Muscle Recruitment of Trainers vs Outdoors

[RyanH]

Since I've spent a good chunk of the year training on Zwift, I've noticed that I can put out more power at a lower heart rate (and RPE) than climbing outdoors. I assume this is due to slightly different muscle recruitment (don't need to balance on a trainer). Has anyone else noticed this and figured out a good way to avoid it?

Outdoor Climb up Latigo


Zwift Race

[JMeinholdt]

One thing I can think of is not so much related to indoors versus outdoors, but more flat versus hill. Riding on an incline puts you in a different position on the bike which is going to lead to different muscle activation. One thing to consider is that if you've spent a lot more time on the trainer recently then the adaptations have been made to benefit that position. Your HR and power numbers reflect that. The muscles used during incline efforts aren't trained nearly as well which will lead to a higher HR and RPE.

[patchsurfer]

I'm interested in this but from a different angle...I've spent a fair bit of time on the trainer this winter. Raced last weekend, found I was pretty strong on the (few, short) hills and on parts of the course where there was a strong headwind, but found the corresponding tailwind part of the course pretty tough going...I can explain some of that by the amount of work I've put into my core / position over the winter, but definitely not all of it. I tend to do most of my workouts in erg mode, which my be apropos of nothing...

[LeDuke]

1) Micro accelerations and decelerations. Trainer can’t quite replicate that.
2) Different muscle recruitment/activation patterns. A trainer can get close by raising the front end.


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[RyanH]

... found the corresponding tailwind part of the course pretty tough going...I can explain some of that by the amount of work I've put into my core / position over the winter, but definitely not all of it. I tend to do most of my workouts in erg mode, which my be apropos of nothing...

I think that's because trainers most closely approximate the effort of climbing since they use brakes (or similar mechanism) which means you recruit more slow twitch than fast. They don't replicate (as far as I'm aware) motor pacing or high speed efforts.

[TobinHatesYou]

I see the exact same thing and it's likely a compound equation

- LeDuke mentioned microaccelerations. I think this is definitely a big deal on climbs, particularly hairpins.
- Environmental control. I perform best around 55F and I am currently training in the garage with the garage doors open. This alone is worth several BPM vs riding at 70F
- Focus on the road, staying upright, riding in straight lines, looking over the shoulder, etc.
- Intermittent coasting, but for brief enough periods where your HR lag means it doesn't really show much recovery vs the instant loss of power.
- Indoors I ride with a lower cadence...at least 5rpm lower at a given intensity, possibly an unconscious adaptation to put more weight on the pedals and less on the saddle.
- I pay better attention to hydration indoors to cope with the excessive sweating.

[RyanH]

Anyone training on rollers that can share comparable efforts with heart rate data? I'm curious if rollers address the myriad of muscles that are needed for stability which I'm guessing could account for the difference in HR.

[Sidato]

Looking at this from another perspective, could it be that cycling outdoors is just more exciting? And that is naturally causing an increased heart rate. The increased risk naturally causing your body to be on edge, compared to feeling relatively safe and relaxed in the trainer.


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[TobinHatesYou]

Looking at this from another perspective, could it be that cycling outdoors is just more exciting? And that is naturally causing an increased heart rate. The increased risk naturally causing your body to be on edge, compared to feeling relatively safe and relaxed in the trainer.

Yes, one of the points I made. It's not one condition causing elevated HR...it's many, including having to look over your shoulder, scan for hazards, etc.

[Djakninn]

I see similar results in my own training, especially with the way things have gone down this year. I'm not sure if it's a problem though when training to power. I like to see my numbers and when outdoor training is consistent i pretty much knew what my HR would be at a given power. So i got a bit disheartened when those values decoupled. What i found out was that once i returned to outdoor riding for a couple of weeks and got a few LSS Z2 HR rides in that things started to align again. I also noticed that the difference in HR made no difference to power performance. More oft times than not i was able to PB my previous power on various climbs during a return to outdoor riding, regardless of what my HR was doing

[Nohands83]

I see the same thing. Heart rate wise, I think it's mainly down to muscle recruitment - you use less upper body / core on the turbo as you're not actually 'riding' your bike. Fewer muscle groups used - less strain on the cardio system.

Power is similarly related to muscle recruitment but more specifically the shape of your pedal stroke. Some people gain power indoors some people the opposite. Turbo trainers lack the same inertia you have on the road (some are significantly better i.e. Neo), some people's pedal strokes react / work better than others to this difference in inertia.

FYI lots of lengthy (and very informative) discussions about this subject on the UK time trialing forum, as this power difference is even more pronounced in TT position.

[JMeinholdt]

I see the same thing. Heart rate wise, I think it's mainly down to muscle recruitment - you use less upper body / core on the turbo as you're not actually 'riding' your bike. Fewer muscle groups used - less strain on the cardio system.

While muscle recruitment is one of the factors, whether it's the main one is up for debate.

Your autonomic nervous system can (and does) jack your HR over so many factors that you may not even realize are happening. For example, it's entirely possible that the second you turn onto a busier road, you may not think much about it, but your ANS is subconsciously kicking your awareness into a higher gear which would put your HR a few beats higher. It's not much, but it adds up.

I could be riding along outdoors at 130bpm and if I see a dog out of the corner of my eye running towards me, my HR will ramp up 20-30bpm easy in just a few seconds.

You absolutely cannot discount the effect your ANS has on your HR.

[Nohands83]

I see the same thing. Heart rate wise, I think it's mainly down to muscle recruitment - you use less upper body / core on the turbo as you're not actually 'riding' your bike. Fewer muscle groups used - less strain on the cardio system.

While muscle recruitment is one of the factors, whether it's the main one is up for debate.

Your autonomic nervous system can (and does) jack your HR over so many factors that you may not even realize are happening. For example, it's entirely possible that the second you turn onto a busier road, you may not think much about it, but your ANS is subconsciously kicking your awareness into a higher gear which would put your HR a few beats higher. It's not much, but it adds up.

I could be riding along outdoors at 130bpm and if I see a dog out of the corner of my eye running towards me, my HR will ramp up 20-30bpm easy in just a few seconds.

You absolutely cannot discount the effect your ANS has on your HR.

That's a really interesting point, something I hadn't considered. There's definitely not as much stimulus on the turbo!

[LouisN]

I noticed that when going down a steep hill outside, my heart rate goes down dramatically.
I always though it was a brain response to help concentrate on potential danger.
I never noticed a dramatic HR drop when doing a downhill segment on Zwift though .

Louis