Impact of physical activity, sedentary behaviour and muscle strength on bone stiffness in 2–10-year-old children-cross-sectional results from the IDEFICS study

Table 2 Multivariate linear regression investigating the association of accelerometer-based PA data with SI, by age group

	Model 1			Model 2			Model 3^a			Model 4
	Adjusted for age, sex, country			Model 1 + adjusted for FFM, MDP, daylight duration			Model 2 + adjusted for either PA or/and sedentary time			Model 3 + adjusted for muscle strength
	β	p value	R² (%)	β	p value	R² (%)	β	p value	R² (%)	β	p value	R² (%)
Preschool children (N = 1512)
Sedentary time (hour/day)	−0.84	0.010	17.9	−0.73	0.008	18.6	−0.37	0.28	19.1
Light PA (hour/day)	0.11	0.77	17.5	−0.05	0.89	18.3	−0.47	0.26	18.6
Moderate PA (per 10 min/day)	0.76	<.001	18.1	0.83	<.001	19.0	0.75	0.003	19.1
Vigorous PA (per 10 min/day)	1.23	0.047	17.7	1.37	0.027	18.6	1.22	0.05	18.8
MVPA (per 10 min/day)	0.59	0.001	18.1	0.65	<.001	19.0	0.58	0.003	19.0
PA levels (per 100 cpm)	0.96	<.001	18.3	0.92	<.001	19.0
FFM (kg)^b	−0.41	<.001	17.9	−0.40	0.001	18.2	−0.40	<.001	19.0
School children (N = 2953)
Sedentary time (hour/day)	−0.60	<.001	24.1	−0.77	<.001	25.9	−0.42	0.015	27.0	−0.44	0.011	27.2
Light PA (hour/day)	0.26	0.17	23.8	0.43	0.025	25.5	0.004	0.98	25.9	0.09	0.69	26.3
Moderate PA (per 10 min/day)	0.81	<.001	24.8	0.94	<.001	26.7	0.83	<.001	26.8	0.78	<.001	27.1
Vigorous PA (per 10 min/day)	1.61	<.001	24.6	1.74	<.001	26.3	1.58	<.001	26.7	1.43	<.001	26.9
MVPA (per 10 min/day)	0.65	<.001	24.9	0.73	<.001	26.8	0.66	<.001	26.9	0.61	<.001	27.2
PA level (per 100 cpm)	0.84	<.001	24.7	1.02	<.001	26.7				0.96	<.001	27.0
FFM (kg)	0.44	<.001	25.3	0.45	<.001	25.3	0.50	<.001	26.7	0.41	<.001	27.0
Jumping distance (10 cm)	0.41	<.001	24.2	0.35	<.001	25.7	0.27	0.005	26.9
Handgrip strength (kg)^b	0.41	<.001	24.9	0.20	0.013	25.5	0.18	0.021	26.9

cpm average counts per minute, FFM fat-free-mass, MDP milk and dairy products, MVPA moderate-to-vigorous physical activity, PA physical activity
^aIn Model 3, the independent variables were (in addition to Model 2) adjusted as follows: sedentary time: moderate and vigorous PA; light PA, moderate PA, vigorous PA and MVPA: sedentary time; musculoskeletal fitness and FFM: PA level; PA level: no additional adjustment for other accelerometer-based variables
^bIn Model 2, FFM was adjusted for MDP and daylight duration

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