The traditional “symptoms below the neck” rule (rest if you have chest congestion, body aches or stomach issues, but train if symptoms are limited to a runny nose or sore throat) remains a simple starting point for cyclists deciding whether to ride or rest. It’s grounded in the idea that systemic symptoms (like fever or muscle pain) signal a more serious immune response, while mild upper respiratory issues may not pose the same risk. However, while this rule offers a basic guideline, using more modern tools gives you a more nuanced and accurate way to assess your body’s readiness.
HRV is your body’s early warning system
HRV measures the variation in time between heartbeats, reflecting your autonomic nervous system’s balance. When you’re getting sick, HRV often drops 1-3 days before symptoms appear. A sudden decrease of 10 to 15% in your baseline HRV signals stress from overtraining, poor sleep or illness. The good news is that most smart watches can track HRV these days, so most cyclists have access to this metric.
What to watch for:
- HRV drops below your seven-day average by 10% or more.
- HRV remains low for two or more days without an obvious cause.
- HRV fails to rebound overnight, even after a rest day.
If your HRV is trending downward and you feel off, swap intensity for volume or take an extra rest day. Ignoring these signs often leads to a longer setback.
Skin temperature can be a subtle but telling sign
Another thing that many wearables track is skin temperature. It can rise slightly 24 to 48 hours before you feel feverish. A spike of 0,5 to 1°C above your baseline can signal an immune response. Also, temperature spikes after a hard workout indicate that your body is struggling. It’s another metric you can check out if you have a suspicion that something may be off.
If your temperature is elevated and you’re fatigued, skip high-intensity sessions until it normalises. Light activity is fine, but avoid pushing hard.
Staged return-to-play protocol
One of the biggest mistakes cyclists make is jumping back into hard training too soon after illness. Sports medicine uses staged return-to-play protocols to avoid relapses.
Stage 1: Total rest (systemic symptoms present)
- No training if you have a fever, body aches or fatigue.
- Focus on hydration, sleep, and easy nutrition.
- Monitor HRV and temperature daily. Wait until both return to baseline before progressing.
Stage 2: Light activity (symptoms gone, HRV/temperature normal)
- 10 to 20 minutes of zone 1 riding.
- No group rides or high-intensity efforts.
- If you feel fine the next day, repeat or extend to 30 minutes.
Stage 3: Moderate volume (2 to 3 days symptom-free)
- 30 to 45 minutes of zone 2 riding at a conversational pace.
- Check HRV and temperature before and after. If either dips or spikes, go back to Stage 2.
Stage 4: Resume intensity (5+ days symptom-free, HRV stable)
- Short, controlled intensity, such as 2×5 minutes at threshold with full recovery.
- No races or all-out efforts until you’ve completed a full week of symptom-free training.
- Listen to your body. If you feel unusually fatigued, dial it back.
Key principle: No catching up. Trying to make up lost training by overloading post-illness risks relapse or injury. Accept the training loss and adapt your training plan to reflect it.
Illness as part of the process
Getting sick isn’t a failure; it’s a normal part of training through winter. The goal isn’t to avoid illness entirely but to manage it smartly so it doesn’t derail your season. Athletes who modify their plans to minimise the risk of illness and follow the right protocol to return to cycling do much better in the long-term. Remember, one week of cautious training is better than three weeks off from a relapse.
