Yes

Same here

It's very common.

Also, if your indoor setup could be improved, that could help your indoor power. I have no idea what it is in your case. I call a 100 watt circulator-type fan the bare minimum, and no heating allowed in the room.

Also it may depend on how much you train indoors.

In my case, there is little difference in power I can hold for a given time, or power at a particular heart rate or RPE. Outdoor feels easy at first, and then gets harder as the effort starts to bite. Indoors feels more or less equally hard throughout the workout.

---

"FTP is a bit 2015, don't you think?" - Gustav Iden

You generally have way more cooling outdoors. Even riding at 35 kph at 35C celsius on roughly a 37C body you are still cooling. Lots of people don't enjoy living where it is cold, but its a nice advantage training for a hot race in a cold environment. You can do all the high quality training in the cold and you can just do some acclimatization workouts in the heat indoors and some final heat training when you get to the heat.

There is a reason why competition pools are cool. That is what you want to put our lots of watts in any sport (as long as it is not too cold).

In terms of staying aero indoors you don't have a 30-45kph headwind retarding force holding you back in your saddle from putting too much pressure on the nose of your saddle and bars. So you feel better sitting up with your arms pushing your back because tthere is no force of air pushing you backwards from falling forward. For the slightly technical people around here, draw a free body diagram, and on the open road you have mechanical force from back wheel moving bike forward, you have retarding force from air pushing you back, you have gravity pushing you down into your saddle (unlike an aircraft we don't have lift pulling us upwards :-) ). On the trainer you lose the wind drag force pushing against body.

Yeah, not sure this holds any water. At least not for me. I'm not sliding forward and if I am putting any good effort into the pedals that is enough counteracting force to relieve any "pressure" on the saddle. Not to mention my trips to the tunnel have likely been the most uncomfortable time I've ever spent aero and that's with a 50kph headwind. ;-)


To the OP:

In my setup the bike tends to be pretty stationary indoors vs outdoors where it moves around a lot. Also, outdoors I will be out of aero a heck of a lot more than indoors or at least more often. I normally will stand up for 30s every 10 minutes indoors as a preventative measure. If I pay attention to my time in saddle while riding outdoors I rarely make it ten minutes before I have to sit-up for a light, stopsign, hill, etc.

I guess it should also be said that riding outdoors I find it more difficult, or maybe I should say more taxing, to hold aero as I am constantly peaking and or holding my head up, all this with a helmet on no less. Indoors no helmet and no real need to be holding my head up or peaking makes holding aero easier for me. YMMV

I would say the biggest thing in comfort is the stationary/fixed bike indoors vs outdoors. Next would be cooling, but if you're not a huge powerhouse most good fans should be able to mitigate that. I used to run a 10K CFM fan, but it led to some hearing loss and it's not really needed even when doing 6x5x1s at ~300watts. I currently run a LASKO which works well, but I don't do efforts over FTP anymore on the Time Trial bike (which is what I mainly train on).

---

My YouTubes

Hey, you're not exempt from physics any more than the rest of us. We all experience the same force from wind pushing us back against our saddle outdoors. You can deny physics if you want, and you can say its negligible if you want (which is fine), but the math says there is a force from the air that pushes us back. Most people ignore this indoors and try to come up with all kinds of reasons why it feels different, but this is a reasonably substantial contributor to the difference.

I do agree that while riding hard enough indoors the force on the pedals can substantially relieve any pressure from not having wind to hold you back and up.

I personally think it is better to ride indoors on a road bike with a slack position with high bar placement (so more weight is on the butt) and train aero with clip ons, such that the hip angle is same as outdoors and pad positions are the same, but you're just rotated backwards and have gravity working for you since you don't have wind working for you. Then just get outdoors on your real aero position with the same hip angle, but now rotated forward, but you have wind holding you up even though you have more gravity vector pulling you forward.

Nobody is denying physics.....that's a bit over the top to suggest that I am. What I said is that I am not sliding forward when in my position; therefore, I need no retarding force to support my position. Even if I was sliding forward, the same force that you suggest makes things more comfortable when I sit up (me pushing myself back with my arms) is still in play on the trainer when aero as my front contact points are still my arms. If one needs significant airflow to support their position I would argue they have issues with their fit.

ETA: Maybe I am not understanding your position. Are you saying it feels different to push against the air, i.e. a resistive force that helps one put out more power? e.g. power climbing a hill vs power on the flats? Or are you saying you are more comfortable outdoors because that forces props up your position?

---

My YouTubes

I would check out this podcast with Kevin Poultin, who worked at Zwift and is currently developing a new online indoor training platform. He talks about your exact question and how indoor training can compliment outdoor riding throughout the season.

https://scientifictriathlon.com/tts261/

---

80/20 Endurance Ambassador

It may also relate to your trainer. Trainers with no fly wheel are a lot different than riding on the road -- with no forward momentum and no fly wheel, the resistance from the trainer slows your pedal stroke a lot more through your dead spots. This impacts some people (like me) more than others. It made a big difference for me when I bought a Kickr.

Thank you, I’ll check it out.

LAI - I am with you on this one. Not buying it.

---

Mike Sparks


I have competed well, I have finished the race, I have kept the faith.

Yeah, I was thinking that may be a factor. That’s kind of why I mentioned that I don’t have a smart trainer, just an old basic trainer. It feels like more resistance than riding on the road.

Yes to all. I came off a dumb trainer in July and I can relate. My FTP was 15w lower indoors versus outdoors. Thankfully, we race outdoors.

The importance of a good fan situation cannot be overstated. I have three on me at all times.

For me staying aero was a combination of a few factors. If you are working off your outdoor FTP you will fatigue. If you don't have enough fans you will overheat and if you are not moving around every so often, it becomes uncomfortable to be in the same position for long periods of time. Even when you are aero outside, there are little climbs and descents, turns and what not. These things allow you to redistribute your weight and shift the engagement of postural muscles.

While switching to a smart trainer helped with the FTP gap, upgrading the fans was the biggest improvement I made. The next biggest was standing up for 5-10 seconds at the beginning of each interval to reposition myself.

Good luck.

Let me simplfy it. All those molecules of air that you push out of your way outside have the affect of pushing your backwards into your saddle. Indoors you are not moving air you are just moving a trainer flywheel. In a TT position you are rotated forward around the bottom bracket with your weight falling forward a bit. Outdoors that falling foward force which is a percentage of your body weight depending on how forward you ride (I can get intro trigonometry to explain it, but we don't need to) is held up by a combination of your force on the pedals, weight on front of saddle, force on the aero cups and retarding force of the wind. Indoors you lose the retarding force of the wind, so it has to be made up be weight on cups and pedals and front of saddle.

The retarding force of the wind is not zero outdoors. You loose all of that on the trainer.

You don't need to buy it, and you may feel its negligible for you, but it is one of the differences why the same bike feels so different indoors for some. The other delta is side to side motion.

I was not answering the question about generating power with the angle of retarding force of wind, that answer I gave with the cooling capacity of wind (that's a thermodynamics + fluid dynamics discussion + physiology/adaptation discussion)

. It is partially why cruiser bikes are built way laid back with all the weight on the back wheel.

I believe Dev is suggesting the latter of your edit. While power is power, the physical effects on a rider differ significantly indoors and outdoors, which impacts perceived comfort or exertion.

I believe Dev has also noted in the past that a saddle tends to feel more comfortable riding at higher power, since it will reduce the downward pressure of the rider on the saddle.

I can’t speak to the magnitude of these impacts myself, but the different forces at play are fairly straightforward. My guess is that the static position indoors (e.g. lack of shifting weight side to side and front and back) is a more significant factor in general rider discomfort compared to outdoors, rather than the backward force of the wind on the rider.

I thought he was, but was leaving open the possibility that I was not catching what he was trying to put down.


That's my take on things, too.

---

My YouTubes

Your indoor verses outdoor power will be very close when you fully compensate for cooling and airflow.

Also, your road bike verses tri bike (threshold and lower) power will be very close when you fully compensate for hip and thigh-torso angles, including addressing crank length.

Depends on the duration. Longer duration efforts you may definitely see a change depending on your available cooling. But for shorter efforts, it's unlikely. The one area where you almost certainly will see a difference is for pure anaerobic efforts, because sprinting indoors is just more difficult; you can't move the bike underneath you. Sprinting, 10%+ is not uncommon indoors vs outdoors.

Kevin Poulton used to estimate 5-7% lower indoors with a *typical* cooling setup @ threshold. The more cooling you have, the more likely that is to diminish. But for anything longer than 10min, I doubt you'll see parity. 3-5min, I would say parity can and should be expected.

Aerobars are very challenging to ride indoors though. Even accounting for "proper" positioning, the lower inertia of the indoor environment is more challenging to the TT pedal stroke in my experience. Indoor vs outdoor road bike power is only about 3% for me. But indoor vs outdoor TT bike power is quite a bit more than that. A heavier flywheel can help a lot with this. Jens (of this forum) made a 50lb flywheel for his computrainer back in the day that helped a lot with evening out his power indoors vs outdoors.

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

I also notice I ride faster with the sun behind me. I figure it's due to the solar sail effect.

Peak power yes, outside is higher. Holding power for a duration, no, inside is easier. I don't have to worry about someone hitting me, dogs, wind, or what ever. Staying in aero is also easier inside but I have to be disciplined.

How do you define easier? Mental or physical. Physical is should be a wash outside or in. Aero is aero regardless. Mentally I can see the issue staying in aero inside. With no distractions you're brain can wonder and the next thing you know your sitting up.

When I go from indoor to outdoor season it initially find it difficult to hit my indoor power numbers outdoors.

When I go from outdoor to indoor season it initially find it difficult to hit my outdoor power numbers indoors.

---

#######
My Blog

To get an idea of the force of the wind pushing you back; here's a little back of the envelope math:

If you are pushing 200W (flat road), and going a constant speed then there must be 200W of total resistance.

Figure 80% of that is air resistance (20% is frictional losses in the drivetrain and tires). Figure that 75% of the air resistance is the rider, 25% is the bike.

So: 200W*0.8*0.75= 120W is the power of the wind pushing you back.
(you can assume a speed at this power [ex. 32kph] and compute the force: I'm getting 13.5N -> 30.35lbs)


Personally, I find that a 3cm riser (an old book) under the front wheel significantly increases my comfort riding indoors. It may be that the slight incline helps simulate the rearward pressure we get from air resistance outdoors.

---

ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

Is my math wrong or did you miss a decimal place?

13.5N = 3.03 lbs?

Also, out of curiosity what surface area did you assume when calculating force from wind speed? (yes, I am bored ;) )

Yeah, should be 3lbs. Thx for the correction.

No surface area calc (this is just back-of-envelope). Used the rule-of-thumb percentages: 80% of drag is fluid resistance and the rider is 75% of that. Also assumed that 200W resulted in a speed of 32kph (~20mph). Obviously this depends on a lot of factors, but is probably in the range for an average male riding on the hoods.

---

ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)