@Article{Guo2026,
journal="Biology of Sport",
issn="0860-021X",
year="2026",
title="Weekday-specific associations of movement behaviors with body composition in preschool children: A compositional data analysis",
abstract="This study aimed to examine the differences in associations between 24-hour movement behaviors and body composition on weekdays versus weekends in preschool children, and to estimate the potential effects of	time	reallocation	among	behaviors	on	body	composition.	A cross-sectional	study	was	conducted	among	healthy	children	aged	3–6 years	recruited	from	urban	and	suburban	kindergartens	in	Beijing.	Movement	behaviors	were measured objectively using accelerometers on both weekdays and weekends, ensuring comparable assessment across contexts, sleep duration was obtained from parent-completed questionnaires. Body composition was assessed using bioelectrical impedance analysis. Compositional data analysis was applied to build multivariate regression models examining weekday and weekend movement behaviors independently. Isotemporal substitution analysis was used to predict changes in body composition under different time-reallocation among behaviors. Moderate-to-vigorous	physical	activity	(MVPA)	on	weekdays	was	significantly	associated	with	lower	percent	body	fat	(PBF)	and	higher	skeletal	muscle	mass	index	(SMMI),	while	sedentary	behavior	(SB)	was	correlated	with	lower	soft	lean	mass	index	(SLMI),	fat-free	mass	index	(FFMI),	and	SMMI.	Compositional	isotemporal	substitution	analysis	indicated	that	on	weekdays,	reallocating	5–30 minutes	from	SB	to	MVPA	was	associated	with	reduced	PBF	and	higher	muscle-related	indices,	whereas	reallocating	time	from	MVPA	to	SB	resulted	in	adverse	effects	on	these	metrics,	demonstrating	an	asymmetric	pattern.	No	significant	associations	were	observed	between movement behaviors and body composition on weekends. The findings indicate that the association	between	MVPA	and	favorable	body	composition	in	preschoolers	is	significant	on	weekdays	but	not	weekends, highlighting the context-dependent nature of movement behaviors in relation to body composition.",
author="Guo, Jin
and Liu, Xiangli
and Zhang, Haowen
and Wang, Chaonan
and Wang, Fang
and Chen, Wei
and Heng, Di
and Dong, Qingfeng
and Bao, Yihua
and Lu, Zhaoxu
and Zhang, Ting",
pages="1315--1327",
doi="10.5114/biolsport.2026.159563",
url="http://dx.doi.org/10.5114/biolsport.2026.159563"
}