High Intensity Interval Training Leads to Similar Inflammatory Activation as Seen With Traditional Training in Chronic Heart Failure
Question
To evaluate acute and temporal inflammatory responses after HIIT compared with traditional steady-state exercise training in physically inactive, low-fitness men living with chronic heart failure.
Summary
This randomized acute exercise trial compared one supervised cycle-ergometer HIIT session with one matched steady-state session in 14 physically inactive men with chronic heart failure. HIIT used repeated two-minute phases at 90% and 40% heart-rate or VO2 reserve, while steady-state exercise used continuous work at 65% reserve; both had five-minute warm-up, 20 minutes conditioning exercise, and five-minute cool-down. Inflammatory markers were measured before exercise, immediately after, and up to 48 hours later. IL-6 rose immediately after exercise and returned toward baseline, but HIIT did not produce greater inflammatory activation than steady-state exercise.
Methodology
- Fourteen physically inactive men with chronic heart failure, peak aerobic power below 25 mL/kg/min, and left ventricular ejection fraction below 35%, randomized to steady-state or HIIT cycling.
- 14 participants.
- Cycle ergometry.
- Work intervals: 2 minutes at 90% heart-rate or VO2 reserve.
- Recovery: 2 minutes active recovery at 40% heart-rate or VO2 reserve.
- Intensity: 90% reserve work phases and 40% reserve recovery phases; average HIIT RPE 4.3 and total work 60,943 J.
- 30 minutes including warm-up and cool-down; 20 minutes conditioning exercise.
- Single acute session.
- Single session with 48-hour biomarker follow-up.
- Randomized controlled acute exercise trial comparing a single HIIT bout with a single steady-state cycling bout.
- Interleukin-6, Interleukin-8, Interleukin-10, and TNF-alpha were tracked.
Outcomes
IL-6
IL-6 increased immediately after exercise as a main effect of time and returned near baseline at later timepoints, but there was no significant group difference or time-by-group interaction.
Time effect F(4,48)=3.484, p=0.014; group effect F(1,12)=1.803, p=0.204; time-by-group F(4,48)=0.874, p=0.486.
IL-8
IL-8 did not significantly change following exercise in either group.
Time effect F(4,48)=1.339, p=0.269; group effect F(1,12)=0.931, p=0.354; time-by-group F(4,48)=1.759, p=0.153.
IL-10
IL-10 showed no significant main effect of time, no group difference, and no time-by-group interaction.
Greenhouse-Geisser time effect F(1.7,19.8)=2.861, p=0.089; group effect F(1,12)=0.080, p=0.782; interaction F(1.7,19.8)=1.863, p=0.185.
TNF-alpha
TNF-alpha did not significantly differ over time, between groups, or by interaction.
Time effect F(4,48)=0.305, p=0.873; group effect F(1,12)=0.902, p=0.361; interaction F(4,48)=0.412, p=0.799.
C-reactive protein
CRP showed no significant main effect of time, group effect, or time-by-group interaction.
Greenhouse-Geisser time effect F(1.5,18.4)=0.855, p=0.414; group effect F(1,12)=1.980, p=0.185; interaction F(1.5,18.4)=0.442, p=0.598.
Exercise matching
Average session heart rate, work rate, METs, rate-pressure product, and total work did not significantly differ between the HIIT and steady-state groups.
The paper reports no significant differences between training groups for average exercise responses.
Insights
- In a supervised cardiac rehabilitation context, a matched-volume 2-minute on, 2-minute off cycling HIIT bout did not produce greater acute inflammatory activation than steady-state cycling in this small chronic heart failure sample.
- For clinical populations, HIIT interpretation depends on screening, monitoring, individualized intensity, and total workload matching.
- This paper informs inflammatory safety boundaries, not general long-term HIIT effectiveness.
Limitations
- Small sample size.
- Convenience sample.
- Potential selection bias because participants self-selected into exercise research.
- All participants were male.
- Unadjusted analyses did not control for age, medications, CHF class, or comorbid disease.
- Single acute exercise bout does not generalize to long-term training effects.
Safety
- Adverse-event counts were not reported.
- The acute exercise bout was supervised with 3-lead telemetry, portable heart-rate monitoring, RPE, and blood-pressure measurement.
- Exercise stress testing used explicit termination criteria including ischemic ECG changes, blood-pressure thresholds, dyspnea, and pain.
- The authors concluded there was no indication of excessive inflammatory activation after matched-volume HIIT.