Trail Running Race Planner

1. Route & pace setup

0% even effort50% (22% 2nd half)100% (40% 2nd half)
GAP pace rises in a straight line with distance, from the start to the finish. In brackets: how much slower the second half is than the first, on average.
Load a GPX to see the GAP pace needed for your target time.

2. Aid stations

Aid stations split the race into the segments used for targets, fuelling and packing. Remove one with the X in the segment table.

3. Physiology & energy expenditure

Typical 0.15–0.25 (more with heavy downhill muscle damage)
Adds to the energy cost in proportion to body weight
Caps your speed on descents; slows the plan where GAP would be faster
Gut & GI distress model
Most you absorb when rested and cool. Also the max intake of the GI plan.

Muscle mass is estimated as ~55% (men) / ~50% (women) of lean body mass. Each gram of glycogen holds ~2.7 g of water. Energy burned = zone kcal/h at your GAP pace × temperature multiplier × (1 + drift × km) × (body + pack) ÷ body mass. Multiplier: 1.0 between 5–15°C, +1% per °C above 15°C, +1.5% per °C below 5°C. The CHO share also shifts: +1.0 pt per °C above 15°C, +0.5 pt per °C below 5°C. Effort for the GI model is placed between your VT1 and VT2 paces.

Do the tests ↗

Enter values from a lab test or your watch. The GAP pace of each zone links it to the course: the plan’s GAP pace at every point is placed between your zones and the burn is interpolated. Heart rate is for your reference. Imported zones (Test 1 / 1b) are run at 10% grade: their GAP pace is the treadmill speed made flat-equivalent with the GAP formula below.

GAP formula
Do the GAP test ↗

4. Hydration settings (L/h by temperature)

Expected fluid loss by the forecast temperature of each segment.

The fuelling plan aims to replace this much sodium for every litre you drink. Don’t know yours? Pick “Normal”.

At 0 the plan replaces all the sweat you lose (your L/h above).

Above 0, every segment’s fluid target is lowered by the same share so the body estimate at the finish lands at this weight loss. It counts sweat, metabolic water, glycogen and fat used. Losses above ~2–3% are commonly linked to lower performance; above ~4% to health risk.

Sunrise: –:–
Sunset: –:–
Daylight status: Upload GPX to calculate

5. Elevation profile

Hover (or tap) the profile for time, distance, altitude, gradient, daylight, weather, wind and calories burned so far.

6. Segment strategy & environmental breakdown

Carbs/h on every segment start at the CHO you burn there (no cap), from your physiology, pace and weather. Type a value to set your own; tap 🔥 to go back to the burn.
Aid stationDist (km)ETASeg distSeg timePace real / GAP Gain / loss (m)Weather forecastCarbs (g/h)Target carbsTarget fluid

7. Caffeine plan

Choose where to take caffeine by km or by time of day (the other updates from your pacing). Caffeine kicks in after ~30–45 min.

KmTime of dayDose (mg)mg/kgLasts (h)Active windowSegment

8. Course sections

The GI model splits the route into climbs, descents and rolling sections. Time, speed, effort and CHO burned in each section come from the plan above.

9. GI distress profile

SafeHigh loadOverload

Risk uses each segment’s carbs/h from the strategy table (your burn, unless you changed it), or a section’s own carbs/h once you edit it or apply a compensation. Tap a section to jump to it.

10. Plan priorities

    11. Sections

    12. GI race nutrition plan

    Follows only what you burn: no extra eating before risky stretches. Each intake is sized from what you’ve burned and not yet eaten (no ceiling, so a shortfall stays owed until it can be eaten safely) plus what you’ll burn in the next 30 min, up to your trained gut capacity. It is placed at the lowest-risk moment in those 30 min: before descents, at the bottom of them, low on climbs, once cooled. Products come from your library.

    –

    Gels count in full at once. Solid food is released over 25 min and only placed on easy, non-descending stretches with SpO₂ ≥ 90% and core ≤ 38.6 °C, at most every 2 h. Nuts are for fat in races over 6 h, at most every 3 h.

    13. GI nutrition plan: profile and hours

    Intakes on the profile
    Gel (size = grams)Solid foodNuts Gut capacity highReducedLow
    Per hour
    CHO burnedCHO plannedAbsorbable (80% of capacity)Fluid (ml)

    14. Fuelling & hydration plan per segment

    Each segment shows what you burn, the target from the strategy table and the GI plan’s proposal. Add the proposal with one tap, then adjust products and flasks. Drink mixes are scaled to the flask volume (a 0.25 L flask of a 500 mL mix = half a serving).

    15. Race totals

    16. Packing list

    ItemQuantity

    17. At the finish — body estimate

    If you eat and drink exactly what’s planned above.

    Water balance = drunk + metabolic water (0.6 g per g CHO and 1.07 g per g fat burned) − sweat (your L/h at the forecast temperature). Water released from glycogen (2.7 g per g) stays in the body and offsets part of the deficit, so “true” dehydration is smaller than the weight loss suggests. Fat loss = fat burned − fat eaten. Below 3.5% body fat for men (12% for women) the estimate turns orange.

    18. Product library — edit nutrition values or add your own food & drinks

    Food values are per unit (one gel, one sandwich…). Drink values are per serving mixed in the given volume. Brand values come from manufacturer listings where available, but formulas change — check your labels and edit.

    BrandProductTypeMix vol (mL)kcalCarbs (g)Sodium (mg)Fat (g)Caffeine (mg)