The short answer
Practise night running before a 100K only in safe, familiar conditions. Learn the lamp, footing, layers, navigation, fueling, and decision rules while rested; do not manufacture sleep deprivation to prove readiness.
Ultra-trail fatigue is multifactorial, including physiological, neuromuscular, biomechanical, and cognitive factors.1 Trail-race injury and illness research reports common problems including abrasions, blisters, strains, sprains, gastrointestinal symptoms, and dehydration, while evidence remains heterogeneous.2 Darkness adds a decision and visibility problem that deserves separate practice.
First, read the event
Verify from the official athlete guide:
- when darkness is likely for your pace range;
- mandatory lamps, spare batteries, and reflective gear;
- course marking and navigation rules;
- aid-station and cutoff times;
- crew and pacer rules;
- weather and emergency procedures.
Do not invent a gear list from another race.
A four-session progression
1. Equipment walk
On a familiar, safe path, walk for 20–30 minutes after dark with a buddy. Test lamp fit, beam angle, controls, glasses, layers, and battery access.
2. Short easy run
Run easy on a non-technical route. Practise scanning ahead without staring only at your feet. Stop while attention remains good.
3. Familiar trail loop
Use a known trail with a capable partner and a clear check-in plan. Practise eating, reading markers, changing a battery, and adding a layer.
4. Event-specific rehearsal
Complete a bounded section after sunset inside a normal long-training day. Use race kit and finish early enough that recovery remains part of the plan.
A lamp failure drill
Do this while stationary in a safe place:
- stop moving;
- tell your partner;
- switch to the backup light;
- replace the battery only when footing is secure;
- choose the shortest safe exit if reliable lighting cannot be restored.
Do not continue on a phone flashlight as the primary plan.
Stop rules
Stop or exit when:
- you cannot reliably see footing or course markings;
- navigation errors repeat;
- balance, speech, or thinking becomes abnormal;
- cold, heat, or weather exceeds the plan;
- pain changes gait;
- you become unusually sleepy or confused;
- your partner or event staff tells you conditions are unsafe.
Hallucinations, confusion, collapse, chest pain, fainting, or severe breathing difficulty are not motivation problems. Seek event medical support or emergency help.
Do not train sleep deprivation casually
Being awake all night is not a necessary weekly training stimulus. It can impair attention and increase risk. If the event may extend through the night, practise logistics and a small amount of darkness while protecting normal sleep. Race strategy should include realistic pace, aid time, caffeine decisions, and the possibility of stopping.
Sleep-deprivation reviews report worse endurance, perceived effort, and skill control on average, but ultra-race sleep findings are observational and highly context dependent.4 Reports of falls and hallucinations in long mountain ultras are reasons to plan support and exits, not reasons to rehearse those states in training.5
A worked 90-minute rehearsal
Use this only after the short progression is comfortable and the route is familiar:
| Segment | Job | Decision to record |
|---|---|---|
| 0–20 min | Easy movement before sunset | Did the lamp, layers, and pack stay accessible? |
| 20–50 min | Controlled running after dark | Could you see markers and place your feet without rushing? |
| 50–65 min | Walk-and-fuel block | Could you eat, drink, and navigate without stopping in an unsafe place? |
| 65–80 min | Easy return | Did attention and coordination remain ordinary? |
| 80–90 min | Planned exit and kit check | What failed, rubbed, fogged, or took too long? |
Keep the next day easy enough to reveal the true recovery cost. If normal stairs, balance, concentration, or easy running are worse than expected, repeat a smaller exposure rather than advancing. Ultra nutrition guidance supports practising a tolerable fueling plan before race day, while acknowledging wide individual variation.7
Separate the training plan from the race-night plan
The training plan teaches movement, kit, navigation, and stop decisions. The race-night plan must also use the official course, expected pace, crew access, cutoff math, and event medical procedures. If the event spans more than one night, discuss sleep and caffeine decisions with an experienced coach and the event team; evidence on naps is promising in controlled sport settings but does not create a universal ultra-race protocol.8
Use the 100K trail plan for the full build, the aid-station rehearsal for fuel-and-kit practice, and the ultra cutoff planner for time-buffer decisions.
A pre-run checklist
- charged primary and backup light;
- spare power as required;
- known route and turnaround time;
- buddy/shore contact and check-in;
- weather and trail status;
- visible clothing and required safety kit;
- phone/offline map where appropriate;
- conservative exit option.
Frequently asked questions
How many night runs do I need?
Enough to make equipment and basic movement familiar. Quality and safety matter more than a fixed number.
Should I practise all night?
Not routinely. Practise darkness and logistics without deliberately creating dangerous sleep loss.
Can I run alone on a familiar trail?
A familiar trail can still change at night. Use a buddy or organized setting and follow local safety guidance.
What headlamp brightness do I need?
Follow the event’s rules and test the actual lamp in similar terrain. Beam pattern, battery life, fit, weather, and speed all matter.
This guide is educational, not medical advice. Confusion, fainting, chest pain, severe breathlessness, or an inability to stay warm are reasons to stop and use the event or local emergency plan.
26weeks.ai adapts the training week around the event, completed work, recovery, and real-life constraints. Start training now.
References
- Garbisu-Hualde A, Santos-Concejero J. Limiting factors during an ultra-marathon. 2020. (PubMed)
- Viljoen CT, et al. Injury and illness among trail runners: systematic review. 2021. (PubMed)
- Mauvieux B, et al. Multidisciplinary protocol during a mountain ultramarathon. 2022. (PubMed)
- Lopes TR, et al. Sleep deprivation and endurance performance: systematic review and meta-analysis. 2023. (PubMed)
- Martin T, et al. Sleep patterns and strategies in mountain ultramarathon finishers. 2024. (PubMed)
- Huang M-K, et al. Visual hallucinations in a 246-km mountain ultramarathon: observational study. 2021. (PubMed)
- Tiller NB, et al. ISSN position stand: nutritional considerations for single-stage ultramarathon. 2019. (PubMed)
- Souabni M, et al. Daytime napping and sport performance: systematic review and meta-analysis. 2023. (PubMed)