Coach Rich claims to sit up below 13 mph - seems kinda quick for mortals. Me, I go by % grade (which I display via barometric measure on my Joule), usually anything steeper than 6-7% will have me sitting up. The main reason is comfort - too much sitting up on my TT bike is uncomfortable; it feels better to be down, even if I'm not getting much aero advantage. Since we're not trying to maximize watts on the uphills, unlike road racers, I don;t see an advantage to sitting up as long as I can hit my power target in the aero position.
The answer is their is power savings at ALL speeds. The 13mph number is that above that 90% of power is to overcome frontal resistance. Below this it is less than 90%, but STILL the major factor. Some good papers on where power goes to (air resistance, chain friction, tire resistance, bearings, etc) by James Martin from University of Utah ESS lab. Most recent I saw a webinar from here that showed study data from power data in tops, hoods, drops uphill time trial at <10mph. Convinced me to stay aero at all costs when racing, also train SOME hills this way.</p>
All of these answers (and anything I will say) are in the general neighborhood of right, even if we quibble about 1 mph or 80% vs 90% or whatever.
The really important thing is that the sit-up factor is for slowness due to uphill grade, not for wind in your face. I'll sit up for a break going uphill somewhere in the <12 mph range, in part to give the legs a break and in part because it's a little easier to generate the slightly higher power sitting up... <br /> If the wind is at your back going uphill, then you can afford to sit up at a little higher speed. But if the wind is in your face at all, stay down unless you are just forced to sit up by too steep a grade. It should go without saying that you HAVE to stay down if you are on a flat (or very low grade) and are going slowly because of wind in your face instead of gravity.
Yes, William you are correct. The science can only say what the numbers are, not what is "best" for each person. While you may use more watts in sitting up, it may save your back for later in the run, or allow more O2 intake. Everyone needs to evaluate this for them selves. Just like the lowest position you can get into is not the best for every distance and age.
As Richard notes, going upright provides a good opportunity to stretch the low back - especially nice for us 50+ boomers.
I also find it easier to vary the pelvic angle and engage my glutes over my quads, and vice versa, when in the upright position. I find this a little more challenging in aero, but getting good practice on the trainer during NOS and now GF plans.
I use 12 mph as run of thumb for sitting but William is right to point all the other variables that impact this. when I hit 12 mph I'll use it as a chance to do a body check. Do I need to stretch, drink, eat? I find I can do these things going uphill and it helps me keep my watts in check.
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The answer is their is power savings at ALL speeds. The 13mph number is that above that 90% of power is to overcome frontal resistance. Below this it is less than 90%, but STILL the major factor. Some good papers on where power goes to (air resistance, chain friction, tire resistance, bearings, etc) by James Martin from University of Utah ESS lab. Most recent I saw a webinar from here that showed study data from power data in tops, hoods, drops uphill time trial at <10mph. Convinced me to stay aero at all costs when racing, also train SOME hills this way.</p>
The really important thing is that the sit-up factor is for slowness due to uphill grade, not for wind in your face. I'll sit up for a break going uphill somewhere in the <12 mph range, in part to give the legs a break and in part because it's a little easier to generate the slightly higher power sitting up... <br />
If the wind is at your back going uphill, then you can afford to sit up at a little higher speed. But if the wind is in your face at all, stay down unless you are just forced to sit up by too steep a grade. It should go without saying that you HAVE to stay down if you are on a flat (or very low grade) and are going slowly because of wind in your face instead of gravity.
Yes, William you are correct. The science can only say what the numbers are, not what is "best" for each person. While you may use more watts in sitting up, it may save your back for later in the run, or allow more O2 intake. Everyone needs to evaluate this for them selves. Just like the lowest position you can get into is not the best for every distance and age.
As Richard notes, going upright provides a good opportunity to stretch the low back - especially nice for us 50+ boomers.
I also find it easier to vary the pelvic angle and engage my glutes over my quads, and vice versa, when in the upright position. I find this a little more challenging in aero, but getting good practice on the trainer during NOS and now GF plans.