The WattPlan Podcast · Episode 26 · 9 min
Is the turbo as good as the road?
Next episodes: How long does heat training take for cycling? · What does two weeks off the bike really do? · The menstrual cycle and training: should you plan around your phases?
Read the transcript
James. Hello, and welcome to the WattPlan Podcast. I'm James. Between family life, work, building WattPlan and the very occasional podium, I read a ridiculous amount of sports science, and this week we're heading indoors. Is an hour on the turbo really as good as an hour on the road, and how do you stop it turning into a sweaty slog you dread? Lyra, our AI research voice, is with me, and every study we mention is linked in the show notes.
Lyra. For structured intervals, the trainer is often better than the road, because it holds the power exactly where the session wants it. No junctions, no descents, no tailwind flattering you. For long easy riding it's harder to stick with mentally, so most riders do best with intervals inside and the long ride outside. And what decides how well it goes indoors is usually cooling.
James. Cooling? Not the trainer, not the app, not the telly?
Lyra. Cooling. Outside, the air rushing past carries heat away. Indoors, nothing does unless you bring a fan. So your core temperature climbs, your heart rate drifts up, and the power you can hold drops. It's the most underrated part of riding indoors, and there's a neat study behind that.
James. Go on then. How much power are we talking?
Lyra. It's a 2000 study in the Journal of Science and Medicine in Sport by Tatterson and colleagues. Eleven riders from the Australian national road squad did two thirty-minute time trials in a climate chamber, one at 32 degrees and one at 23, same humidity. In the heat, their power was 6.5 percent lower. [1]
James. From a warm room. That's a lot of watts for not owning a fan.
Lyra. It is, and these were elite men, so if you race, that number is about riders like you. The detail I like is when it happened. For the first ten minutes, power was the same in both rooms. The drop came in the last ten. Skin temperature and sweat rate were higher in the heat, and the authors put the loss down to body temperature, not to running out of fuel.
James. Which explains why I feel great on the first interval and die on the third.
Lyra. Exactly that. Indoors, the opening minutes feel easy because you haven't heated up yet. So ride the first interval as a pacing check, not a test of courage. If it starts to bite early, back the targets off a touch rather than abandoning the session.
James. Hang on, though. Isn't a hot room just free heat training? Surely suffering in the spare room makes me tougher for summer?
Lyra. That study can't tell you, because it wasn't about heat training. It measured performance in the heat on the day. What it does show is that a hot room takes watts off the session you planned. If the point of tonight is threshold work, a hot room means less threshold work. So open a window, point a big fan at your chest, and add a second if you have one.
James. Fine, I'll buy a fan. And the trainer itself, what's it doing in a WattPlan session?
Lyra. The player connects to your smart trainer, power meter and heart rate strap over Bluetooth. In ERG mode the trainer holds the target power and you hold the cadence. A smart trainer measures power itself, so you don't need a separate meter.
James. And when ERG feels like riding through treacle?
Lyra. Shift into the middle of the cassette and keep your cadence steady, and the trainer adjusts around you. If it won't hold a target at all, check the trainer is connected as the Trainer, not only as a power source.
James. But half the people I ride with do their turbo sessions in a virtual world, racing cartoon versions of each other. Do they have to pick?
Lyra. No. WattPlan workouts have a Download file button that saves the session as a workout file the popular virtual riding apps can load, with the same intervals and targets. And if that app uploads to Strava, and Strava's connected to WattPlan, the ride comes back as a virtual ride, with its power, and counts towards your Fitness like any other.
James. So the plan stays the same and only the scenery changes.
Lyra. Exactly. It suits the long easy ride best, because company makes the hours pass. Just don't let the group ride turn into a race on a day your plan asked for easy.
James. What about testing FTP on the trainer? I've heard ERG wrecks it, because the trainer's choosing the number for you.
Lyra. It would, which is why WattPlan's twenty-minute test doesn't. When the twenty minutes start, the trainer lets go and switches to a flat road with no wind, so you set the effort with your gears. Your FTP is 95 percent of the average you hold. And given the heat finding, test in the same room, with the same fans, you'll be training in.
James. And the ramp test?
Lyra. That one does stay in control. It starts at a hundred watts and adds twenty every minute until you can't hold it, and the ride stops itself when you fade. Your FTP is 75 percent of your best minute. Both are in the library, and both are honest, they can raise your FTP as well as lower it.
James. And the boredom? Because that's what actually stops me.
Lyra. Break the session into pieces. Warm-up, three intervals, cool-down feels shorter than one long hour. Music or a programme helps on the easy bits and the recoveries, then turn it off for the hard efforts so you can concentrate. And focus on the interval you're in, not the ones still to come.
James. Okay, fuelling and drinking indoors. Is it any different?
Lyra. You'll sweat more indoors than outdoors at the same effort, because there's no airflow drying you. That's where the second source comes in, the 2016 joint position statement on nutrition and athletic performance in Medicine and Science in Sports and Exercise. Its core message is that well-chosen food and fluid, the type, the amount and the timing, improve both performance and recovery. And for a fully personal plan, it points you to a registered dietitian. [2]
James. That's a bit general. What does it mean on the turbo on a Tuesday?
Lyra. Fair. In practice, plan for five hundred millilitres to a litre of fluid an hour depending on the room, with electrolytes in it. And if a session runs past ninety minutes, fuel it the way you would on the road. The trainer doesn't change what your legs burn, only how much you sweat.
James. And for someone new to all this, without a smart trainer or a power meter? Is it even worth it?
Lyra. If you're new to structured training, yes. You can ride a workout by feel with nothing connected. Each step then tells you how hard it should feel, out of ten and with a talk test, instead of watts. At the end, the player asks how hard it was, and with no power or heart rate, your answer gives the ride its Load. A fan and a towel matter more than the gadgets.
James. And if you train with power already, which sessions belong inside?
Lyra. If you train with power, the ones that need steady, precise watts. Sweet spot, threshold, VO2max, and over-unders, where you swap from just below threshold to just above. Those are hard to ride cleanly on real roads. Keep indoor endurance rides to an hour or ninety minutes, and take the long one outside when you can.
James. Where does the evidence run out?
Lyra. The heat study is eleven elite men, two rides, in a climate chamber. It doesn't tell you how much a fan wins back, or what a cool garage in January does. And nobody has compared, in a proper trial, a winter of indoor intervals against the same work outside. We're reasoning from control and consistency, which is a good reason, but not a measured one.
James. So what do I do this week?
Lyra. Three things. Set up the room first, a window open and a fan on your chest. On your next interval session, ride the first rep as a pacing check, and if it's too much, tap the minus button in the player, which takes every target down five percent. And for one session, drink five hundred millilitres to a litre in the hour, with electrolytes, and see how the last interval feels.
James. Cool room, easy first rep, drink properly. And if I'm testing my FTP, same room, same fans, so the number means something.
Lyra. Indoors, the watts are exact, but the room decides how many you get. Sort the air before you worry about the session.
Lyra. The full article and every study we mentioned are on the WattPlan blog, linked in the show notes. And if you've enjoyed this, follow the WattPlan Podcast wherever you're listening, so you don't miss the next one.
James. And if you want a plan built around the time you've actually got, get WattPlan on the App Store or Google Play. Thanks for listening.
Voices produced with ElevenLabs. James's voice is a clone of his own, Lyra is an AI voice, and James reviews every episode.
Indoor training used to be a last resort. Cyclists would reluctantly bolt their bike onto a turbo trainer when the roads were icy, count down the minutes, and get off as soon as possible. That era is over. Today, some of the most productive training hours happen indoors, and many riders choose the trainer even when they could ride outside.
Why does indoor training work?
The indoor environment removes variables that make outdoor training inconsistent. No traffic lights, no descents, no tailwinds flattering your speed. Every pedal stroke counts toward the prescribed intensity.
Controlled power output. On a trainer, you can hold 245 watts for exactly 20 minutes. Outside, terrain and traffic constantly disrupt your power. For threshold and Sweet Spot intervals, this precision matters. The training stimulus depends on sustained time at the target intensity, and indoor riding delivers that with near-perfect accuracy.
Time efficiency. A focused 60-minute indoor session can deliver as much Load as a 90-minute outdoor ride. There is no coasting, no soft-pedalling through junctions, no 10-minute warm-up ride to reach a quiet road. You clip in and start working.
Weather independence. Consistency underpins almost every training plan that works. Losing two or three sessions per week to rain, wind, or darkness undermines even the best training plan. Indoor training eliminates weather as a factor entirely.
Safety. Intervals that require deep concentration, like VO2max efforts where you are at your physical limit, are safer on a stationary trainer. You can close your eyes on the last rep if you need to. Try that on a B-road.
What equipment do you need for indoor cycling?
Not all setups are equal. Here is what matters and what does not.
Smart Trainers vs Classic Trainers
Smart trainers (direct-drive or wheel-on with power measurement) are the gold standard. They measure power accurately, adjust resistance automatically during structured workouts, and communicate via Bluetooth or ANT+. Direct-drive models like the Wahoo KICKR or Tacx NEO remove the rear wheel entirely, providing a more stable and quieter ride.
Classic trainers (fluid or magnetic resistance, no power measurement) still work if paired with a separate power meter on your bike. You control resistance manually and read power from your crank or pedal meter. This is less convenient but perfectly functional for structured training.
If you are buying one piece of equipment, make it a smart trainer, and choose it carefully. The automatic resistance control transforms indoor training from tedious to engaging.
The Rest of the Setup
- Fan. Non-negotiable. Without wind resistance cooling you, core temperature rises rapidly. A large floor fan pointed at your torso is the single most impactful accessory. Two fans are better.
- Heart rate monitor. Chest straps remain more accurate than optical wrist sensors, especially during high-intensity efforts where sweat and movement cause dropout.
- Mat and towel. Sweat corrodes components. Protect your bike and floor.
- Screen. A tablet, laptop, or TV to display your workout and provide entertainment during longer sessions.
Workouts That Shine Indoors
Certain workout types are dramatically more effective on the trainer than on the road.
Sweet Spot intervals (88-94% FTP). The 2x20 or 3x15 at Sweet Spot demands sustained, uninterrupted power. Indoors, you hold the target wattage precisely. Outdoors, the same session might take twice as long due to terrain and interruptions.
Threshold intervals (95-105% FTP). Efforts at or just above FTP require tight power control. Even small surges above target accumulate fatigue disproportionately. The trainer keeps you honest.
VO2max intervals (106-120% FTP). Short, brutal efforts of 3-5 minutes demand maximum focus. Indoors, you can push to genuine failure without worrying about traffic or road hazards. Recovery intervals can be truly easy, which is hard to achieve on rolling terrain.
Over-under intervals. Alternating between just below and just above threshold practises riding either side of threshold. These require precise power changes that are nearly impossible to execute cleanly outdoors.
Endurance rides. Zone 2 work is viable indoors, though mentally challenging for longer durations. Sessions of 60-90 minutes at low intensity are reasonable. Beyond that, most riders benefit from taking their endurance work outside when possible.
Getting the Most From Indoor Sessions
Pacing
Start conservatively. Indoor efforts often feel easier in the first few minutes because your body temperature has not yet risen. By minute 15, that "easy" Sweet Spot interval can feel like threshold. Let the first interval be a pacing reference before pushing harder in subsequent efforts.
Cooling
This is the most underrated factor in indoor performance. Without adequate cooling, your core temperature rises, heart rate drifts upward, and power output drops. In one study of elite cyclists, 30-minute time trial power was 6.5% lower at 32°C than at 23°C. Open a window, use a fan at maximum, and consider a second fan. If your heart rate runs noticeably higher indoors than outdoors at the same power, heat is the likely cause.
Hydration and Fuelling
You will sweat significantly more indoors than outdoors at the same intensity. Plan for 500-1000ml of fluid per hour depending on conditions. Add electrolytes. For sessions over 90 minutes, consume 30-60g of carbohydrate per hour, just as you would on the road.
Mental Strategies
Indoor training is a mental challenge. Some practical approaches help.
- Break sessions into segments. A 60-minute workout feels shorter as "warm-up, 3 intervals, cooldown" than as a single continuous block.
- Use entertainment strategically. Music, podcasts, or video can help during endurance work and recovery intervals. Turn them off during hard efforts to focus on execution.
- Vary your weekly indoor workouts. Doing the same session repeatedly leads to staleness. Alternate between Sweet Spot, threshold, VO2max, and cadence work.
- Set micro-goals. Focus on completing the current interval, not the entire session. One interval at a time.
Structuring Indoor Training With a Plan
The biggest risk of indoor training is doing random sessions without progression. Riding hard whenever you feel good and easy whenever you do not leads to stagnation.
A structured plan sequences workouts across weeks and months, building load progressively and inserting recovery at the right intervals. Each session has a specific purpose, whether that is building aerobic base, raising threshold, developing top-end power or promoting recovery.
WattPlan generates structured training plans calibrated to your FTP, available hours, and goals. Each workout comes with target power zones, interval durations, and expected Load. You follow the plan day by day, and the system tracks your progression through base, build and peak phases, with a taper when you are training for an event.
Connecting Your Trainer
Modern smart trainers communicate via Bluetooth Low Energy (BLE), allowing training apps to both read your real-time power, heart rate, and cadence data and control trainer resistance automatically. When you start a structured workout, the trainer adjusts resistance to match each interval's target power. You simply pedal.
WattPlan's workout player connects directly to your smart trainer, power meter and heart rate monitor via Bluetooth. As you ride, you see your live power output against the target zone, a running Load total, with Weighted Power in the summary when you finish, and your progress through each interval. When the workout calls for 250 watts, the trainer sets the resistance so that a natural cadence produces exactly that. When recovery arrives, resistance drops and you spin easily.
This closed loop between plan, app, and trainer removes guesswork entirely. You execute the session as designed, save the ride, and your training log updates automatically.
Riding WattPlan sessions in a virtual riding app
Plenty of riders would rather do their intervals in a virtual world, and you don't have to choose. The Download file button on a WattPlan workout saves the session as a workout file the popular virtual riding apps can load as a custom workout, with the same intervals and targets.
When you have finished, the ride can come back on its own. If your virtual riding app uploads to Strava and Strava is connected to WattPlan, the ride arrives as a virtual ride, and WattPlan imports virtual rides with their power, marked as indoor, so the Load counts towards your Fitness like any other session.
A virtual world also suits the part of indoor riding most people find hardest, the long easy ride, because riding with other people makes the time pass. Just keep it easy. A group ride that turns into a race isn't the session your plan asked for.
Making Indoor Training Sustainable
The cyclists who benefit most from indoor training are not the ones who suffer through four-hour sessions on the trainer. They are the ones who consistently complete focused 45-75 minute sessions, three or four times per week, month after month.
Keep sessions short and purposeful. Save your longer rides for the weekend outdoors when possible. Use the trainer for what it does best, which is precise, time-efficient, high-quality interval work. Combined with outdoor endurance riding, this approach suits most riders' weeks better than either alone.
Indoor training is no longer a compromise. Done well, it is an advantage.
Sources
- Effects of heat stress on physiological responses and exercise performance in elite cyclists, Journal of Science and Medicine in Sport
- American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance, Medicine and Science in Sports and Exercise