Acute-Phase Inflammatory Response to Single-Bout HIIT and Endurance Training: A Comparative Study
Question
Do acute inflammatory and metabolic blood-marker responses differ after a single low-volume HIIT cycling session compared with a traditional endurance cycling session in healthy untrained adults?
Summary
In seven healthy untrained young adults who completed both exercise sessions, a single sprint-style HIIT cycling session produced broadly similar short-term inflammatory blood-marker responses to a 45-minute endurance cycling session. The endurance session lowered the IL-6/IL-10 ratio at 30 minutes and MCP-1 two days later, while individual cytokines and CRP did not significantly change after either session.
Methodology
- Healthy untrained young adults without chronic disease, medication or supplement use, smoking, or regular structured training
- 7 participants.
- cycle.
- Work intervals: 30 seconds.
- Recovery: 240 seconds.
- Intensity: All-out supramaximal work bouts.
- About 25 minutes.
- Single session.
- Two single-session exercise visits separated by at least 7 days, with blood sampling before, 30 minutes after, and 2 days after each session.
- Randomized-order repeated-measures acute exercise study
- Inflammatory markers, and Metabolic markers were tracked.
Outcomes
CRP
CRP did not significantly change after either HIIT or endurance cycling.
Favours: no_difference
Cytokines
IL-1beta, IL-6, IL-10, and IGF-1 did not significantly change from baseline after either protocol.
Favours: no_difference
IL-6/IL-10
Endurance cycling reduced the IL-6/IL-10 ratio 30 minutes post-exercise.
Effect: -20%; P value/detail: 0.047; Favours: comparator
MCP-1
Endurance cycling reduced MCP-1 two days after exercise.
Effect: -17.9%; P value/detail: 0.03; Favours: comparator
Insights
- A very low-volume cycling HIIT session can be implemented with six 30-second all-out bouts and long recoveries, but this protocol may not be tolerable for every untrained participant.
- Acute biomarker equivalence should not be presented as evidence that HIIT improves long-term inflammation.
Limitations
- Very small analytic sample.
- Acute single-session design.
- Healthy young adults only.
- Biomarker outcomes rather than fitness, adherence, or clinical outcomes.
- One participant could not complete the HIIT protocol.
Safety
- No adverse events were reported in the article.
- One recruited participant was excluded because they could not complete the HIIT session.