Table 2.

Correlations of standard time and frequency-domain HRV parameters with mean heart rate, age, body mass index, number of mild traumatic brain injury and weekly sport practice.

Standard HRV Parameter	Mean HR (bpm)		Age (months)		BMI (kg/m2)		n. mTBI		WSP
	R	P	R	P	R	P	R	P	R	P
SDNN (ms)	−0.48	<0.001	0.01	0.79	0.09	0.07	0.09	0.08	0.07	0.17
RMSSD (ms)	−0.64	<0.001	0.01	0.83	0.14	<0.01	0.05	0.32	0.07	0.18
pNN50 (%)	−0.67	<0.001	0.02	0.67	0.15	<0.001	0.06	0.27	0.07	0.18
FFT VLF (ms2)	−0.32	<0.001	0.07	0.16	0.09	0.10	0.08	0.13	0.08	0.14
FFT LF (ms2)	−0.30	<0.001	0.04	0.45	−0.01	0.85	0.09	0.09	0.06	0.24
FFT HF (ms2)	−0.70	<0.001	0.04	0.44	0.14	<0.01	0.04	0.44	0.07	0.19
FFT TP1 (ms2)	−0.61	<0.001	0.05	0.30	0.10	<0.05	0.07	0.21	0.08	0.10
FFT TP2 (ms2)	−0.61	<0.001	0.05	0.33	0.10	<0.05	0.07	0.20	0.08	0.12
FFT LF/HF	0.56	<0.001	0.01	0.99	−0.20	<0.001	0.01	0.86	−0.01	0.78
FFT nLF (nu)	0.56	<0.001	0.01	0.97	−0.20	<0.001	0.01	0.87	−0.01	0.78
FFT nHF (nu)	−0.56	<0.001	0.01	0.98	0.20	<0.001	−0.01	0.84	0.01	0.80
AR VLF (ms2)	−0.47	<0.001	0.07	0.18	0.07	0.17	0.10	<0.05	0.07	0.18
AR LF (ms2)	−0.25	<0.001	0.05	0.31	0.03	0.51	0.11	<0.04	0.10	0.06
AR HF (ms2)	−0.72	<0.001	0.03	0.55	0.15	<0.01	0.04	0.45	0.06	0.22
AR TP1 (ms2)	−0.63	<0.001	0.06	0.24	0.13	<0.05	0.08	0.15	0.10	0.06
AR TP2 (ms2)	−0.62	<0.001	0.06	0.27	0.13	<0.05	0.07	0.16	0.10	0.07
AR LF/HF	0.57	<0.001	0.02	0.67	−0.15	<0.01	0.05	0.36	0.03	0.56
AR nLF (nu)	0.57	<0.001	0.02	0.67	−0.14	<0.01	0.05	0.37	0.03	0.55
AR nHF (nu)	−0.57	<0.001	−0.02	0.67	0.15	<0.01	−0.05	0.36	−0.03	0.56

Mean HR, mean heart rate, BMI, body mass index, n.mTBI, number of mild traumatic brain injury and WSP, weekly sport practice. FFT denotes that a given HRV parameter was calculated by using Fast Fourier Transform, while AR indicates that the HRV spectrum was calculated with autoregressive method. R, Spearman's rank correlation coefficient. nu, normal units.