Ultramarathon Beginner’s Guide: Transitioning from Marathon to 50K/100K

Once you’ve finished several full marathons and start feeling that 42.195 kilometers is no longer the finish line but the starting point of another journey—congratulations, the door to ultramarathon running is opening for you. This article will walk you through the training transition strategies from marathon to 50K, and even 100K.

What Is an Ultramarathon?

An ultramarathon refers to any running event exceeding 42.195 kilometers. Common distances include:

• 50K: Entry-level ultramarathon, about 8 km longer than a full marathon
• 100K: Classic ultramarathon distance, requiring 8-14 hours
• 100 miles (161K): The “Holy Grail” of ultramarathons
• Timed events: 12-hour, 24-hour, 48-hour

Classic Ultramarathons in Taiwan

Event	Distance	Highlights
Soochow International Ultramarathon	24 hours	Taiwan’s longest-running ultramarathon, held on a 400m track
Yangmingshan Ultramarathon	50K / 100K	Trail running with cumulative elevation gain exceeding 3,000m
Taroko Gorge Marathon	Full marathon (can serve as an ultramarathon precursor)	Spectacular canyon terrain, ideal for practicing mountain endurance
Southern Cross-Island Ultramarathon	100K	Crosses the Central Mountain Range with extreme elevation changes
Around Hualien-Taitung Ultramarathon	333K (multi-stage)	Taiwan’s most iconic multi-day ultramarathon

From Marathon to Ultramarathon: A Shift in Training Mindset

Redefining Your Pacing Concept

Marathon runners are used to measuring performance by “pace,” but in the ultramarathon world, “finishing” is itself the victory.

Distance	Estimated pace for sub-4 marathoner	Estimated finish time
50K	6:00-6:30/km	5-5.5 hours
100K	7:00-8:00/km	11-14 hours

Your pace will be much slower than your marathon pace—and that’s perfectly normal. The key to ultramarathons isn’t “how fast you run,” but “how slowly you endure.”

Heart Rate Control

In ultramarathon training, heart rate control matters more than pace:

• Long runs: Keep heart rate in Zone 1-2 (60-72% of max heart rate), approximately 120-145 bpm
• First half of the race: Strictly stay below Zone 2
• Middle to later stages: Slow down appropriately as cardiac drift occurs

Building Training Volume

Recommended Weekly Mileage

Target distance	Recommended weekly mileage	Longest single run
50K	60-80 km	30-35 km
100K	80-120 km	40-50 km (or back-to-back long runs)

16-Week 50K Training Overview

Weeks 1-4 (Base Phase):

• Weekly mileage: 50-60 km
• Long run gradually increases to 25 km
• Pace: Zone 2 throughout

Weeks 5-8 (Accumulation Phase):

• Weekly mileage: 60-75 km
• Long run reaches 30 km
• Add back-to-back long runs (Saturday 20km + Sunday 15km)

Weeks 9-12 (Intensification Phase):

• Weekly mileage: 70-80 km
• Long run reaches 35 km
• Practice race-day fueling strategies

Weeks 13-16 (Taper Phase):

• Weekly mileage gradually decreases to 40-50 km
• Final long run completed 3 weeks before race day

Back-to-Back Long Runs

This is the signature technique of ultramarathon training. Running long on consecutive days simulates accumulated fatigue:

• Saturday: 25-30 km @ 5:30-6:00/km
• Sunday: 15-20 km @ 6:00-6:30/km

The feeling of running on fatigued legs on Sunday closely mimics the physical state in the latter half of an ultramarathon.

Ultramarathon Fueling Strategy

One of the biggest differences between marathons and ultramarathons is fueling. In a marathon, you might get by with 3-4 energy gels, but ultramarathons require a more complete nutrition plan.

Hourly Fueling Targets

• Calories: 200-300 kcal/hour
• Fluids: 500-800 ml/hour (adjust based on temperature)
• Electrolytes: 300-600 mg sodium per hour
• Carbohydrates: 60-90 grams/hour

Fueling Options

Type	Examples	Advantages	Best Used
Energy gels	GU, SIS, Maurten	Rapid absorption	Early stages, when quick energy is needed
Solid food	Rice balls, bananas, sweet potatoes	Strong satiety	Middle to later stages, at aid stations
Liquid fuel	Sports drinks, cola	Hydrates and fuels simultaneously	Throughout the race
Salty food	Salty congee, miso soup	Replenishes sodium, warms the stomach	Nighttime, cold conditions

Taiwan ultramarathon tip: Many runners bring braised snacks or pork floss rice balls to 100K races, and some aid stations even serve hot noodle soup. Training your gut is just as important as training your legs!

Gut Training

Gastrointestinal issues are one of the most common reasons for DNF (Did Not Finish) in ultramarathons. Recommendations:

• Simulate race-day fueling during long runs
• Find out which food combinations work for you
• Avoid trying new foods on race day
• Practice eating solid food while running

Gear Selection

Essential Gear

1. Running shoes: Choose well-cushioned models; ultramarathons don’t require lightweight racing shoes
2. Hydration vest/bottles: A vest capable of carrying 500ml-1.5L
3. Headlamp: 100K races almost always extend into darkness; at least 200 lumens
4. Anti-chafing: Petroleum jelly or specialized anti-friction balm applied to armpits, groin, and toes
5. Spare clothing: A light jacket for nighttime temperature drops

Foot Care

Blisters are the biggest fear in ultramarathons. Preventive measures:

• Wear socks tested in long runs (toe socks recommended)
• Apply petroleum jelly between toes
• Carry spare socks to change at aid stations
• Choose shoes half a size larger to accommodate foot swelling

Mental Preparation

An ultramarathon is a mental battle. Here are insights from those who’ve been there:

The “Segment Thinking” Strategy

Don’t think “I still have 60 km to go.” Instead, break the race into smaller segments:

• 100K = 10 x 10K
• Reaching each aid station is a small victory

The “Low Points Always Pass” Rule

Almost every ultramarathon runner experiences at least one low point during a race—muscle soreness, wanting to quit, questioning why you’re even there. Remember: Low points pass; push through and there’s a new horizon on the other side.

The Run-Walk Strategy

You don’t need to run the entire ultramarathon! Run-walk alternation is a completely normal and smart strategy:

• Walk uphill, run downhill, run on flats
• Or use a fixed ratio: run 10 minutes, walk 1 minute

Start with Your First 50K

If your marathon finish time is between 4-5 hours, you already have the base fitness to take on a 50K. Give yourself 16-20 weeks of preparation, pick a local ultramarathon in Taiwan, and begin your ultramarathon journey.

Remember the famous saying in the ultramarathon world: “An ultramarathon isn’t a race of who runs fastest—it’s a race of who slows down most gracefully.”

Related Reading

• Ultramarathon Beginner’s Guide: Crossing the Training Volume from Marathon to 50K
• Ultramarathon Beginner’s Guide: Mileage Transition Strategy from Full Marathon to 50K
• Long-Term Planning for Ultramarathon Preparation: Mileage Accumulation Strategy Over 6+ Months
• Taiwan Ultramarathon Race Calendar: Complete List of Major Ultramarathon Races