The Study
Effects of Low Dose Caffeine on Post-Exercise Heart Rate Variability: A Double-Blind Placebo-Controlled Trial.
This study gave some people caffeine and some a fake pill after walking on a treadmill, then measured their heart rhythms. It found that with caffeine, their heart rate settled down a little faster — but only in young, healthy people. We can't say caffeine definitely causes this, because the group was tiny and other things like sleep or diet might have played a role.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
After walking at a moderate pace, people who chewed caffeine gum had better heart rate recovery signals than those who chewed placebo gum.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 560 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — higher HRV means your heart is recovering better and your body is shifting from 'fight-or-flight' to 'rest-and-digest' mode faster.
- 2Caffeine (170mg) increased HRV markers (SDNN, LF, HF, SD1) by 15–30% during 10–20 minutes after exercise, with medium effect sizes (d=0.59–0.70).
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
International journal of exercise science
Year
2022
Authors
Cagney T. Sargent, Tareq K Shahbal, A. E. Carrillo, T. Amorim, Jason R. Edsall, Emily J. Ryan, E. Ryan
Related Content
Claims (6)
High levels of caffeine maintain continuous activity in the body's fight-or-flight system and reduce activity in the rest-and-digest system.
In healthy young adults, consuming 170mg of caffeine after moderate exercise does not reduce parasympathetic nervous system activity during the 10–30 minutes following exercise, as measured by high-frequency power and SD1.
Taking 170mg of caffeine after exercise does not change heart rate or the time between heartbeats during recovery, and this means any effect caffeine has on heart rate variability is not due to changes in average heart rate.
After moderate exercise, healthy young adults who chew a caffeine gum containing 170mg show higher heart rate variability during the first 30 minutes of recovery compared to those who do not.
A 170mg dose of caffeine taken after moderate exercise increases the variability of heart rate and low-frequency heart rate oscillations during the first 20 minutes of recovery, indicating a measurable change in autonomic nervous system activity.
Taking 170 mg of caffeine after moderate exercise causes measurable changes in heart rate variability, with the largest effects on SDNN, LF, and HF occurring between 10 and 20 minutes after exercise.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.