Table 2.

Linear mixed model analyses of covariates on HRV.

	RMSSD (ln)
Fixed Effects	Estimates	95% CI	p
BMI	−0.06	−0.12 – −0.01	0.025*
Age	0.10	−0.11 – 0.30	0.356
Sex (girl)	−0.12	−1.76 – 1.52	0.231
MVPA	−1.23	−3.64 – 1.24	0.328
BMI × Sex	< −0.01	−0.10 – 0.10	0.999
Random Effects**
Between-Centre Variance	0.07
Residual Variance	0.28
N: Centres	11
N: Participants	146
N: Observations	142

Note: HRV, heart rate variability; BMI, body mass index; MVPA, moderate-vigorous physical activity; RMSSD, root mean square of successive differences; ln, natural logarhm; CI, confidence intervals

*p < 0.05

**Random effects are shown as estimates