Table 2.
HIIT studies in non-clinical populations
| Article | HIIT/SIT protocol | Outcomes | Feasibility/tolerability |
|---|---|---|---|
| Aboarrage et al. (2018) [18] |
Frequency: 3×/week for 24 weeks Intervals: 20 bouts at “all-out” intensity for 30-s Rest: 30-s passive recovery Time: 20 min Modality: Jump-based aquatic training |
There was a significant increase in bone mineral density of the lumbar spine, total femur, and whole body of HIIT compared to the control group. Functional ability was also improved in HIIT compared to control as measured by the timed up-and-go test (improved by − 11 ± 4%) and Chair Stand (improved by 17 ± 3%). |
Dropouts: None reported AEs: None reported |
| Adamson et al. (2019) [19] |
Frequency: 2×/week for 10 weeks Intervals: 6–10 intervals of “all-out” or submaximal intensity for 6s Rest: 1-min passive recovery Time: 12 min max Modality: Cycle ergometer |
Compared to control there was a significant decrease in SIT group in systolic (7%), diastolic (9%), pulse pressure (9%), and MAP (8%) as well as improvement in physical function (timed up and go, loaded 50m walk, and stair climb power). Additionally, ratios of total cholesterol/HDL cholesterol and LDL cholesterol/HDL cholesterol were significantly reduced compared to control after SIT. |
Dropouts: None Compliance: 100% completion rate by all participants. AEs: None reported |
| Bailey et al. (2017) [20] |
Frequency: Single session Intervals: 12 intervals at 70% PPO for 1 min Rest: 1 min at 10% PPO Modality: Cycle ergometer |
After MCT there was an immediate increase in FMD that normalized after 1h in both fitness groups. After HIIT, FMD decreased immediately and 1 h post-intervention in the lower fit group but increased after 1h in the higher-fit group. | Not provided |
| Brown et al. (2021) [21] |
Frequency: 2×/week for 6 months Intervals: 11 intervals at 18 RPE on Borg scale for 1 min Rest: 2-min active recovery Modality: Cycle ergometer |
The HIIT group experienced greater increases in fitness than the moderate-intensity and control groups. However, there was no direct effect of exercise on cognition. |
Compliance: No difference in exercise attendance between HIIT (85.5 ± 12.4%) and MCT (86.3 ± 9.8%) AEs: No serious AEs recorded Dropouts: 7 withdrew during the intervention period (HIIT: 1 due to medical illness and 1 due to pain after exercise; MCT: 2 due to medical illness and 1 due to refusing participation; control: 1 due to medical illness and one refused participation) |
| Bruseghini et al. (2015) [22] |
Frequency: 3×/week for 8 weeks Intervals: 7 intervals at 85–95% VO2max for 2 min Rest: Active recovery at 40% VO2max for 2 min Modality: Cycle ergometer |
Cardiovascular fitness significantly improved and systolic BP decreased in the HIIT group. Both HIIT and RT resulted in quadriceps hypertrophy but there was only an associated increase in strength after RT. | Not provided |
| Bruseghini et al. (2020) [23] |
Frequency: 3×/week for 8 weeks Intervals: 7 intervals at 85–95% VO2max for 2 min Rest: 2 min at 40% VO2max Modality: Cycle ergometer |
During HIIT, significant changes were observed in moderate and vigorous physical activity, average daily metabolic equivalents (METs), physical activity level, and activity energy expenditure (p < 0.05) but not in total energy expenditure. Sleep and sedentary time, and levels of light physical activity remained constant. | Not given |
| Coswig et al. (2020) [24] |
Frequency: 2×/week for 8 weeks Intervals: 4 intervals at 85–95% HRmax for 4 min Rest: 4 min at 65% HRmax Modality: Treadmill |
HIIT promoted greater reductions in body mass (HIIT = − 1.6 ± 0.1 kg; MICT = − 0.9 ± 0.1 kg; MIIT = − 0.9 ± 0.1 kg; p = 0.001), fat mass (HIIT = − 2.2 ± 0.1%; MICT = − 0.7 ± 0.1%; MIIT = − 1.2 ± 0.1%; p<0.001), resting heart rate (HIIT = − 7.3 ± 0.3%; MICT = − 3.6 ± 0.3%; MIIT = − 5.1 ± 0.3%; p < 0.001) and greater improvement in the chair stand test. | Dropouts: None |
| Donath et al. (2015) [25] |
Frequency: Single session Intervals: 4 intervals at 90–95% HRmax for 4 min Rest: 3 min at 70% HRmax Modality: Treadmill |
Standing balance performance: seniors demonstrated inverted ankle muscle coordination pattern compared to young adults which was unchanged by HIIT. Ankle co-activation was twofold elevated in seniors compared to young adults during single limb stance with eyes open and was also not affected by HIIT. | Not given |
| Herrod et al. (2020a) [26] |
Frequency: 3×/week for 2, 4, or 6 weeks Intervals: 5 intervals at 90–110% of PPO for 1 min Rest: 90 s of active recovery Modality: Cycle ergometer |
Anaerobic threshold was increased only after 4 (+1.9 ± 1.1 mL/kg/min) and 6 weeks (+1.9 ± 1.8 mL/kg/min) of HIIT (both p < 0.001), with 6-week HIIT required to elicit improvements in VO2peak (+3.0 ± 6 mL/kg/min; p = 0.04). Exercise tolerance increased after 2 (+15 ± 15 W), 4 (+17 ±11 W), and 6 weeks (+16 ± 11 W) of HIIT (all p < 0.001), with no difference in increase between the groups. |
Compliance: 100% training compliance reported AEs: None reported |
| Herrod et al. (2020b) [27] |
Frequency: 3×/week for 6 weeks Intervals: 5 intervals at 90–110% of PPO for 1 min Rest: 90 s of active recovery Modality: Cycle ergometer |
For SBP, there was a main effect of time (P<0.001) and a significant group x time interaction (P= 0.04), with significant reductions in both the HIIT (142(15) vs. 133(11); −9(9) mmHg, P<0.001) and IHG (139(15) vs. 130(12); −9(9)mmHg, P= 0.002) groups. ☐ere was no significant change in either the RIPC (138(15) vs. 134(14); −4(5), P= 0.17) or control (130(10) vs. 128(10); −1(6), P= 0.96) groups Systolic blood pressure significantly decreased in the HIIT (− 9 ± 9 mmHg) and isometric handgrip training groups (− 9 ± 9 mmHg). There was no significant change in the control or remote ischemic preconditioning groups. |
Mean (SD) training compliance was 99(3)%, and there were no adverse events Mean (SD) training compliance was 99(3)%, and there were no adverse events Compliance: Mean (SD) was 99(3) % AEs: None reported |
| Hwang et al. (2016) [28] |
Frequency: 4×/week for 8 weeks Intervals: 4 intervals at 90% HRpeak for 4 min Rest: 3 min at 70% HRpeak Modality: Non-weight-bearing all-extremity ergometer |
Primary outcome—see feasibility and tolerability. Secondary outcomes—VO2peak improved by 11% and ejection fraction improved by 4% in HIIT, no change was seen in MCT or control. Insulin resistance decreased by 26% in the HIIT group only. Diastolic function, body composition, lipid, and glucose did not change. |
Dropouts: Of 51 participants randomized, 16% did not complete the study (control: 2 unable to contact; MCT: 2 lack of motivation, 1 family conflict, 1 schedule conflict; HIIT: 1 family conflict, 1 schedule conflict) Compliance: rate by participants was 88% AEs: None in HIIT HIIT was deemed to be feasible |
| Kim et al. (2017) [29] |
Frequency: 4×/week for 8 weeks Intervals: 4 intervals at 90% HRpeak for 4 min Rest: 3 min active recovery at 70% HRpeak Modality: All-extremity non-weight-bearing ergometer |
Arterial stiffness improved after MCT only (decrease in carotid to femoral pulse wave velocity and increase in common carotid artery compliance). No change was seen in HIIT. |
Dropouts: 9 of 49 subjects did not complete intervention (HIIT: family issues, schedule conflict; MCT: lack of motivation, inability to contact for follow-up. 2 subjects were excluded from analysis (1 in MCT due to unrelated illness, 1 in control group due to non-compliance). Compliance: Similar between MCT and HIIT (both 90%). AEs: None reported Exercise training was described as "well-tolerated.” |
| Kovacevic et al. (2020) [30] |
Frequency: 3×/week for 12 weeks Intervals: 4 intervals at 90–95% HRpeak for 4 min Rest: 3 min active recovery at 50–70% HRpeak Modality: Treadmill |
HIIT and MCT interventions induced similar cardiorespiratory fitness adaptations from pre- to post-test, such that exercise training led to the greatest increases in predicted VO2peak. High-interference memory significantly improved following HIIT but not MCT or control. There was no main effect of group on brain-derived neurotrophic factor |
Dropouts: 13 participants withdrew during training (HIIT = 3, MCT = 5, stretching = 5) Compliance: All participants completed at least half of training protocol. |
| Krusnauskas et al. (2018) [31] |
3 SIT protocols: 1) 6 intervals of 5 s at “all-out” intensity (90-s rest), 2) 3 intervals of 30 s at “all-out” intensity (4-min rest), or 3) 3 intervals of 60 s at submaximal intensity (4-min rest) Frequency: Single session Modality: Cycle ergometer |
Decrease in torque ratio represented low-frequency fatigue and was more evident in the 30 s and 60 s protocols. In young women, low volume (6 × 5 s) exercise induces physiological stress and is effective. In older women, longer intervals (3 × 60 s) are more stressful than shorter but still tolerable. | Acceptance of protocol: 6 × 5 s cycling was the most preferred method in both age groups. Perceived enjoyment was similar in both groups. |
| Linares et al. (2020) [32] |
Frequency: Single session Intervals: 10 intervals at 90% PPO for 1 min Rest: 1 min at 10% PPO Modality: Cycle ergometer |
There were similar peaks in oxygen consumption (in women alone) and in HR (both women and men) when comparing HIIT and maximal exercise. There was a greater cardiopulmonary response to HIIT compared with MCT. When PPO was used for exercise prescription there was considerable individual variability in work intensity seen. | Not given |
| McSween et al. (2020) [33] |
Frequency: Single session Intervals: 4 intervals at 85–95% HRpeak for 4 min Rest: 3 min at 50-65% HRpeak Modality: Cycle ergometer |
In lower baseline learning performers, the MCT group performed significantly better at the immediate recall task when compared with the stretching group, whereas this difference was not observed between the stretching and HIIT group and the MCT and HIIT group. | Not given |
| Mejias-Pena et al. (2016) [34] |
Frequency: 2×/week for 8 weeks Intervals: 0–4 intervals (progressive) at 90–95% HRmax for 1 min Rest: 70-75% HRmax for 4–7 min Modality: Cycle ergometer |
Less loss of autophagic activity was seen in older adults after HIIT. Peak oxygen uptake increased post-intervention in the training group. | Not given |
| Mekari et al. (2020) [35] |
Frequency: 3×/week for 6 weeks Intervals: 15-s intervals at 100% PPO Rest: 15-s passive recovery at 0% PPO Modality: Cycle ergometer |
VO2max significantly improved in all groups following training, but HIIT and MCT improved more than RT. The HIIT group had the greatest improvement in VO2max. Regarding cognitive flexibility, the HIIT group exhibited a faster reaction time (from 1250 ± 50 to 1100 ± 50 ms; p < 0.001) in switching. | Not given |
| Nakajima et al. (2010) [36] |
Frequency: 2×/week for 6 months Intervals: 3 min at > 70% peak aerobic capacity Rest: 3 min at 40% peak aerobic capacity Time: > 26 min Modality: Walking |
Methylation of ASC gene (inflammatory mediator involved in initiating innate immunity) decreased significantly with age (young control vs. older control, p<0.01), which is indicative of an age-dependent increase in ASC expression. Compared to the older control group, the degree of ASC methylation was higher in the older HIIT group. | Not given |
| Nederveen et al. (2015) [37] |
Frequency: Single session Intervals: 10 intervals at 90-95% VO2max for 1 min Rest: “low-intensity” for 1 min Modality: Cycle ergometer |
Satellite cell response to exercise: Specific to type 1 fibers, expansion occurred 24 and 48 h post-treatment in the HIIT group. HIIT and RT groups showed greater response 24-h post-treatment than MCT. HIIT was nearly as effective as RT in increasing the number of active satellite cells following an acute bout of exercise. | Not given |
| O’Brien et al. (2020) [38] |
Frequency: 3×/week for 6 weeks Intervals: 15-s intervals at 100% PPO Rest: 15-s passive recovery at 0% PPO Modality: Cycle ergometer |
Resting HR decreased in the MCT group only. HIIT group had lower systolic, diastolic, and mean arterial blood pressures post-training but MCT only decreased diastolic blood pressure. RT did not change any systemic resting hemodynamic measurements. Resting brachial artery blood flow and vascular conductance (both, p < 0.003) were greater after HIIT only. The HIIT and MCT similarly increased brachial artery flow-mediated dilation (pre–post both, p < 0.001), but only HIIT improved brachial artery low flow-mediated constriction. | Not given |
| Osuka et al. (2017) [39] |
Frequency: Single session Intervals: 3 intervals at 75–85% VO2peak for 2–3 min Rest: 1-2 min at 50% VO2peak Modality: Cycle ergometer |
Primary—feasibility. Secondary—exercise intensity achieved: %VO2peak achieved during the interventions was greater in HIIT than MCT, %HRpeak achieved during exercises were different between protocols throughout, including their peak HR reached. The ratings of perceived exertion were similar between groups. |
Compliance: Completion rates were similar between treatments (MCT: 95.2%, HIIT: 100%) AEs: No severe AEs reported. During HIIT cool-down, one participant had transient asymptomatic tachycardia for less than 1 min. |
| Stockwell et al. (2012) [40] |
Frequency: Single session Intervals: 10 intervals at 70% VO2max for 1 min Rest: 30% VO2max for 1 min Modality: Cycle ergometer |
Greater HR changes were seen in HIIT compared to MCT. Compared to MCT, VO2 was 16% higher during HIIT though this was not statistically significant. Similar ratings of perceived exertion were seen for both protocols. |
Dropouts: None Acceptance of protocol: Self-report suggested that enjoyability of HIIT was higher than MCT and may contribute to increased adherence. |
| Storen et al. (2017) [41] |
Frequency: 3×/week for 8 weeks Intervals: 4 intervals at 90–95% HRmax for 4 min Rest: 3 min at 70% HRmax Modality: Treadmill and cycling |
After HIIT, all age cohorts significantly increased VO2max by 9–13%. These changes did not differ between age cohorts. No change was seen in HRmax. |
Compliance: Participants were only included in results if compliance was > 80% and if their initial VO2max was representative of their age group. Mean compliance was reported as 92% +- 4% (no significant difference between age groups or gender) AEs: None reported |
| Venckunas et al. (2019) [42] |
3 SIT protocols: 1) 6 intervals of 5 s at “all-out” intensity (90-s rest), 2) 3 intervals of 30 s at “all-out” intensity (4-min rest), or 3) 3 intervals of 60 s at submaximal intensity (4-min rest) Frequency: Single session Modality: Cycle ergometer |
All protocols increased the blood lactate concentration and decreased maximal voluntary contraction and electrically stimulated knee extension in young and especially untrained young men. The higher-volume sessions more markedly suppressed contractile function and also increased serum testosterone in untrained groups. | Not given |
| Vogel et al. (2011) [43] |
Frequency: 2×/week for 9 weeks Intervals: 6 intervals at 90% Max tolerated power for 1 min Rest: VT1 for 4 min Modality: Cycle ergometer |
Significant improvement of maximum tolerated power, VO2peak and maximal minute ventilation was seen for both age groups compared to baseline. In the “older senior” group post-HIIT, some measures of cardio-respiratory response were not statistically different from the “young senior” responses pre-HIIT (in women: maximum tolerated power; in men and women: VO2peak, maximal minute ventilation, first ventilatory threshold). |
Compliance: 100% adherence rate to training program AEs: No training-related AEs reported |
| Windsor et al. (2018) [44] |
Frequency: Single session Intervals: 12 intervals at 70% PPO for 1 min Rest: 1 min at 10% PPO Modality: Cycle ergometer |
Plasma cytokine concentrations: IL6 & 10 increased in both groups immediately post either HIIT or MCT; no difference between exercise and non-exercisers; no changes in TNF-a. | Not given |
| Wyckelsma et al. (2017) [45] |
Frequency: 3×/week for 12 weeks Intervals: 4 intervals at 90–95% HRpeak for 4 min Rest: 4 min at 50–60% HRpeak Modality: Cycle ergometer |
HIIT increased VO2peak by 16% and increased the peak work rate by 11% with no significant reduction in the rise of [K+]. Muscle Na+,K+-ATPase NKA content increased by 11% in the HIIT group with no change in control group. |
Dropouts: 1 due to ill health unrelated to study, one due to high blood pressure after exercise. Compliance: Not including dropouts, all completed at least 83% of sessions AEs: 5 participants had mild vasovagal episodes during training without further incidents |
| Yasar et al. (2019) [41] |
Frequency: 2 sessions separated by 3 or 5 days of recovery Intervals: 3 intervals of 20 s “all-out” intensity Rest: 3 min self-paced Modality: Cycle ergometer |
A large effect of age was seen on PPO, with the older group having a lower PPO. Both groups could recover in 3 or 5 days. | Not given |
| Yoo et al. (2017) [46] |
Frequency: Single session Intervals: 4 intervals at 90% HRpeak for 4 min Rest: 3 min at 70% HRpeak Modality: Treadmill |
In men, FMD was similarly attenuated by 45% after HIIT and by 37% after MCT. In women, FMD did not significantly change after HIIT or MCT. | Not given |
HIIT high-intensity interval training; SIT sprint interval training; MCT moderate-intensity continuous training; RT resistance training; MAP mean arterial pressure; HDL high-density lipoprotein; LDL low-density lipoprotein; FMD flow-mediated dilation; PPO peak power output; HR heart rate; VO2volume of oxygen consumption; AE adverse events