Setback Strikes: How to Train for a Marathon When You’re Sick?

Getting sick has been one of the biggest hurdles for me getting back in shape. I get a surge of motivation, start training, get sick, wait till I get healthy, and….. nothing.

The surge of motivation is gone. The momentum I built is dead, and I wait for a new surge of motivation.

Not this time. When getting my week 2 plan, I told my AI coach that I was developing a sore throat.

The response was golden:

This is classic “Neck Check Pass” territory - symptoms above the neck, no fever, functional but not great.

You can train lightly, but this week needs to be about maintaining the habit without digging a deeper hole.

Run 1 (earliest when throat feels okay):

3km easy, focus on just moving gently

• Nose-breathing ONLY. If you can’t maintain nose breathing, you’re going too hard.
• Heart Rate Cap: Stay under 135 bpm average. If it climbs to 140+, walk for 1-2 minutes.
• Walk breaks: Take them liberally. 1 minute walk every 5-7 minutes is smart, not weak.
• CRITICAL: The “Quit Mid-Run” Rule*. If your heart rate won’t stay below 140 despite slowing down → stop and walk home

MOBILITY: Daily, But Gentle

10-15 minutes daily - This actually HELPS recovery

Focus:

• Gentle hip flexor stretches
• Light foam rolling (calves, IT band, glutes)
• Easy yoga flows or dynamic stretching
• Nothing intense, just movement to aid circulation

Why continue mobility:

• Promotes blood flow without stress
• Maintains flexibility during reduced training
• Active recovery for your nervous system

And that’s it. That’s how I maintain momentum with my marathon training despite getting sick.

Wearable Data as an Early Warning System

Looking back, my AI coach could connect the puzzle pieces and “predict” the illness. Here’s what it told me about my week 1:

1. Volume Overshoot: You ran 16.5km vs planned 12km (38% more)
2. HRV Trend: Dropped from 77 (assessment) to 66 average (shows accumulated fatigue)

….

• Upper respiratory infections often follow 7-10 days of accumulated training stress
• Your HRV drop (77→66) predicted this - body was already stressed
• Running volume increase + life stress + immune system overwhelm = current state

The interesting question is, could my coach have actually predicted the illness?

There’s some research done on this topic. E.g., one study looked at 200,000 Fitbit wearers in five US states, and studied whether the data could predict influenza-like illnesses.

The results were promising: “We found the Fitbit data significantly improved ILI (influenza-like illness) predictions in all five states…”

https://pmc.ncbi.nlm.nih.gov/articles/PMC8048388/

My coach doesn’t yet get daily data for analysis, but this tells me it probably should.

Maybe it can catch an illness and help me adjust in time. One thing is for sure, I’ll be looking into this.