Vascular-endothelial adaptations following low and high volumes of high-intensity interval training in patients after myocardial infarction
Question
Is low-volume HIIT with less than 10 minutes at high intensity per session sufficient to improve endothelial function, oxidative stress, and carotid intima-media thickness in patients after acute myocardial infarction, and how does it compare with higher-volume HIIT and unsupervised physical activity recommendations?
Summary
This randomized clinical trial compared low-volume HIIT, high-volume HIIT, and unsupervised physical activity recommendations in 80 patients after acute myocardial infarction. Both supervised HIIT programs improved brachial artery flow-mediated dilation, lowered oxidized LDL, and slightly reduced carotid intima-media thickness compared with the control group. Low-volume HIIT used only 8 minutes per session in the high-intensity range and still produced favorable vascular-endothelial changes.
Methodology
- 80 clinically stable adults 1-6 months after acute myocardial infarction with preserved systolic function, randomized to attention control, low-volume HIIT, or high-volume HIIT.
- 80 participants.
- Treadmill one day and cycle ergometer one day each week.
- Work intervals: Treadmill 4 minutes at R3; cycle 30 seconds at R3.
- Recovery: Treadmill 3 minutes at R2; cycle 60 seconds at R2.
- Intensity: R3 from VT2 to maximum HR, alternating with R2 between VT1 and VT2; controlled by HR and Borg RPE.
- LV-HIIT 20 minutes; HV-HIIT 20-40 minutes.
- 2 sessions/week on non-consecutive days.
- 16 weeks.
- Randomized clinical trial with three parallel groups and pre-post measurements.
- Flow-mediated dilation, Carotid intima-media thickness, Oxidized LDL, and Blood pressure were tracked.
Outcomes
FMD
FMD increased in both exercise groups compared with control: LV-HIIT had a 1.6-fold increase and HV-HIIT had a 1.9-fold increase.
LV-HIIT +58.8 +/- 8.5%; HV-HIIT +94.1 +/- 9.7%; ANOVA p < 0.001.
Endothelial dysfunction prevalence
Endothelial dysfunction prevalence decreased in both HIIT groups, from 92.9% to 60.7% in LV-HIIT and from 85.7% to 57.1% in HV-HIIT.
ANOVA p = 0.0018 for reduction in endothelial dysfunction.
Oxidized LDL
ox-LDL decreased in both HIIT groups compared with no variation in control, with a larger reduction in HV-HIIT.
LV-HIIT -5.2 +/- 2.2%; HV-HIIT -8.9 +/- 3.7%; ANOVA p < 0.001. Correlation between delta FMD and delta ox-LDL: LV-HIIT r = -0.376, p = 0.047; HV-HIIT r = -0.490, p = 0.008.
cIMT
cIMT decreased slightly in both HIIT groups compared with control, without meaningful difference between low and high volume.
LV-HIIT -3.0 +/- 1.1%, p = 0.0389; HV-HIIT -3.2 +/- 1.2%, p = 0.0305; ANOVA p = 0.019; low vs high p = 0.467.
Safety
No relevant adverse events were reported, and no participant dropped out.
Insights
- In supervised cardiac rehabilitation after AMI, less than 10 minutes of accumulated high-intensity work per session may be sufficient for favorable vascular-endothelial adaptations.
- Clinical HIIT protocols should report both total session duration and accumulated high-intensity time.
- Cardiac-risk HIIT translation requires screening, clinical supervision, individualized thresholds, and adverse-event monitoring.
Limitations
- Small sample size.
- Uneven gender distribution with 82.5% men.
- Sixteen-week duration may be short for atherosclerotic progression outcomes.
- Atherosclerosis was only evaluated in carotid arteries.
- Only one oxidative stress biomarker, ox-LDL, was used.
- Supplemental protocol details existed but were not used for this extraction.
Safety
- No relevant adverse events were reported throughout the intervention and supervised training sessions.
- All participants completed the 16-week training protocol.
- Patients were screened for clinical stability, preserved systolic function, and absence of high-risk exercise contraindications.