The short answer
A useful 100K trail drop bag solves a small number of verified checkpoint problems: replacing spent fuel, changing for the next conditions, restoring mandatory kit, and making one fast decision while tired. It should not become a warehouse of untested options.
Start with the current race regulations and athlete guide. Organizers decide which checkpoints accept bags, the permitted bag or weight, deadlines, prohibited items, retrieval after finishing or withdrawal, and whether access is guaranteed. UTMB event regulations show how specific these rules can be: an organizer-issued bag may be required, transport can take time, and early return after withdrawal may not be possible.1 Another race's system is an example, not authority for yours.
Verify the checkpoint before packing
Create a source card from the live organizer documents:
| Question | Verified answer |
|---|---|
| Which checkpoint has the bag? | ___ |
| Organizer bag and size rule | ___ |
| Deposit location and deadline | ___ |
| Expected arrival window | ___ |
| Crew access allowed? | ___ |
| Mandatory kit after the checkpoint | ___ |
| Bag return after finish or withdrawal | ___ |
| Prohibited contents | ___ |
Save the document edition and the date you checked it. Recheck during race week because weather rules, transport, cutoffs, and mandatory equipment can change.
Do not place identification, essential medication, valuables, or the only copy of something irreplaceable in a bag unless the organizer explicitly instructs you to do so. A drop bag can be delayed, misrouted, exposed to weather, or inaccessible after a withdrawal.
Pack by the next section's job
Lay out the course from the checkpoint forward. Ask what will change before the next reliable support:
- daylight to darkness;
- warm valley to exposed ridge;
- dry conditions to forecast rain;
- long runnable section to a steep hiking section;
- fuel supply after several hours of accumulated intake;
- mandatory-kit check;
- known foot or chafing routine.
Then choose the minimum tested response. “Cold after sunset” might mean one labelled dry layer and gloves. It does not automatically mean four jackets. “Fuel restock” means counted, familiar servings mapped to the next aid points, not every flavor in the cupboard.
Ultramarathon nutrition guidance supports individual, practiced plans and recognizes that gastrointestinal tolerance, environment, pace, duration, and food availability vary.3 It does not validate a universal drop-bag menu. Use products and quantities already tolerated in long training.
Use modules, not a loose pile
Pack transparent, labelled modules:
- Next-section fuel: counted servings plus a small event-legal contingency.
- Fluids and mix: exact powder portions with concentration written on the label.
- Weather change: one tested layer set for the forecast decision.
- Feet and friction: only the items you know how and when to use.
- Mandatory kit: the verified replacement or addition, if rules allow.
- Waste exit: a resealable bag for used packaging and wet items.
Put the likely module on top. Number the order on a card inside the lid: refill, eat, layer, waste, leave. Under fatigue, sequence beats choice.
Keep liquids isolated and double-bag powders. Mark the outside exactly as the organizer requires. Add your race number in the permitted format rather than inventing a label that covers official identification.
Build a checkpoint decision card
The bag should support decisions, not make them for you.
| Check | Green | Amber | Red |
|---|---|---|---|
| Temperature and weather | expected | changing sooner than expected | official severe-weather instruction |
| Fuel tolerance | plan working | mild symptoms, intake needs simplifying | repeated vomiting or cannot keep fluid down |
| Feet and movement | normal | early hotspot or minor friction | injury changes gait or normal movement |
| Alertness | ordinary fatigue | slowing decisions or unusual sleepiness | confusion, collapse, or unsafe coordination |
| Cutoff | rehearsed buffer intact | buffer shrinking | follow official withdrawal instruction |
In amber, simplify. Take the already-tested response, reduce choices, and tell event support when appropriate. In red, the race plan stops being the priority.
Exercise-associated hyponatraemia is a serious risk, so more drink is not automatically safer.4 Do not use a drop bag to catch up by consuming an untested amount of fluid or sodium. Likewise, a bag cannot fix dangerous heat exposure; heat guidance combines preparation, pacing, cooling, and event medical controls rather than one product.5
Rehearse the complete stop
Use one long-run checkpoint simulation three to five weeks before the event, when recovery time remains.
- Give the bag to a partner or place it at a permitted loop point.
- Approach after several hours, not while fresh.
- Start a timer when you enter the stop.
- Follow the exact card without discussing new options.
- Refill and repack waste using cold, wet, or gloved hands if relevant.
- Leave for a section that resembles what follows on race day.
- Record time stopped, what was unused, and what was hard to find.
The objective is not the shortest possible stop. It is a controlled, repeatable stop that completes the next section's job. If a two-minute saving creates a missed layer or incorrect drink concentration, it is not efficiency.
Use the 100K aid-station rehearsal to practise the wider sequence and the ultra cutoff planner to keep stopped time visible.
Rehearse the missing-bag plan
Assume the bag is not immediately available. Your baseline carried kit must still meet the current rules and keep you safe between official support points. Write one fallback:
- use on-course food already tested;
- refill with the verified aid-station option;
- keep the essential weather layer on your body or in your mandatory carry;
- ask officials where to report a missing bag;
- continue only if doing so remains safe and rules-compliant.
Do not hide required equipment in a future bag if it must be carried from the start. Do not accept unauthorized outside assistance because the planned bag is missing.
Long races also involve sleep loss and accumulated fatigue. Athlete sleep guidance supports protecting pre-event sleep opportunity, but it does not make a drop-bag stimulant or supplement universally safe.6 Avoid introducing medication, supplements, or unfamiliar caffeine at the checkpoint. Medical and anti-doping questions need qualified, event-specific advice.
Race-week packing pass
Forty-eight to seventy-two hours before bag deposit:
- re-open the current official documents;
- check forecast-triggered kit changes;
- count every serving against the next-section timeline;
- inspect batteries and permitted electronics without relying on them as the only safety system;
- photograph the contents and official label;
- seal wet-sensitive modules;
- remove valuables and untested products;
- tell crew what they may and may not do.
Long-haul travel can disrupt sleep, routine, and access to familiar food.7 Pack the checkpoint modules before travel where practical, but keep final organizer verification separate so an early packing decision does not override new instructions.
Frequently asked questions
How many drop bags do I need for a 100K?
Use only the locations the organizer offers and the course problems you can name. One well-rehearsed bag may be more useful than several bags full of choices. Some events provide none; your carried mandatory kit and official aid plan must work without assuming a bag exists.
Should I put spare shoes in a drop bag?
Only if the rules allow it and you have a rehearsed reason to change. New or rarely used shoes can create different pressure and friction. A shoe change is an option, not a treatment for severe pain or an injury that changes normal movement.
How much extra fuel should I pack?
Map familiar servings to the time until the next reliable supply, then add a small, event-legal contingency based on your rehearsal. Do not pack an unbounded amount or use the stop to compensate with a large, unfamiliar intake.
What should I do if my bag is missing?
Tell the official checkpoint team and use the fallback you rehearsed. Follow the organizer's assistance and withdrawal rules. Do not continue into unsafe conditions or accept prohibited support merely to preserve a finish attempt.
Safety boundary
Stop and seek event medical support for confusion, collapse, fainting, severe breathing difficulty, chest pain, repeated vomiting, inability to keep fluid down, dangerous cold or heat symptoms, or an injury that changes normal movement. Follow the organizer's withdrawal and transport procedure.
This guide is educational and not medical advice. It cannot determine whether continuing is safe or whether a food, medicine, supplement, footwear change, or foot-care intervention is appropriate for you.
26weeks.ai keeps 100K training, long-run rehearsals, recovery, and the finish line in one adaptive flow. Start training now.
References
- UTMB World Series. Eiger Ultra Trail by UTMB 2026 regulations. (Official regulations)
- UTMB World Series. KAT100 regulations and drop-bag rules. (Official regulations)
- Tiller NB, et al. International Society of Sports Nutrition position stand: nutritional considerations for single-stage ultra-marathon training and racing. 2019. (PubMed)
- Hew-Butler T, et al. Exercise-associated hyponatremia consensus statement. 2018. (PubMed)
- Racinais S, et al. Consensus recommendations on training and competing in the heat. 2015. (PubMed)
- Walsh NP, et al. Sleep and the athlete: expert consensus recommendations. 2021. (PubMed)
- Fowler PM, et al. Long-haul travel, recovery, and performance in elite athletes: systematic review. 2022. (PubMed)
- Li S, et al. Recovery strategies in endurance athletes: umbrella review. 2024. (PubMed)