Most triathletes treat the bike leg like filler. They swim, they run, and then whatever time is left over goes to the bike — done at whatever intensity feels vaguely right on the day. No structure, no periodisation, no real plan.
Here's the thing: the bike leg is where races are won and lost. It's the longest discipline by time. It's where you set up your run or destroy it. And it responds brilliantly to structured, cycling-specific training that most triathletes never bother with.
When Olav Bu came on the podcast to discuss how he coaches Kristian Blummenfelt and Gustav Iden, one of the first things he said floored me. He doesn't start with physiology. He starts with the athlete's psychology — what pulls them to train versus what pushes them. As he put it: "What you're really committing to is the process getting to the goal because the goal is just like a minor energy consumption or dot in your calendar compared to all the process." That mindset shift changes everything about how you approach the bike.
Why Triathlon Bike Training Is Different
Pure cyclists can afford to hammer every ride. They recover, adapt, go again. Triathletes can't. You're managing fatigue across three disciplines, which changes everything about how you approach the bike.
The biggest difference: recovery cost. A hard 90-minute threshold session on the bike doesn't just affect your next ride — it affects tomorrow's swim and the run session the day after. Every session has a knock-on effect across the whole week.
When Alistair Brownlee sat down with us, he was blunt about this. The two-time Olympic gold medallist said the key to his cycling wasn't doing more bike training — it was doing the right training and protecting recovery for the other disciplines. He specifically warned against chasing zone precision: "Being way below the top of Zone 2 matters far more than nailing exact wattage — riding at 250W or 295W produces similar adaptations but the latter carries much higher fatigue risk that compounds over time."
That's a man with two Olympic golds telling you to calm down on the bike. Listen to him.
Dan Lorang, head of performance at Red Bull-Bora-Hansgrohe and Roglic's coach, reinforced this when he came on the show. He told us: "It's not about the one key session, about one big day that you have to do. It's more about giving your body constantly a certain amount of load." For triathletes managing three sports, that principle of consistent load management is even more critical than it is for pure cyclists.
The Polarised Approach for Multi-Sport Athletes
If the polarised training model works for single-sport athletes, it's even more critical for triathletes. The principle is simple: 80% of your training at genuinely easy intensities, 20% at genuinely hard intensities, and as little as possible in the grey zone between.
Professor Seiler came on the podcast twice and both times hammered the same point: establish frequency first, then duration, and only introduce intensity after a solid aerobic base exists. He told us the order most amateurs follow — going hard from day one — is exactly backwards. His research across thousands of elite endurance athletes shows the 80/20 distribution works regardless of whether you're targeting a criterium or an ultra-endurance event.
For a triathlete doing 10 hours of cycling per week, that means roughly 8 hours of pure Zone 2 riding and 2 hours of quality work — threshold intervals, VO2max efforts, or race-specific sessions.
The Zone 2 rides build your aerobic engine without eating into your recovery budget. The quality sessions push your ceiling higher. The grey zone — riding at tempo because it "feels like training" — just accumulates fatigue without enough stimulus to justify the cost. Seiler called it clearly: "If you're in a hole, the best thing to do is stop digging."
Structuring Your Bike Training Week
Olav Bu's approach to structuring training for Blummenfelt and Iden is to work backwards from race day, not forwards from today. He identifies the gap between where the athlete is (point A) and where they need to be (point B), then quantifies exactly what's needed to close it. He uses quarterly assessments — treating training load like business accounting, as he described it — to see where resources are being wasted and where the best returns are.
You don't need a Norwegian national team budget to apply this. Here's a practical framework for a triathlete training 8-10 hours on the bike per week:
Key Session 1 (Tuesday or Wednesday): Threshold intervals. Something like 3x15 minutes at 90-100% FTP with 5-minute recoveries. This is the session that raises your FTP and directly improves bike leg performance.
Key Session 2 (Saturday): Long ride with race-specific efforts. 3-4 hours with 2x20 minutes at target race power baked in. This teaches your body to sustain race intensity on fatigued legs.
Everything else: Genuine Zone 2. Easy spinning that builds aerobic fitness without compromising your swim and run sessions. If you're breathing hard, you're going too hard. Seiler's research shows that ventilation — your breathing rate — is actually a better real-time indicator of effort than heart rate or lactate. If you can't hold a conversation, you're not in Zone 2.
Brick Sessions: Less Is More
Every triathlete knows about bricks. Most do them wrong — either too often or too intensely.
One brick per week is enough. The purpose isn't to accumulate extra volume. It's to teach your neuromuscular system to handle the bike-to-run transition. Your legs feel like concrete for the first kilometre off the bike, and the only way to manage that sensation is to rehearse it.
A good brick: 75-90 minutes on the bike at a steady effort, followed immediately by a 15-25 minute run. The run doesn't need to be fast. Just get off the bike and run at your planned race pace. That's it. The adaptation is neurological, not physiological.
Ben Hoffman, six-time Ironman champion, made a point on our show that most triathletes need to hear: "The equation is simple — stress plus rest equals growth. Most athletes get this wrong by overtraining while underestimating life's accumulated stressors." He's talking about the financial pressure, the family commitments, the social media doomscrolling at midnight. All of that is stress your body has to recover from. Stacking bricks on top of everything else is often the straw that breaks the camel's back.
Managing Fatigue Across Three Disciplines
The single biggest mistake triathletes make with cycling training is ignoring cumulative fatigue. A 5km hard run on Monday generates fatigue that's still present when you ride on Tuesday. A hard swim on Wednesday affects your threshold session on Thursday.
Olav Bu treats training like energy accounting: "You can't create and you can't destroy energy, you can only convert energy from one form to another form — and that's why I'm very careful about causing too large deficits over longer periods." He's not just talking about nutrition. He's talking about the total energy cost of training across all disciplines.
Practical rules:
- Never schedule two hard sessions on consecutive days across any discipline. A hard ride Tuesday means an easy swim or rest on Wednesday.
- Put your most important session earliest in the week when you're freshest. If the bike is your limiter, your key cycling session goes early.
- Protect the long ride. Your Saturday or Sunday long ride is the single most important cycling session of the week. Don't arrive at it fatigued from a hard run the day before.
- Track total training stress, not just cycling stress. Use a tool like Training Peaks to monitor load across all three sports. Your body doesn't care which discipline the fatigue comes from.
Dan Lorang gave us a brilliant framework for this: plan your full week — work, family, sleep, appointments — before building your training plan. As he said, professionals hand their calendar to their coach so load is managed holistically. Amateurs should do the same.
When to Prioritise the Bike
If your swim is solid and your run is competent, the bike is almost certainly where you'll gain the most time. A 5-watt increase in FTP over a 90km bike leg saves roughly 2-3 minutes. That's an enormous gain for a few weeks of targeted training.
During your build phase, consider temporarily reducing swim volume to protect bike quality sessions. You won't lose meaningful swim fitness in 6-8 weeks of maintenance swimming, and the bike gains will more than offset it.
Olav Bu's core principle for Blummenfelt and Iden applies directly here: the best endurance athletes don't try to be equally good at everything simultaneously. They periodise — focusing on one limiter while maintaining the others. As he put it: "I don't have a determination of what and how, it comes more down to where do we think is the most to be improved compared when we look at the gap."
Brownlee backed this up with typical bluntness: "Don't be distracted by the minor sometimes — make sure you fundamentally do the training because that's the 95% of it, and then the rest of it is the small stuff."
Key Takeaways
- The bike leg is where triathlon races are won and lost — give it the training volume it deserves
- Use the polarised approach: 80% Zone 2, 20% quality sessions, minimal grey zone
- Structure your week around 2 key cycling sessions plus Zone 2 volume
- One brick session per week is enough — the adaptation is neurological, not just physiological
- Manage fatigue across all three disciplines, not just cycling in isolation
- Know your FTP zones and use the FTP Zone Calculator to govern every session
- During build phases, consider temporarily reducing your weakest discipline to protect bike gains
Frequently Asked Questions
How many hours per week should a triathlete spend cycling?
For a competitive age-grouper targeting a 70.3 or Ironman, aim for 6-10 hours of cycling per week during build phases. The bike leg is where the most time is gained or lost, so it should receive the largest training volume of the three disciplines — typically 45-55% of total training time.
Should triathletes do brick sessions every week?
One brick session per week is sufficient for most triathletes. The purpose is to rehearse the bike-to-run transition, not to accumulate extra training stress. A 90-minute ride followed by a 20-minute run at race pace teaches your legs to handle the transition without requiring a full race simulation every week.
Is polarised training effective for triathletes?
Yes. Research from Stephen Seiler and others shows that the 80/20 polarised approach — 80% easy, 20% hard — works across all endurance disciplines. For triathletes, this means most cycling sessions should be genuine Zone 2, with 1-2 quality sessions per week targeting threshold or VO2max intensities.
