Monitoring one heart to help two: heart rate variability and resting heart rate using wearable technology in active women across the perinatal period

Table 4 Fixed effects parameter estimates from linear mixed models for resting heart rate (RHR, n = 18). Model 1: time only. Model 2: moderating effects of activity minutes per day. Model 3: moderating effects of moderate/vigorous activity minutes per day. Time was restricted to 43 weeks prior to birth and 8 weeks post-partum for the models

RHR Model	Independent Variable	Estimate	SE Estimate	Df	t-value	p-value
Model 1: Time only
	Intercept	74.43	1.91	17.2	38.91	< 0.0001
	Days until delivery
	−301 to −48 days	0.05	0.003	17.8	15.55	< 0.0001
	−49 days to 20 days pp	−0.22	0.01	4936	−44.19	< 0.0001
	21 days pp. to 56 days pp	0.06	0.02	4932	3.15	0.002
Model 2: Time plus moderating activity minutes
	Intercept	74.84	1.91	17.4	39.23	< 0.0001
	Activity minutes per day	−0.03	0.01	4923	−3.86	0.0001
	Days until delivery
	−301 to −48 days	0.05	0.003	19.4	15.84	< 0.0001
	−49 days to 20 days pp	−0.23	0.01	4933	−40.12	< 0.0001
	21 days pp. to 56 days pp	0.09	0.02	4926	3.88	0.0001
	Moderators
	Activity^a-301 to − 48 days	−0.0001	0.00004	4927	−2.79	0.005
	Activity^a-49 days to 20 days pp	0.001	0.0002	4918	2.93	0.003
	Activity^a21 days pp. to 56 days pp	−0.002	0.001	4918	−2.1	0.04
Model 3: Time plus moderating mod./vig. Minutes
	Intercept	74.60	1.91	17.4	39.04	< 0.0001
	Mod./vig. Minutes per day	−0.02	0.01	4923	−1.99	0.047
	Days until delivery
	−301 to −48 days	0.05	0.003	19.2	15.47	< 0.0001
	−49 days to 20 days pp	−0.23	0.01	4933	− 39.99	< 0.0001
	21 days pp. to 56 days pp	0.08	0.02	4926	3.46	0.0005
	Moderators
	Mod./vig. ^a-301 to −48 days	−0.0001	0.0001	4928	−1.25	0.21
	Mod./vig. ^a-49 days to 20 days pp	0.001	0.0003	4917	1.95	0.051
	Mod./vig. ^a21 days pp. to 56 days pp	−0.002	0.001	4917	−1.56	0.12

^aAbbreviations: RHR Resting heart rate, Mod/vig. Moderate-vigorous daily activity minutes, pp post-partum

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