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

Table 1 Changes in HRV metrics from rest to stimulus in singular stressor

			HRV Metric
			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	↔		↔				↔	↔			↑
Brisinda et al. [28]		113	↓	↓	↓	↓	↓	↓ ↑%	↓ ↓%	↓ ↔%	↓	↑	↔	↓	↓
Clemente-Suárez et al. [53]		16	↔*	↓					↓	↓
Clemente-Suárez et al. [54]		38		↓							↑	↓
Clemente-Suárez et al. [23]		20	↓		↓
Diaz Manzano et al. [29]	High performance	10	↓*	↓		↓					↓	↑	↓	↓	↓
Diaz Manzano et al. [29]	Low performance	9	↓*	↓		↓					↔	↔	↔	↓	↓
Giessing et al. [46]		19		↓
Gnam et al. [55]		48	↓*	↓
Hansen et al. [24]		53	↔*	↔
Hansen et al. [56]		65		↓
Head et al. [5]		20			↓
Hourani et al. [57]		261							↓†	↔†
Mulder et al. [58]		48	↓*	↓
Saus et al. [59]		36		↓
Souza et al. [60]		50	↓	↓
Staller et al. [61]		25	↓*	↓
Strahler & Ziegert [62]		50	↓*	↓
Tornero-Aguilera & Clemente-Suárez [63]	SFV	16		↓					↑	↔
	SNFV	16		↔					↑	↔
	SNFNV	16		↓					↔	↔
	Control	16		↔					↑	↓
Tornero-Aguilera et al. [64]	Highly trained	18		↑							↑	↓
	Low trained	22		↑							↔	↔
	Control	9		↔							↔	↔
Vigo et al. [65]		12	↓	↔	↓		↓†		↓†	↓†	↔	↔	↔
Winslow et al. [66]		40			↓								↔

Participants included (n=), RRi R-R interval, RMSSD root mean square of successive differences, SDNN standard deviation of R-R intervals, PNN50 percentage of R-R intervals greater than 50 ms, TP total power, VLF very low frequency power, LF low frequency power, HF high 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, SD2 standard deviation of the distance of data perpendicular to the line of identity at the average RRi length on a poincairé plot,derived from heart rate (*), natural log of variable (†), percentage of variable (%), SFV soldier fire experience wearing night vision, SNFV soldiers no fire experience wearing night vision, SNFNV soldiers no fire experience not wearing night vision

ISSN: 1471-2458