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. 2021 Apr 23;12:657274. doi: 10.3389/fphys.2021.657274

Table 3.

Characteristics of the studies included.

Author, year Participants [sample size, age (year), gender] HRV protocol (method, respiration, position) HR- and HRV-parameters Cardiovascular health and risk factors Recording length Intervention (type, duration, sessions/week) Control group
Badrov et al., 2013 32 (IHG3: 12; IHG5: 11; CG: 9)
Age: IHG3: 23 ± 4; IHG5: 27 ± 6; CG: 24 ± 8
100% female
1-lead ECG
Spontaneous
Supine
1.000 Hz
RHR, SDNN, RMSSD, pNN50, LF (ln, ms2), HF (ln, ms2), LF nu, HF nu, TP (ln, ms2), LF/HF, SampEn, α1 BP 10 min (256 beats for analysis) Isometric handgrip training
8 weeks
IHG3: 3, IHG5: 5 sessions
Yes
Bond et al., 2009 32 (TG: 16; CG: 16)
Age: TG: 20.4 ± 1.9; CG: 22.4 ± 2.2
100% male
2-lead ECG
6 breaths/min
n.r.
500 Hz
RHR, HF nu SBP, VO2 peak 5 min Endurance (bicycle)
8 weeks
3 sessions
Yes
Boutcher et al., 2013 32 (TG: 16; CG: 16)
Age: TG: 23.0 ± 4.0; CG: 21.1 ± 2.4
100% female
Polar S810i chest belt
Spontaneous
Supine
n.r.
RHR, LF (ln, ms2), HF (ln, ms2), LF nu, HF nu BF, BM, VO2 max 15 min HIIE (cycle ergometer)
12 weeks
3 sessions
yes
Brown et al., 2014 73 (NW: 27; BW: 27, CG: 19) (Baseline: N=94)
Baseline:
Age: NW: 46.3 ± 9.4; BW: 39.3 ± 10.3; CG: 40.2 ± 11.0
NW: 81% male; BW: 73% male; CG: 83% male
eMotion sensor ECG
n.r.
Sitting
n.r.
RHR, ln HF BM, BMI, BP, HRR 3 min Walking
8 weeks
2 sessions
Yes
Buchheit et al., 2010 14
Age: 36 ± 7
100% male
Polar S810 chest belt
Spontaneous
Supine
n.r.
RHR, ln RMSSD (weekly average of 1st and 8th week) BF, BM, HRR 5 min Endurance (continuous runs and intervals)
8 weeks
3–4 sessions
No
Cheema et al., 2013 37 (TG: 18; CG: 19)
Age: TG: 37 ± 12; CG: 39 ± 13
7 men, 30 women
ECG (Sphygmocor)
Spontaneous
Supine
n.r.
RHR, ln SDNN, ln RMSSD, pNN50, ln HF, ln LF, ln LF/HF, ln TP 10 min Yoga
10 weeks
3 sessions
yes
Chu et al., 2015 52 (TG: 26, CG: 26)
Age: TG: 27.58 ± 5.72; CG: 24.85 ± 5.17
100% female
ECG
n.r.
Supine
1.024 Hz
LF nu, HF nu, LF/HF 10 min Yoga
8 weeks
2 sessions
Yes
Cooke and Carter, 2005 22 (TG: 12; CG: 10)
Age: TG: 21 ± 0.3; CG: 22 ± 0.7
TG: 1 woman; CG: 3 women
3-lead ECG
15 breaths/min
Supine
500 Hz
mRR, SDNN, LF, HF, LF nu, HF nu BR, SBP 5 min Resistance (whole body)
8 weeks
3 sessions
Yes (recreationally active)
da Silva et al., 2019 30 (HRVG: 15; CG: 15)
Age: HRVG: 25.8 ± 3.1; CG: 27.7 ± 3.6
100% female
Polar RS800CX
Spontaneous
Standing
n.r.
RMSSD HRR 3 min Endurance (running)
8 weeks
3 sessions
Yes (predefined training program)
Duarte et al., 2015 40 (TG: 22; CG: 18)
Age: TG: TL: 19.2 ± 1.0; TH:19.5 ± 1.2. CG: CL: 19.1 ± 0.3; CH:18.9 ± 0.6
100% male
3-lead ECG
Spontaneous
Supine
1.000 Hz
RHR, RMSSD, HF nu, LF nu, LF/HF HRR 5 min Endurance (running)
12 weeks
3 sessions
Yes
Gamelin et al., 2007 10
Age: 21.7 ± 2.2
100% male
Polar S810
12 breaths/min
Supine
1.000 Hz
mRR, SDNN, RMSSD, NN50, pNN50, ln (LF+HF), ln LF, ln HF, LF nu, HF nu, LF/HF, SD1, SD2 VO2 max 5 min (last 256 s for analysis) Endurance (intervals and continuous runs on a treadmill)
12 weeks
2–4 sessions
No
Heffernan et al., 2007 14
Age: 25.0 ± 1.1
100% male
1-lead ECG
12 breaths/min
Supine
1.000 Hz
mRR, SDNN, ln TP, ln LF, LF nu, ln HF, HF nu, LF/HF, SampEn, LZEn BF, BM, HRR, VO2 peak At least 200 NN intervals Resistance (whole body)
6 weeks
3 sessions
No
Heffernan et al., 2009 39
Age: African Americans: 22 ± 1; Whites: 24 ± 1
100% male
1-lead ECG
12 breaths/min
Supine
1.000 Hz
mRR, RMSSD, pNN50, ln TP, ln LF, LF nu, ln HF, HF nu, ln LF/HF, SampEn BF, BM, BR, HRR, VO2 peak 15 min (220–260 s for analysis) Resistance (whole body)
6 weeks
3 sessions
No
Heydari et al., 2013 38 (TG: 20; CG: 18)
Age: 24.9 ± 4.3
100% male
Polar RS800CX
Spontaneous
Supine
1.000 Hz
RHR, RMSSD, pNN50, ln + ms2 (TP HF, LF, VLF) BM, BMI, BP, BR, VO2 max 30 min HIIE (8 s sprints on cycle ergometer)
12 weeks
3 sessions
Yes
Kim et al., 2017 34 (MAT: 12: HAT: 12; CG: 10)
Age: MAT: 24.08 ± 0.62; HAT: 23.25 ± 0.63; CG: 23.30 ± 0.47
100% male
Polar RS800CX
15 breaths/min
Sitting
256 Hz
RHR, RMSSD, pNN50, HF, HF nu, LF nu, LF/HF, SD1, SD1/SD2 BMI, BP, VO2 max 10 min Endurance (walking/running on a treadmill)
8 weeks
3 sessions
Yes
Kiviniemi et al., 2010 53 (ST: 14; HRV-I: 14: HRV-II: 10; CG: 15)
Age: Men: ST: 37 ± 3; HRV-I: 35 ± 4; CG: 34 ± 4. Women: ST: 34 ± 4; HRV-I: 33 ± 4; HRV-II: 35 ± 4; CG: 34 ± 4
21 men, 32 women
12-lead ECG
Spontaneous
2 min sitting and 3 min standing
n.r.
RHR, SD1 VO2 peak 5 min Endurance (running, walking or cycling)
8 weeks
at least 5 sessions
Yes
Martinmaki et al., 2008 11
Age: 36.8 ± 7.2
100% male
Polar Electro
Spontaneous
Supine, sitting and standing
1.000 Hz
RHR, TP, HF, LF VO2 peak 3 × 3 min Endurance (cycling, running, Nordic Walking)
14 weeks
2 sessions
No
McHugh et al., 2012 16
Age: 23.94 ± 5.57 (post)
7 males, 9 females
2-lead ECG
12 breaths/min
Supine
1.000 Hz
HF nu, LF/HF BF, BM, BMI, HRR, VO2 max 5 min Endurance (recreational jogging)
7 weeks
2 sessions
No
Moreira et al., 2017 18 (TG: 10; CG: 8)
Age: TG: 25.4 ± 3.3; CG: 29.6 ± 6.3
100% male
Polar RS800CX
n.r.
Sitting
n.r.
RHR, RMSSD, mRR, pNN50, SD1 BP 20 min Capoeira
10 weeks
1 session
Yes
Nuuttila et al., 2017 24 (HRVG, 13; PD: 11)
Age: HRVG: 29 ± 4: PD: 31 ± 5
100% male
Morning: Garmin 920XT; night: Firstbeat Bodyguard Decvice
n.r.
Supine
n.r.
RHR, RMSSD, LF, HF, TP BF, BM, VO2 max 3 min morning, 4 h night HIT [running and resistance (whole body)]
8 weeks
6 sessions
No
Pal et al., 2014 60 (20-29y, 30–39y, 40–49y; 20 in each group)
Age: AG I: 20–29; AG II: 30–39; AG III: 40–50
100% male
ECG (ProComp)
n.r.
Supine
n.r.
RHR, mRR, SDNN, RMSSD, pNN50, HF nu, LF nu, LF/HF, TP BM, BMI, BP 5 min Yoga
3 months
6 sessions
No
de Rezende Barbosa et al., 2016 29 (FTG: 13; CG: 16)
Age: FTG: 23.0 ± 2.1; CG: 20.6 ± 1.3
100% female
Polar S810i chest belt
Spontaneous
Supine
n.r.
mRR, RRtri, TINN, SD1, SD2, SD1/SD2 20 min Resistance (whole body)
12 weeks
3 sessions
Yes
Schumann et al., 2017 24 (ST: 14; TLG: 10)
Age: 34.0 ± 7.0
100% male
Polar RS800CX
n.r.
Supine and standing
n.r.
RHR, RMSSD, HF, LF, LF/HF (12th vs. 24th week) BF, BM, VO2 max (12th vs. 24th week) 180 s supine, 120 s standing Endurance (focused on running)
12 weeks
4–6 sessions
No
Sousa Fortes et al., 2018 31 (CLG: 10; MS: 11; CG: 10)
Age: CL: 22.04 ± 1.7; MS: 21.72 ± 1.7; CG: 21.85 ± 1.9
100% male
Polar RS800CX
n.r.
n.r.
1.000 Hz
Ln RMSSD 5 min Resistance (bench press and leg press)
8 weeks
3 sessions
Yes
Varela-Sanz et al., 2017 31 (TT: 11, PT: 10, CG: 10)
Age: TT: 22.36 ± 2.62; PT: 21 ± 2.71; CG: 22.2 ± 2.44
26 men, 5 women
Polar S800
n.r.
Supine and standing
n.r.
RHR, SDNN, RMSSD, LF, HF BM, BMI, VO2 max (estimated) n.r. 2x endurance (brisk walking or running) and resistance (bench press and half squat), 1x endurance
8 weeks
3 sessions
Yes
Wu et al., 2011 47 (TG: 22; CG: 25; Follow-up: 17)
Age: TG: 21.0 ± 1; CG: 21.0 ± 0.9
100% female
1-lead ECG
n.r.
Sitting
n.r.
RHR, SDNN, RMSSD, LF, HF, LF nu, HF nu BMI 5 min Endurance (running on a treadmill)
6 weeks
3 sessions
yes

AG, age group; BF, body fat; BM, body mass; BMI, body mass index; BP, blood pressure; BR, baroreflex sensitivity; BW, built walk group; CG, control group; CH, control group with high levels of HF at baseline; CL, control group with low levels of HF at baseline; CLG, clustering group; ECG, electrocardiography; FTG, functional training group; HAT, high-intensity aerobic training; HF (nu), power in high frequency range (in normalized units); HIIE, high-intensity intermittent exercise; HRR, heart rate recovery; HRV-I and II, HRV guided training based on daily HRV measurements; HRVG, HRV guided training group; IHG3, isometric handgrip training 3 days per week; IHG5, isometric handgrip training 5 days per week; LF (nu), power in low frequency range (in normalized units); ln, natural logarithm; LZEn, Lempel-Ziv entropy; MAT, moderate-intensity aerobic training; MS, multi-sets group; mRR, mean RR interval; NN50, number of pairs of adjacent NN intervals differing by more than 50 ms in the entire recording; n.r., not reported; NW, nature walk group; PD, predetermined training group; pNN50, NN50 count divided by the total number of all NN intervals; PT, polarized training group; RHR, resting heart rate; RMSSD, square root of the mean of the sum of the squares of differences between adjacent NN intervals; RRtri, HRV triangular index; SampEn, sample entropy; SBP, systolic blood pressure; SD1, standard deviation of instantaneous beat-to-beat variability, extracted from Poincaré Plot; SD2, standard deviation of the long-term variability, extracted from Poincaré Plot; SDNN, standard deviation of NN intervals; ST, standard training group; TG, training group; TH, training group with high levels of HF at baseline; TINN, baseline width of the minimum square difference triangular interpolation of the highest peak of the histogram of all NN intervals; TL, training group with low levels of HF at baseline; TLG, training load-guided (based on estimated cumulated training load); TP, total power; TT, traditional-based group; VLF, power in very low frequency range; VO2 max, maximum oxygen consumption; VO2 peak, peak oxygen consumption; α1, short-term component of Detrended Fluctuation Analysis.