Training for Your First Ironman: The Complete Guide to 140.6

What is an Ironman?

An Ironman triathlon is the ultimate endurance challenge: a 2.4-mile (3.8km) swim, followed immediately by a 112-mile (180km) bike ride, and finished with a full 26.2-mile (42.2km) marathon - all completed consecutively within a 17-hour time limit.

The Ironman brand is owned by World Triathlon Corporation, and "Ironman" technically refers specifically to their races. However, the distance (140.6 miles total) has become synonymous with full-distance triathlon regardless of the race organizer.

The first Ironman was held in Hawaii in 1978 with just 15 participants. Today, Ironman hosts over 40 full-distance events annually across the globe, with the Ironman World Championship in Kona, Hawaii remaining the sport's ultimate prize.

Ironman Distances Explained

Triathlon offers a progression of distances. Here's how they compare:

Recommended Progression

Most coaches recommend this progression: Sprint → Olympic → 70.3 → Full Ironman. Each step teaches you new skills and exposes weaknesses before the stakes get higher. Jumping straight to full Ironman is possible but increases DNF risk significantly.

Time Commitment & Prerequisites

Weekly Training Hours

Ironman training typically requires 12-20+ hours per week at peak. First-timers can get away with 12-15 hours if training is structured efficiently. Serious age-groupers and pros train 20-30+ hours weekly.

The time commitment is the biggest barrier. You'll need to swim 3-4 times per week, bike 3-4 times, run 3-4 times, and do strength/recovery work. Some sessions combine disciplines (brick workouts), but the hours add up fast.

Training Timeline

Plan for 20-30 weeks of dedicated Ironman preparation, assuming you have a baseline fitness level. Complete beginners may need 12-18 months to build from zero to Ironman-ready, including shorter races along the way.

Prerequisites

• Ability to swim 1+ mile continuously (any stroke)
• Comfortable cycling 50+ miles
• Can run a half marathon or marathon
• Ideally: 1+ completed triathlon of any distance
• Medical clearance for endurance training

Swim Training

The swim is only 10-12% of total race time but causes the most anxiety for many athletes. Here's how to prepare:

Building Swim Fitness

If you're new to swimming, invest in lessons or a swim coach. Technique matters far more than fitness in the water - efficient swimmers glide while inefficient swimmers thrash. Bad technique can't be out-trained.

Swim 3-4 times per week, with sessions ranging from 2,000-4,000 meters. Include drill work, intervals, and steady-state swims. Your long swim should build to 3,500-4,000m (slightly over race distance).

Pool vs Open Water

Train mostly in the pool for convenience and technique focus, but get regular open water practice. Open water adds challenges: no walls, no lane lines, sighting, waves, currents, and other swimmers. Practice at least once per week in open water during the final 8-12 weeks.

Wetsuit Considerations

Most Ironman swims allow wetsuits (when water temperature permits). A wetsuit provides buoyancy and warmth - it makes swimming easier for most athletes. Buy or rent one and practice in it before race day.

Bike Training

The bike leg (112 miles) takes the most time and has the biggest impact on your run. A well-paced bike sets up a successful marathon; an overly aggressive bike destroys it.

FTP and Power Training

If you have a power meter, use it. Your Functional Threshold Power (FTP) determines your training zones. For Ironman racing, you'll typically ride at 65-75% of FTP - harder than that, and you'll pay on the run.

Without power, use heart rate zones. Check your zones with our heart rate zone calculator and aim for Zone 2-low Zone 3 on the bike.

Long Ride Progressions

Build your long ride to 5-6 hours (100+ miles) in the final 6-8 weeks of training. You don't need to ride the full 112 miles in training - anything over 100 miles provides diminishing returns and increases injury risk.

Bike Fit & Aero Position

A professional bike fit is essential. You'll spend 5-7 hours in the saddle - discomfort compounds over time. If using aero bars, train extensively in the aero position. Your body needs months to adapt to holding that position for hours.

Indoor vs Outdoor Training

Indoor training (trainer/smart trainer) is time-efficient and allows structured workouts. Outdoor training builds bike handling skills and mental endurance for long hours in the saddle. A mix of both is ideal. Check out our cycling training plan generator for structured workouts.

Run Training

The Ironman marathon is unlike any standalone marathon. After 6+ hours of swimming and biking, your legs will feel nothing like they do in training. The key is running off the bike and managing fatigue.

Running Off the Bike

Your legs won't work normally after 112 miles of cycling. Blood has been in your quads, not your running muscles. The first mile or two feels awkward - this is normal. Practice this sensation with brick workouts (more on those below).

Run Volume

Run 3-4 times per week, building your long run to 18-22 miles. Include easy runs, tempo work, and occasional intervals. Most runs should be at easy, conversational pace to allow recovery from swim and bike training.

Use our running pace calculator to set appropriate training paces. Your Ironman marathon will be slower than a standalone marathon - expect to add 10-20% to your typical marathon time.

The Importance of Easy Running

Most of your running should be in Zone 2. Hard running when you're already fatigued from swimming and biking is a recipe for injury and burnout. Save intensity for key workouts.

Brick Workouts

Brick workouts combine two disciplines back-to-back, typically bike-to-run. They're essential for teaching your body to transition between sports and run on tired legs.

Why Bricks Matter

Running immediately after cycling feels terrible - your legs are heavy, your heart rate spikes, and your stride feels off. This is called "brick legs." The more you practice, the faster your body adapts and the less severe the sensation becomes.

Sample Brick Progressions

Do 1-2 brick workouts per week during peak training. The run doesn't need to be fast - it just needs to happen immediately after the bike.

Nutrition Strategy

Ironman nutrition is often called the "fourth discipline." You can be perfectly trained, but if you can't fuel properly, you won't finish.

Race Day Calorie Requirements

Plan to consume 300-400 calories per hour on the bike and 200-300 calories per hour on the run. You'll burn far more than this, but your gut can only absorb so much. The goal is to slow glycogen depletion, not match your burn rate.

Training Your Gut

Your stomach is trainable. Practice race nutrition during every long workout. Figure out what works before race day - experimenting during the race is a recipe for disaster. Many athletes use a combination of sports drinks, gels, bars, and real food.

Bike Nutrition

The bike is where most of your calories come from. You can eat more while cycling than while running. Use liquid calories (sports drink), gels, chews, bars, or even real food. Set a timer to remind yourself to eat every 20-30 minutes.

Run Nutrition

Keep it simple on the run. Cola, gels, and broth are popular choices. Your stomach is more sensitive while running - stick to easily digestible options. Aid stations provide various options; know what you can tolerate.

Hydration & Electrolytes

Drink to thirst but don't overdrink. Take electrolytes (salt tabs, sports drinks) especially in hot conditions. Many athletes use a combination of water and electrolyte drink. Hyponatremia (overhydration) is a real risk in long-course triathlon.

Race Day Execution

Transitions (T1 and T2)

T1 (Swim to Bike): Strip wetsuit, put on bike gear (helmet, shoes, sunglasses), grab bike and go. Practice this in training. Many athletes lay out gear on a towel in a specific order.

T2 (Bike to Run): Rack bike, change shoes, grab run nutrition/hat/sunglasses. Some athletes change socks or clothes entirely - it costs time but may improve comfort for the marathon.

Pacing Strategy

Swim: Start conservatively. Find your rhythm. Don't sprint the first 500m.

Bike: This is where races are lost. Ride at 65-75% of FTP or Zone 2-low Zone 3 heart rate. Resist the urge to go harder - you'll pay for it later. Pass people in the first half; let them pass you. You'll pass them again on the run.

Run: Start slower than you think. Walk through aid stations if needed. The goal is consistent forward progress. Many successful Ironman marathons include strategic walking.

Cutoff Times

Ironman has a 17-hour overall cutoff, with intermediate cutoffs for swim (2:20) and bike (10:30 from race start). Know your cutoffs and pace accordingly. Being conservative early gives you a buffer for problems later.

Sample Training Weeks

70.3 Training (Peak Week)

Full Ironman Training (Peak Week)

Frequently Asked Questions

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