigating climate change through urban design, offering a model for sustainable school environments that promote both health and environmental resilience. The trial has been registered on ClinicalTrials.gov the 19th of May 2023, with the reference number NCT05865782. The online version contains supplementary material available at 10.1186/s12889-026-26609-9. Show less

Heparan sulfate (HS) proteoglycans influence embryonic development and adult physiology through interactions with protein ligands. The interactions depend on HS structure, which is determined largely during biosynthesis by Golgi enzymes. How biosynthesis is regulated is more or less unknown. During polymerization of the HS chain, carried out by a complex of the exostosin proteins EXT1 and EXT2, the first modification enzyme, glucosaminyl N-deacetylase/N-sulfotransferase (NDST), introduces N-sulfate groups into the growing polymer. Unexpectedly, we found that the level of expression of EXT1 and EXT2 affected the amount of NDST1 present in the cell, which, in turn, greatly influenced HS structure. Whereas overexpression of EXT2 in HEK 293 cells enhanced NDST1 expression, increased NDST1 N-glycosylation, and resulted in elevated HS sulfation, overexpression of EXT1 had opposite effects. Accordingly, heart tissue from transgenic mice overexpressing EXT2 showed increased NDST activity. Immunoprecipitaion experiments suggested an interaction between EXT2 and NDST1. We speculate that NDST1 competes with EXT1 for binding to EXT2. Increased NDST activity in fibroblasts with a gene trap mutation in EXT1 supports this notion. These results support a model in which the enzymes of HS biosynthesis form a complex, or a GAGosome. Show less

The exostosin (EXT) family of genes encodes glycosyltransferases involved in heparan sulfate biosynthesis. Five human members of this family have been cloned to date: EXT1, EXT2, EXTL1, EXTL2, and EXTL3. EXT1 and EXT2 are believed to form a Golgi-located hetero-oligomeric complex that catalyzes the chain elongation step in heparan sulfate biosynthesis, whereas the EXTL proteins exhibit overlapping glycosyl-transferase activities in vitro, so that it is not apparent what reactions they catalyze in vivo. We used gene-silencing strategies to investigate the roles of EXT1, EXT2, and EXTL3 in heparan sulfate chain elongation. Small interfering RNAs (siRNAs) directed against the human EXT1, EXT2, or EXTL3 mRNAs were introduced into human embryonic kidney 293 cells. Compared with cells transfected with control siRNA, those transfected with EXT1 or EXT2 siRNA synthesized shorter heparan sulfate chains, and those transfected with EXTL3 siRNA synthesized longer chains. We also generated human cell lines overexpressing the EXT proteins. Overexpression of EXT1 resulted in increased HS chain length, which was even more pronounced in cells coexpressing EXT2, whereas overexpression of EXT2 alone had no detectable effect on heparan sulfate chain elongation. Mutations in either EXT1 or EXT2 are associated with hereditary multiple exostoses, a human disorder characterized by the formation of cartilage-capped bony outgrowths at the epiphyseal growth plates. To further investigate the role of EXT2, we generated human cell lines overexpressing mutant EXT2. One of the mutations, EXT2-Y419X, resulted in a truncated protein. Interestingly, the capacity of wild type EXT2 to enhance HS chain length together with EXT1 was not shared by the EXT2-Y419X mutant. Show less