Table 1.

Characteristics of 18 included studies examining the effect of high-intensity interval training on cardiorespiratory fitness.

Study	Year	Sample Population	Duration (week)	Group (n)	Modality/ Intensity	Repeated Bouts/ Frequency	Work/rest W/R Ratio	Exercise Time per Week (min)	CRF Outcomes
McManus et al. [18] Country: China Study design: RCT	2004	school children; n = 25 (25 boys; 10.3 ± 0.5 years)	8	HIIT (10) MICT (15)	Cycling (all-out) Cycling (85% HRmax)	Bouts: 7 (3 times weekly)	30 s/ 165 s 0.18	10.5 60	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Corte et al. [19] Country: Brazil Study design: RCT	2012	school children; n = 30 (9 boys; 10.4 ± 0.9 years)	12	HIIT (15) MICT (15)	Running (100% ${\dot{\mathrm{V}}\mathrm{O}}_{2\mathrm{peak}}$) Running (80% HRpeak)	Bouts: 3–6 (2 times weekly)	60 s/ 180 s 0.33	6–18 60–120	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Koubaa et al. [13] Country: Tunisia Study design: RCT	2013	obese children; n = 29 (29 boys; 13.0 ± 0.8 years)	12	HIIT (14) MICT (15)	Running (80–90% ${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$) Running (60–70% ${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$)	Bouts: NR (3 times weekly)	120 s/ 60 s 2.00	NA NA	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Farah et al. [16] Country: Brazil Study design: RCT	2013	obese children; n = 19 (9 boys; 15.1 ± 1.2 years)	24	HIIT (9) MICT (10)	Running (100% VT) Running (80% VT)	Bouts: NR (3 times weekly)	NA	NA NA	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Boer et al. [12] Country: Blegium Study design: RCT	2013	obese children; n = 32 (9 boys; 17.0 ± 3.0 years)	15	HIIT (17) MICT (15)	Running (110% VT) Running (100% VT)	Bouts: 10 (2 times weekly)	15 s/ 45 s 0.33	5 60	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Starkoff et al. [20] Country: USA Study design: RCT	2014	obese children; n = 27 (10 boys; 14.7 ± 1.5 years)	6	HIIT (14) MICT (13)	Cycling (90–95% APMHR) Cycling (65–70% APMHR)	Bouts: 10 (3 times weekly)	120 s/ 60 s 2.00	60 90	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Lee et al. [22] Country: Korea Study design: RCT	2015	school children; n = 20 (NR; 15.3 ± 2.2 years)	12	HIIT (10) MICT (10)	Running (≥80% HRR) Running (<40% HRR)	Bouts: NR (3 times weekly)	30 s/ 30 s 1.00	NA NA	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Murphy et al. [21] Country: USA Study design: RCT	2015	obese children; n = 13 (3 boys; 13.7 ± 2.0 years)	4	HIIT (6) MICT (7)	Cycling (80–90% HRmax) Cycling (65% HRmax)	Bouts: 10 (3 times weekly)	60 s/ 120 s 0.50	30 90	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Lazzer et al. [23] Country: Italy Study design: RCT	2016	obese children; n = 30 (30 boys; 13.7 ± 2.0 years)	3	HIIT (10) MICT (20)	Running (100% ${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$) Running (70% ${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$)	Bouts: 6 (3 times weekly)	40 s/ 300 s 0.13	12 120	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Kargarfard et al.-NW [15] Country: Iran Study design: RCT	2016	school children; n = 20 (NR; 12.2 ± 1.5 years)	8	HIIT (10) MICT (10)	Running (60–90% HRR) Running (60–70% HRR)	Bouts: 8-10 (3 times weekly)	240 s/ 120 s 2.00	96–120 150–180	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Kargarfard et al.-OB [15] Country: Iran Study design: RCT	2016	obese children; n = 20 (NR; 12.3 ± 1.3 years)	8	HIIT (10) MICT (10)	Running (60–90% HRR) Running (60–70% HRR)	Bouts: 8–10 (3 times weekly)	240 s/ 120 s 2.00	96–120 150–180	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Martinez et al. [24] Country: Spain Study design: RCT	2016	school children; n = 94 (52 boys; 8.2 ± 0.7 years)	12	HIIT (38) MICT (56)	Running and jumping (NR) Aerobic exercise (NR)	Bouts: NR (2 times weekly)	10–20 s / NR NA	40 40	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Messler et al. [25] Country: Germany Study design: RCT	2016	ADHD adolescents n = 28 (28 boys; 11.0 ± 1.0 years)	3	HIIT (14) MICT (14)	NR (95% HRpeak) Mixture (<70% HRpeak)	Bouts: 4 (3 times weekly)	240 s/ 180 s 1.33	48 180	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (L·min−1)
Dias et al. [11] Country: Australia Study design: RCT	2017	obese children; n = 47 (31 boys; 12.2 ± 2.1 years)	12	HIIT (25) MICT (22)	Cycling (85–95% HRmax) Cycling (60–70% HRmax)	Bouts: 4 (3 times weekly)	240 s/ 180 s 1.33	48 132	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Ingul et al. [26] Country: Norway Study design: RCT	2018	obese children; n = 41 (21 boys; 12.0 ± 2.3 years)	12	HIIT (17) MICT (24)	Cycling (85–95% HRmax) Cycling (60–70% HRmax)	Bouts: 4 (3 times weekly)	240 s/ 180 s 1.33	48 132	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)
Cvetkovic et al. [27] Country: Serbia Study design: RCT	2018	obese children; n = 21 (21 boys; 11–13 years)	12	HIIT (11) MICT (10)	Running (100% MAS) Running (NR)	Bouts: 5–10 (3 times weekly)	10–20 s / 10–20 s 1.00	7.5–15 180	Yo−Yo test distance
Morrissey et al. [28] Country: France Study design: non-RCT	2018	obese children; n = 29 (8 boys; 15.2±1.4 years)	12	HIIT (16) MICT (13)	Running (90–95 % HRmax) Running (60–70 % HRmax)	Bouts: 4–6 (3 times weekly)	120–150 s/ 90 s 1.33–1.66	24–45 120–180	20mSRT bouts
Biljon et al. [14] Country: South Africa Study design: RCT	2018	school children; n = 58 (26 boys; 11.1 ± 0.8 years)	5	HIIT (29) MICT (29)	Running (>80% HRmax) Running (65–70% HRmax)	Bouts: 10 (3 times weekly)	60 s/ 75 s 0.80	30 99	${\dot{\mathrm{V}}\mathrm{O}}_{2\max }$ (mL·kg−1·min−1)

APMHR, age predict maximal heart rate; CRF, cardiorespiratory fitness; HIIT, high-intensity interval training; HR_peak, peak heart rate; HR_max, maximal heart rate; HRR, heart rate reserve; MAS, maximal aerobic speed; MICT, moderate-intensity continuous training; NA, not applicable; NC, no changes P > 0.05; NR, not report; P_peak, peak power; V_peak, peak velocity; VO_2max, maximal oxygen uptake; VT, ventilatory threshold.