# High Intensity Interval Training Leads to Similar Inflammatory Activation as Seen With Traditional Training in Chronic Heart Failure PMID: 35211515 Journal: Frontiers in cardiovascular medicine Published: 2022-02-08 Authors: Taylor AG, Ignaszewski AI, Bredin SSD, Hill JS, Shellington EM, Warburton DER ## 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. ## Population - 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. - Sample size: 14 - Age: Steady-state group mean 60.1 years, SD 6.7; HIIT group mean 57.9 years, SD 9.8. - Sex: All male. - Fitness level: Low fitness; VO2peak 14.9 +/- 5.3 mL/kg/min in steady-state group and 12.5 +/- 3.9 mL/kg/min in HIIT group. - Health status: Chronic heart failure with ejection fraction below 35%; NYHA class I-IIIa; multiple cardiac medications common. ## Methodology - Randomized controlled acute exercise trial comparing a single HIIT bout with a single steady-state cycling bout. - Single acute exercise session with inflammatory-marker follow-up through 48 hours post-exercise. - Clinical exercise research setting at St. Paul's Hospital and University of British Columbia, using supervised cycle ergometry. - Randomized and controlled study design. ## Protocol - High intensity interval training cycle exercise. - Modality: 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. - Sets or repetitions: Five high-intensity phases and five recovery phases across 20 minutes. - Intensity: 90% reserve work phases and 40% reserve recovery phases; average HIIT RPE 4.3 and total work 60,943 J. - Session duration: 30 minutes including warm-up and cool-down; 20 minutes conditioning exercise. - Frequency: Single acute session. - Program length: Single session with 48-hour biomarker follow-up. - Progression: None; work rates individualized from cardiopulmonary exercise testing. - Steady-state cycle exercise. - Modality: Cycle ergometry. - Work intervals: Continuous 20-minute conditioning exercise. - Sets or repetitions: One continuous bout. - Intensity: 65% heart-rate reserve or VO2 reserve; average RPE 4.2 and total work 65,486 J. - Session duration: 30 minutes including warm-up and cool-down; 20 minutes conditioning exercise. - Frequency: Single acute session. - Program length: Single session with 48-hour biomarker follow-up. - Progression: None; work rate individualized from cardiopulmonary exercise testing. ## Outcomes ### IL-6 Status: mixed 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 Status: no clear change 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 Status: no clear change 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 Status: no clear change 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 Status: no clear change 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 Status: no clear change 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. ## Practical 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 And Adherence - 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. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/35211515/) (pubmed) - [DOI](https://doi.org/10.3389/fcvm.2021.752531) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8860824/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.