Monitoring stress and allostatic load in first responders and tactical operators using heart rate variability: a systematic review

Table 2 HRV metrics following a singular stressor in comparison to baseline and stress time points

			HRV Metric
Immediately post compared to stress			Time Domain				Frequency Domain							Non-Linear
Study	Participant groups	n=	RRi	RMSSD	SDNN	PNN50	TP	VLF	LF	HF	LF n.u.	HF n.u.	LF/HF	SD1	SD2
Adams et al. [52]		12	↑		↑				↔	↑			↓
Clemente-Suárez et al. [23]		20	↑		↑
Giessing et al. [46]		19		↑
Hansen et al. [24]		53	↑*	↑
Hansen et al. [56]		65		↑
Mulder et al. [58]		48	↑*	↑
Saus et al. [59]		36		↑
Souza et al. [60]		50	↑	↑
Staller et al. [61]		25	↑*	↑
Strahler & Ziegert [62]		50	↔*	↔
Vigo et al. [65]		12	↑	↔	↑		↔†	↔† ↔%	↔† ↔%	↔† ↔%			↔
Immediately post compared to baseline
Adams et al. [52]		12	↑		↑				↔	↑			↓
Bustamante-Sánchez & Clemente-Suárez [69]		39	↔*	↓		↔					↔	↔
Clemente-Suárez et al. [23]		20	↓		↓
Delgado-Moreno et al. [70]		20	↓*						↑	↓
Delgado-Moreno et al. [71]		35		↓					↑	↓			↑
Duarte & Morgado [72]		20	↓								↑	↓	↑
Dussault et al. [30]	Short flight supine	7									↑	↓	↑
	Long flight supine	26					↔				↔	↔	↔
	Long flight standing	26	↔*	↑	↑	↔	↑				↓	↑	↓	↑	↑
Ghazali et al. [73]		48	↓			↓							↑
Giessing et al. [46]		19		↔
Hansen et al. [24]		53		↑
Marins et al. [74]		13		↓					↓	↓			↑
Mulder et al. [58]		48	↔*	↓
Sanchez-Molina et al. [75]		19	↓*	↓					↑	↓
Sanchez-Molina et al. [76]		19	↓*	↓					↑	↓
Saus et al. [59]		36		↔
Souza et al. [60]		50	↔	↔
Staller et al. [61]		25	↓*	↓
Strahler & Ziegert [62]		50	↓*	↓
Vigo et al. [65]		12	↑	↔	↓		↓†	↓† ↔%	↓† ↔%	↔† ↔%			↔

Participants included (n=), RRi R-R interval, RMSSD root mean square of successive differences, standard deviation of R-R intervals (SDNN), PNN50 percentage of R-R intervals greater than 50 ms, TP total power, VLF very low frequency power, LF low frequency power, HFhigh frequency power, LF n.u. low frequency normative units, HF n.u. high frequency normative units, LF/HF low frequency to high frequency ratio, SD1 standard deviation of the distance of data from the line of identity on a poincairé plot, standard deviation of the distance of data perpendicular to the line of identity at the average RRi length on a poincairé plot (SD2),derived from heart rate (*), natural log of variable (†), percentage of variable (%)

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