How Illness Affects HRV
Even minor illness significantly impacts HRV:
During illness: - Immune response activates sympathetic nervous system - HRV drops substantially (often 30-50%+) - Elevated resting heart rate - Poor sleep quality compounds the effect
Why this matters for training: - Suppressed HRV = impaired recovery capacity - Training while sick delays healing - Can progress to more serious illness - Risk of heart complications with some infections
Your HRV device often detects illness before you feel symptomatic.
Using HRV as an Early Warning
The pattern: - HRV drops 1-2 days before symptoms appear - You might feel "off" but not sick yet - This is your early warning
What to do when HRV drops unexpectedly: - Consider whether you're coming down with something - Reduce training intensity as a precaution - Extra sleep and nutrition - If illness develops, you've gotten a head start on recovery
False positives: - Not every HRV drop means illness - Could be hard training, alcohol, poor sleep - But unexplained drops warrant caution
Return to Training Protocol
The critical question: When is it safe to train again?
Don't rush based on: - "Feeling better" (often misleading) - Absence of fever (not sufficient) - Days since symptoms started
Use HRV instead: 1. Wait until symptoms fully resolve 2. Monitor HRV for 2-3 more days 3. Resume training only when HRV approaches baseline 4. Start with easy sessions regardless
Progressive return: - Day 1 back: 50% of normal volume, low intensity - Day 2-3: Monitor HRV response - If HRV stays stable: gradually increase - If HRV drops: back off, you're not ready
Specific Illness Considerations
Common cold: - Usually resolves in 5-7 days - HRV may recover within a few days of symptom resolution - Light activity often fine once HRV stabilizes
Flu (influenza): - More significant systemic impact - HRV recovery may take 1-2 weeks post-symptoms - Don't rush—flu can progress to serious complications
COVID-19: - Highly variable impact on HRV - Some people recover quickly; others have prolonged suppression - Long COVID can cause months of HRV disruption - Very conservative return to training recommended
Gastrointestinal illness: - Dehydration severely affects HRV - Rehydrate fully before considering training - Usually faster recovery once hydration restored
Post-COVID Considerations
COVID-19 deserves special attention:
Potential concerns: - Myocarditis (heart inflammation) risk - Prolonged autonomic dysfunction - Long COVID symptoms
Conservative protocol: - Minimum 10 days from positive test before exercise - Heart screening if you had significant symptoms - Very gradual return over 2-4 weeks - Stop immediately if you experience chest pain, palpitations, or unusual shortness of breath
HRV monitoring is especially valuable: - Persistently suppressed HRV post-COVID warrants medical evaluation - Some people show HRV disruption for months - Don't push training if HRV isn't recovering
When to See a Doctor
Seek medical attention if: - Fever persists beyond normal illness duration - Symptoms worsen after initial improvement - Chest pain or heart palpitations during or after illness - Extreme fatigue that doesn't improve - HRV remains severely suppressed weeks after illness
Before returning to intense training: - Consider cardiac screening if you had COVID or severe flu - Especially if you're an athlete over 35 - Trust medical guidance over HRV data alone
HRV is a tool, not a diagnostic: - It helps guide decisions but doesn't replace medical care - When in doubt, consult a healthcare provider
Related Guides
- HRV and Overtraining — Distinguishing illness from overtraining
- Getting Started with HRV — Establishing baseline before illness
- Low HRV Guide — Understanding persistently low readings
- HRV Troubleshooting — Other causes of suppressed HRV