Pacing an Ironman Bike – Pete Alfino

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The Ironman bike is arguably the most important of the three legs of the Ironman race.  Pace incorrectly and your run will suffer.  Hopefully, you have spent a lot of time in training dialing in your nutrition and developing a pacing strategy you will use on race day.   The goal of your bike leg is to give yourself the best opportunity to run well off the bike, NOT to ride as hard as you can and hang on for the run.

Let’s look at a few of the key areas to ensuring a successful Ironman bike leg.

  • Don’t spike your heart rate too early. Even for those riding a power meter, don’t ignore your heart rate, especially at the beginning of the bike leg.   Coming out of the water and moving quickly through transition will cause your heart rate to spike.  It is important that during the first portion of the race (first 5 miles) your goal is to get your heart rate into zone two.  Spiking your heart rate too early will cause your blood to be diverted to other parts of your body and will impact your digestive system.  I suspect most GI issues in a race come from too high of a heart rate early in the race.
  • Heart Rate Monitor: If you are using a heart rate monitor stay in zone 2. It is that simple.  There may be times where you slip into zone 3 because of a hill but your goal is to not stray too far from your targeted zones.  This requires patience and trusting your numbers.  Using HR with Perceived Exertion is a good combination but you must establish parameters to both and trust them on race day.
  • Manage your breathing. This will go hand in hand with heart rate but is something to you should pay attention to during the race. If you hear yourself breathing you are going too hard.
  • Pace yourself: Ease to say, hard to implement for most.  For those of you riding a power meter. Your Variability Index will help you with this (Ironman goal is under 1.05).  The VI tells you how smoothly you paced your effort.  For those with a heart rate monitor or riding with Perceived Exertion this takes a little more work.
    • Heart Rate/PE athletes: When you come to a hill SMOOTHLY transition your effort at the base of the hill. This will require you to anticipate the grade change and make the appropriate shift to allow you to not make dramatic effort changes. Done properly and your cadence changes without having to put in big efforts OR make a shift half way up the hill to struggle to the top.  Resist the urge to hammer or chase anyone up the hill. Focus on pedaling in circles, staying light on your bars, engaging your core muscles, not arching your back, but keeping your pelvis in alignment and SMOOTHLY progressing up the hill
    • Power Meter: You Intensity Factor (I/F) should ride between .69 and .73 of your FTP. For Hills there are different formulas out there but the one I like the best is if the climb is over 3 minutes long target 105% of your wattage goal.  Shorter than 3 minutes,  you should be at 110% of your wattage goal.
  • Avoid surges throughout the day. This means your back half of your ride is the same as your first half.  This is a skill you develop in training. It requires patience, letting go of your ego and knowing and studying your numbers.  Think of fuel efficiency in a car.  Would you get good gas mileage if you punched the accelerated and then slowed down all the way to work or if you drove the same even speed?
    • KEY POINT you must understand: When fast twitch muscle fibers are used, more muscle glycogen are recruited than when slow-twitch fibers are recruited.  Your muscle glycogen usage will be greatest you fluctuate power on the bike from hard efforts to slow efforts.
  • Mentally stay in the game: Let’s face it, 112 miles is a long ways to stay focused.  Recognize when you have lost focus and have a mantra which brings you back to center.  Break the race into smaller segments miles 1-20, 20-40 etc and have a pre race goal for each segment.

A well paced Ironman bike leg sets you up to optimize your Ironman run.  Of course your nutrition must be spot on but that is another topic.  Pace yourself throughout the day, keep good mental focus and form and your chances for a successful Ironman bike are enhanced.


Peter S. Alfino is the owner of Mile High Multisport, LLC. He has coached athletes of all ages and abilities to over 200 Ironman finishers. He is a four time Ironman finisher and is passionate about helping others achieve their Ironman dreams. Learn more about MHM and the coaching staff at


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Pete Alfino is a level II USAT certified coach and the owner of Mile High Multisport. An accomplished triathlete who has completed 4 Ironman races, he has successfully coached triathletes of all ages and abilities from sprint to Ironman races. You may contact pete at to learn more about the triathlon coaching services he provides via Mile high Multisport.