Ironman Training: Indoor cycling vs outdoor cycling, which is better?

The longest portion of any Ironman race (or triathlon for that matter) takes place on the bike.

In some cases, (including for me when I completed Ironman Maryland last September) it’s more than half the total race time.

The same can be said for time required when going through an Ironman training plan. Most of your time spent, will be in the saddle.

The challenge here is this: the race takes place outside, but it’s simply impossible for the average working person to get ALL their bike training done outside. In fact, it’s difficult to even get a majority of it done out there.

This results in a lot of indoor trainer miles, and a lot of questioning of “does the indoor trainer do a good enough job of preparing me for the race?”, “Will I be at a disadvantage because only a small portion of my training will be done outside?”, etc.

If used correctly, the indoor trainer can actually be a more effective method of training. This, and the requirement of at least getting outside a little bit, is what we’ll be discussing today.

Skill Development

Which training method wins in regard to developing on-road skill (turning, accelerating, climbing, etc.).

Indoor trainer

The indoor trainer is a great way to practice your pedaling cadence and gear changes. Learning to keep a 90+ RPM cadence at various different levels of resistance is a fantastic way to do HIIT (high intensity interval training) style workouts, and work your quads, hipflexors and glutes.

That said, since you’re never turning, braking, climbing, or descending, it does next to nothing for skill development.

Outdoor cycling

Riding outdoors, particularly on a road or trail with a lot of hills and descents, makes it difficult to practice maintaining a high cadence since you’re constantly coasting, climbing, etc.

That said, this is where you truly develop your comfort on the road, dealing with the elements. Learning to climb while maintaining a steady heart rate, learning how to descend in control without riding your brakes, turning, dealing with wind gusts, etc.

Winner: Outdoor cycling

Fitness & endurance

Which training method wins in regard to developing cardiovascular fitness and muscular endurance?

Indoor trainer

If we’re talking about reps, the trainer is a clear winner in this category. Because you’re never coasting, there’s no drafting or slight downhills, you’re constantly battling the resistance provided by your indoor trainer. That constant resistance, coupled with high RPM interval cycling, creates an environment where you may do the ‘work’ (i.e. number of resisted pedal strokes) of a 2 hour outdoor ride, in 45-60 minutes indoors.

Your other benefit of cycling indoors is that you’re in full control. You can create workouts such as the following:

  • 1 hour ride at 90+RPM, broken into the following:
    • 12 intervals of:
      • 3.5 minutes easy
      • 1.5 minutes difficult

Such a workout allows you to pedal constantly for 1 hour (something that will almost never happen outside) at difficulty you can control, and over time, increase to increase your endurance.

Outdoor cycling

When cycling outdoors it can be difficult to get your cadence up to 90+ RPM, particularly if you’re on a trail with many people, or a windy road. That, however, isn’t what outdoor training should be used for.

When you only have a few opportunities to train outdoors, you should try to expose yourself to as much of the following as possible:

  • Long rides – Get comfortable in the saddle, with the wind, and ebbs and flows of the terrain (oh, and learn how to change a tire!)
  • Wind – Gusts aren’t fun to cycle into, but come race day, knowing how to stay in control if it ends up being windy on the course, will assist in keeping you calm and collected throughout your 112 miles!
  • Hills – This is the one nobody wants to do, but it’s arguably the most crucial. Hills are something you can never practice indoors. Get out of the saddle, learn how to gear appropriately for long, grueling climbs, and learn how to do so with a controlled heart rate. Your race day self will thank you.

Winner: Tie (for separate reasons). Indoor cycling wins for HIIT training, and cadence training. Outdoor cycling wins for hill endurance and overall comfort as it translates to race day.

NOTE: Getting comfortable on the bike outdoors doesn’t take long. Maybe 5-10 nice rides outside over the course of a year will do it. Just try to get more outdoor rides as you get closer to race day!

So who wins the indoor cycling vs outdoor cycling battle?

No winner and loser here, just facts.

Cycling indoors when training for an Ironman is more convenient. It’s devoid of weather, traffic, and other elements 100% out of your control.

It should serve as a no-excuses method to get your training in when it’s cold, raining, or dark. It should also be primarily used for HIIT training, and gaining comfort pedaling with constant chain tension at a 90+RPM speed.

Cycling outdoors when training is less convenient, but often more fun. You can explore new roads, trails, and otherwise just enjoy the sights and sounds around you. Finding hills and windy flats help take your outdoor training to the next level, forcing you to learn to be comfortable in uncomfortable situations.

That way, race day is a piece of cake!