Strava and Garmin integration
Workouts pull in automatically with duration, distance, intensity. Symptoms get correlated.
- Strava sync
- Garmin Connect sync
- Apple Health
For athletes
Solve the race-day belly.
Up to 70% of endurance athletes have GI symptoms during training. A Gut Day cross-references your fuelling, intensity and gut response so you can find the combinations that work.
Why athletes get gut symptoms
During hard endurance work, blood diverts away from the gut to the muscles. This causes ischaemia, slowed motility and increased intestinal permeability - the cocktail behind cramps, urgency and runner's diarrhoea. The trigger combinations are personal: a gel that works at marathon pace might fail at threshold. A Gut Day finds your specific fuelling sweet spot.
Built for endurance athletes
Pre-workout fuelling log
Time, type and grams of carbs before each session. The app correlates with mid-workout symptoms.
In-workout nutrition
Gels, drinks, real food. Tag intensity zone. The app shows what tolerates at threshold vs Z2.
Race-day playbook
After a few months of data, the app generates your personal race-day fuel protocol.
How A Gut Day helps
Built for this exact problem
Gel and drink database
All major sports nutrition brands tagged with carb type, ratio and FODMAP profile.
- Maurten, SiS, Gu, Tailwind, etc.
- Carb-ratio tracking
- FODMAP flags
Carbs-per-hour calculator
Tracks your in-session carb intake and flags when you exceed your gut-trained ceiling.
- Live carb tally
- Per-hour rate
- Tolerance ceiling alert
Pre-race protocol generator
Based on what worked, the app builds your race-morning meal, breakfast timing and warm-up snack.
- Personalised timing
- Carb-load support
- Bathroom-window prediction
How A Gut Day works for athletes
- 1
Connect your training app
Strava, Garmin or Apple Health. Workouts sync automatically with duration and intensity.
- 2
Log fuel and symptoms per session
What you ate before, during and after. Stomach symptoms during the workout.
- 3
After 6 to 8 weeks: see your patterns
The app shows which gels/drinks/timing combinations cause issues, and which are safe.
- 4
Build your race-day plan
The app generates a tested protocol you can stick to on race day.
Why fructose-glucose mixes matter
Pure glucose hits an absorption ceiling around 60g/hour. Adding fructose at a 2:1 ratio (glucose:fructose) lifts that ceiling to 90g/hour because fructose uses a different transporter (GLUT5).
But some athletes have lower GLUT5 expression and get cramps from high-fructose products. A Gut Day's gel database tracks the carb ratio of every product so you can see whether 2:1 or 1:0.8 actually works for you.
Gut training - it is a real thing
The gut adapts to carb load with training. Athletes who repeatedly fuel with 90g/hour over 8 to 12 weeks can lift their ceiling without symptoms. Without the protocol, sudden race-day high-carb plans almost always fail.
The app tracks your weekly carb ceiling and progresses it gradually - the gut equivalent of base-building.
Frequently asked questions
- Is this only for runners?
- No - cyclists, triathletes, ultra-runners and rowers all get GI issues. The app is sport-agnostic.
- Will it tell me what gels to use?
- It will tell you which gels you tolerate, based on your own data. We do not partner with any brand.
- Can it help with low-carb / fat-adapted athletes?
- Yes - if you fuel mostly with fat, the app tracks fat type and correlates with reflux/heaviness, the more common low-carb gut issue.
- Does it work for daily training, not just races?
- Yes - many users solve their daily 'first 30 minutes' bathroom anxiety with regular tracking, before they ever think about race day.
- What about hydration and electrolytes?
- Tracked. Sodium intake and fluid balance are key drivers of cramp risk.
Stop guessing your race fuel
Free Strava/Garmin sync, gel database and personal race-day protocol generator.
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