Aero position effect on power & hr
Since the last 2 months or so has been my first experience training with power, I had a question maybe someone can relate to:
I am noticing that while riding on the trainer, when I get into aero position, my power seems to fall off slightly given the same effort that I was riding with before going into aero position. The same seems to hold true for my HR - it is increasing slightly with same effort going into aero position.
Now this is not something that I noticed while riding/racing my tri bike outdoors last season, but I do not have a power meter for outdoor riding. I should say, I didn't feel a difference riding outdoors with no power meter. Is there generally a direct correlation between the two - loss of power/increased hr when in aero? Thanks!
Comments
My understanding is that the - to use a yoga term - "heart space" is compressed in aero and your lungs aren't able to expand fully as they would when you are upright and your chest is open. Therefore, you're taking in less oxygen, and your heart has to work harder to supply the rest of the body with the oxygen it needs.
There's a brief article here on wind tunnel testing and the metabolic effects of aero that was interesting - with a few good pointers at the end: http://www.bikeradar.com/fitness/article/aero-position-isnt-everything-31165/
This line was especially helpful: "They [the aerodynamicist] will tell you this position is going to give you three seconds per kilometer or 25 watts more power, but according to my data the position could imply a 30- or 35-watts lower output, so the net benefit could be a decrease by about 10 watts."
There's another older (2005) study from the Journal of Exercise Physiology that tested the Effects of Aero Position on Metabolic Economy using two 30' TT's at 70% of Vo2 on two different days (http://www.asep.org/files/Peveler.pdf). Take home point from this article: "There does not appear to be the normal metabolic cost associated with riding in an aero position when examining triathletes who train only in that position. From this study it can be recommended that cyclists and triathletes should train in the position in which they race."
Definitely made me feel better about my lower watts/higher HR in aero!
@Jess - great studies on this! Sometimes the obvious needs to explained like this
@Stefan - my HR is definitely HiGHER in this situation, although it may be me trying to make up for loss of wattage when in aero that is causing the increased HR
Bottom line is I am not as comfortable in aero on the trainer as I am on the pavement. Been tough for me to hold aero more than a few minutes at a clip, especially under extreme conditions (FTP zone). I need to get more aero time I guess and zone 3 is probably best place to log that time. Also, although my tri bike is < 1 year old, I'm considering going for another bike fitting this season. Seems like I can use some tweaking there!
@Brad - If you can't hold aero on the trainer for more than a few minutes at a time, it really sounds like you do need to update your bike fit. I *highly* recommend TTBikeFit.com (see the wiki for our discount information). You should take this time to dial in your bike fit.
I train and test in the aero position for the specificity that Jess mentions above.
So it's not always the fit. In my case it has everything to do with the discomfort involved with not having the bike sway. That little bit of movement means everything to me.
Now think about a trail bike and how the geometry of that fits. You are even a bit HIGHER and the body is slightly a bit further moved forward to allow you to push harder on the cranks that still generate more watts.
As you can see from above all watts are affected by different body positions. The higher you sit over the cranks the more you can MASH the bike to produce higher watts. SO you are working very hard to get that big number
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Yes the number will change when you are in the aero position however you will be more efficient and will not have to work as hard being aero so you will not have to battle the wind as much as someone riding next to you on a road bike.
I have been riding with power for years and I know my pain cave trainer numbers are not my going outside numbers on my road bike nor are those numbers the same getting outside on my tri-bike. Do a TT test on each and you will know for sure where you are at.
I'm similar. I can do 3-4 hours outdoors locked into aero but on the trainer it's a LOT harder...I'll do a 2x20' or 2x15' and can keep aero for the first z4 but need to take one or two 1' "sit up" portions.
As to the HR question, my HR is 2-5 bpm higher at a given power output when sittting up.
Huh...I also have a lot of difficulty holding aero on a trainer but not outside. Glad to see I'm not the only one!
When on the trainer, is it better to train in aero to the degree possible because it conditions one to be able to hold that position, or is it better to train on the bullhorns because it makes it easier to put out more power?
Thoughts either way?
I'm the outlier here. I've been doing all my training in JOS on the trainer in aero. I would recommend a good fit, preferably in person (I did TT bikefit but did an awesome one in person 1/5/13). The fitter taught me the proper position in aero (after he nailed the fit) so I am engaging my core efficiently. When i settle into proper position I can see my watts go up effortlessly. Also, strong core is essential to holding aero so don't forget the ab work!
It depends on when you are in the trainer in the relation to your race. The short answer is to ride the bike / position that allows you put out the highest watts at the lowest mental / motivation cost. However, as you get closer to your race, you need to begin producing watts in a race specific postion, or, if you've been on a road bike, converting those road bike watts to tri bike watts.