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watts/kg - stupid question
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This seems like an obvious question, but I feel like I need clarification!


So I raced IMWA 2 weeks ago. Race was unspectacular. I was expecting to bike a bit better. I rode 5.23 last year with 1 flat and a slow flat going down from 60kms. So who knows how much quicker I could have ridden. FTP was 257w and weight was around 72kg. I wasn't on a program, not biking enough and running lots. This year I was on a program, in hindsight not enough running (calf injury was partially responsible) biking was solid so was expecting 5.05 - 5.10. I rode 5.17 and overbiked. It was hot and windy, the wind shifted 180 so we had a double headwind, but still..... so I was a little perplexed as to why I battled so much, FTP was around 280. I was heavier though, probably close to 75kg, the lack of running didn't help and although I eat well, I do need to get some specific nutritional advice. Maybe too many carbs.

So then the penny dropped, I worked out watts/kg and I was virtually the same. I've never really paid too much attention to watts/kg. It doesn't really get mentioned, just FTP, what power you're going to race at, not weight in relation to that. So is that right, doesn't matter what your bike fitness, FTP is, it's what your watts/kg are? I was too focused on improving my fitness, cognisant I'd put on a few kegs, but not concerned....
Last edited by: zedzded: Dec 12, 19 18:46
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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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w/kg matters most when you're riding uphill (like over 5%). w/cda matters more for flat, rolling, and downhill situations.

Unless you got very unaero, you should have expected to ride an IM course faster with a higher FTP, even if you were 3 kg heavier.

The thing is...you did ride faster...6 minutes faster.

You pointed out a few things.
Last year you had a flat...call it 3 minutes. You also had a slow leak for 60kms...call that 3 minutes. So you might have rode 6 minutes faster the year before.
You said it was hot...you have to reduce your effort some in warmer conditions...especially for someone who isn't <60 kg...I should know. So lets say you had to ride 5 minutes slower (maybe more) to account for that.
You also mentioned a flip in winds, where you expected to have a tailwind, but got a headwind. Not sure how long you experienced this, or how stiff the wind was...but lets do some math.

If the winds flipped even just for 20 miles, and you were expecting to ride at 25 mph avg at a given wattage, but instead could only do 20 due to the headwind, then you're going to be 10 minutes slower for those 20 miles. So in this hypothetical situation, you still rode net 15 minutes faster with a higher FTP and heavier weight.

You say you over biked, but is that because you rode at a higher percentage of FTP even when factoring in the heat? Or did you deem that you over biked because you fell apart on the run...which simply could be due to you running less and having a calf injury compared to last year?
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Re: watts/kg - stupid question [Jason N] [ In reply to ]
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Jason N wrote:
w/kg matters most when you're riding uphill (like over 5%). w/cda matters more for flat, rolling, and downhill situations.

Unless you got very unaero, you should have expected to ride an IM course faster with a higher FTP, even if you were 3 kg heavier.

The thing is...you did ride faster...6 minutes faster.

You pointed out a few things.
Last year you had a flat...call it 3 minutes. You also had a slow leak for 60kms...call that 3 minutes. So you might have rode 6 minutes faster the year before.
You said it was hot...you have to reduce your effort some in warmer conditions...especially for someone who isn't <60 kg...I should know. So lets say you had to ride 5 minutes slower (maybe more) to account for that.
You also mentioned a flip in winds, where you expected to have a tailwind, but got a headwind. Not sure how long you experienced this, or how stiff the wind was...but lets do some math.

If the winds flipped even just for 20 miles, and you were expecting to ride at 25 mph avg at a given wattage, but instead could only do 20 due to the headwind, then you're going to be 10 minutes slower for those 20 miles. So in this hypothetical situation, you still rode net 15 minutes faster with a higher FTP and heavier weight.

You say you over biked, but is that because you rode at a higher percentage of FTP even when factoring in the heat? Or did you deem that you over biked because you fell apart on the run...which simply could be due to you running less and having a calf injury compared to last year?

Normally on that course you will get a decent tailwind, so some respite, there was a brief bit of a tailwind, but mostly cross or headwinds and it was hot. So in short, I overbiked, but I guess it wasn’t that simple. I stuck to my race power of 180w (179), HR was typically high after the swim, it usually comes down over a period of 10, 15kms, but then we had the headwind. I was pushing 220w into the wind, too much, but was relying on that tail wind to balance it up.

Then it started getting warm, HR wasn’t coming down even as my power dropped down to 170. I was wearing a Kask Bambino with visor and felt like my head was in an oven.

I think I was too fixated on getting a certain bike time, and certain overall race time. It’s not like I was hammering it, but that double headwind broke me. I got sick and struggled to get gels down and it was game over. “Run” was 5 hours. A few guys of similar ability were fine on the bike. I guess in hindsight I should have :

- accepted it was a slow day and eased up
- stuck to HR
- different helmet
- lost a few kgs
- I probably need to do a sweat test too. I lose a shitload of sweat when it’s hot.
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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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zedzded wrote:
Jason N wrote:
w/kg matters most when you're riding uphill (like over 5%). w/cda matters more for flat, rolling, and downhill situations.

Unless you got very unaero, you should have expected to ride an IM course faster with a higher FTP, even if you were 3 kg heavier.

The thing is...you did ride faster...6 minutes faster.

You pointed out a few things.
Last year you had a flat...call it 3 minutes. You also had a slow leak for 60kms...call that 3 minutes. So you might have rode 6 minutes faster the year before.
You said it was hot...you have to reduce your effort some in warmer conditions...especially for someone who isn't <60 kg...I should know. So lets say you had to ride 5 minutes slower (maybe more) to account for that.
You also mentioned a flip in winds, where you expected to have a tailwind, but got a headwind. Not sure how long you experienced this, or how stiff the wind was...but lets do some math.

If the winds flipped even just for 20 miles, and you were expecting to ride at 25 mph avg at a given wattage, but instead could only do 20 due to the headwind, then you're going to be 10 minutes slower for those 20 miles. So in this hypothetical situation, you still rode net 15 minutes faster with a higher FTP and heavier weight.

You say you over biked, but is that because you rode at a higher percentage of FTP even when factoring in the heat? Or did you deem that you over biked because you fell apart on the run...which simply could be due to you running less and having a calf injury compared to last year?

Normally on that course you will get a decent tailwind, so some respite, there was a brief bit of a tailwind, but mostly cross or headwinds and it was hot. So in short, I overbiked, but I guess it wasn’t that simple. I stuck to my race power of 180w (179), HR was typically high after the swim, it usually comes down over a period of 10, 15kms, but then we had the headwind. I was pushing 220w into the wind, too much, but was relying on that tail wind to balance it up.

Then it started getting warm, HR wasn’t coming down even as my power dropped down to 170. I was wearing a Kask Bambino with visor and felt like my head was in an oven.

I think I was too fixated on getting a certain bike time, and certain overall race time. It’s not like I was hammering it, but that double headwind broke me. I got sick and struggled to get gels down and it was game over. “Run” was 5 hours. A few guys of similar ability were fine on the bike. I guess in hindsight I should have :

- accepted it was a slow day and eased up
- stuck to HR
- different helmet
- lost a few kgs
- I probably need to do a sweat test too. I lose a shitload of sweat when it’s hot.

What was your normalized power for the entire bike?
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Re: watts/kg - stupid question [MrTri123] [ In reply to ]
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MrTri123 wrote:
zedzded wrote:
Jason N wrote:
w/kg matters most when you're riding uphill (like over 5%). w/cda matters more for flat, rolling, and downhill situations.

Unless you got very unaero, you should have expected to ride an IM course faster with a higher FTP, even if you were 3 kg heavier.

The thing is...you did ride faster...6 minutes faster.

You pointed out a few things.
Last year you had a flat...call it 3 minutes. You also had a slow leak for 60kms...call that 3 minutes. So you might have rode 6 minutes faster the year before.
You said it was hot...you have to reduce your effort some in warmer conditions...especially for someone who isn't <60 kg...I should know. So lets say you had to ride 5 minutes slower (maybe more) to account for that.
You also mentioned a flip in winds, where you expected to have a tailwind, but got a headwind. Not sure how long you experienced this, or how stiff the wind was...but lets do some math.

If the winds flipped even just for 20 miles, and you were expecting to ride at 25 mph avg at a given wattage, but instead could only do 20 due to the headwind, then you're going to be 10 minutes slower for those 20 miles. So in this hypothetical situation, you still rode net 15 minutes faster with a higher FTP and heavier weight.

You say you over biked, but is that because you rode at a higher percentage of FTP even when factoring in the heat? Or did you deem that you over biked because you fell apart on the run...which simply could be due to you running less and having a calf injury compared to last year?


Normally on that course you will get a decent tailwind, so some respite, there was a brief bit of a tailwind, but mostly cross or headwinds and it was hot. So in short, I overbiked, but I guess it wasn’t that simple. I stuck to my race power of 180w (179), HR was typically high after the swim, it usually comes down over a period of 10, 15kms, but then we had the headwind. I was pushing 220w into the wind, too much, but was relying on that tail wind to balance it up.

Then it started getting warm, HR wasn’t coming down even as my power dropped down to 170. I was wearing a Kask Bambino with visor and felt like my head was in an oven.

I think I was too fixated on getting a certain bike time, and certain overall race time. It’s not like I was hammering it, but that double headwind broke me. I got sick and struggled to get gels down and it was game over. “Run” was 5 hours. A few guys of similar ability were fine on the bike. I guess in hindsight I should have :

- accepted it was a slow day and eased up
- stuck to HR
- different helmet
- lost a few kgs
- I probably need to do a sweat test too. I lose a shitload of sweat when it’s hot.


What was your normalized power for the entire bike?

For what it is worth, same race....
First lap on the bike...NP 235 watts, 2:28 split, second lap with the double head wind and heat....NP 208 watts, 2:38 split....(slight mechanical issue meant a slower time through aid stations and two complete stops needed).
I don't really feel like I overbiked the first lap, more that I deliberately backed off the second lap when that heat hit and there was no massive tail wind home.
Still my run was terrible right from early on and was a 4:25 when it should have been an easy sub 4, if not around 3:45, but I am a fair bit heavier than you (88kg) and don't tend to run well when it is so hot like that.
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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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What's per kilos matters because you have the same heart and lungs for all those kilos. The kilos really hurt on a hot day because they insulate your organs from being cooled.

Your kilos always hurt in a triathlon. There is almost no upside to more kilos on a given body....and I am saying this as a person who is 6 kilos over my tri race weight getting back into tri.
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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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I might change the way I feel about watts/kg in the future but for now I will say it should only be used for training to get stronger. You should know a number to hit on races while checking HR for a reality check. You should find that number by figuring out the maximum power you can hold for 5 hours while staying in upper HR zone 2. If 180 watts is that power number then do your 5 hours rides at that number with your 4x20, 5X30, whatever at 200 watts dropping down to 180 for your recoveries. Hill Sprints at 300 watts if you want but drop to that 180 and let your HR drop back into Z2. As you get stronger your HR will become more efficient and 185 will become the number then 190 etc... Forget about holding a watts/kg or FTP numbers during IM. Too many variables, imo.

http://www.sfuelsgolonger.com
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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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zedzded wrote:
This seems like an obvious question, but I feel like I need clarification!


So I raced IMWA 2 weeks ago. Race was unspectacular. I was expecting to bike a bit better. I rode 5.23 last year with 1 flat and a slow flat going down from 60kms. So who knows how much quicker I could have ridden. FTP was 257w and weight was around 72kg. I wasn't on a program, not biking enough and running lots. This year I was on a program, in hindsight not enough running (calf injury was partially responsible) biking was solid so was expecting 5.05 - 5.10. I rode 5.17 and overbiked. It was hot and windy, the wind shifted 180 so we had a double headwind, but still..... so I was a little perplexed as to why I battled so much, FTP was around 280. I was heavier though, probably close to 75kg, the lack of running didn't help and although I eat well, I do need to get some specific nutritional advice. Maybe too many carbs.

So then the penny dropped, I worked out watts/kg and I was virtually the same. I've never really paid too much attention to watts/kg. It doesn't really get mentioned, just FTP, what power you're going to race at, not weight in relation to that. So is that right, doesn't matter what your bike fitness, FTP is, it's what your watts/kg are? I was too focused on improving my fitness, cognisant I'd put on a few kegs, but not concerned....

Name of the game here is watts/CdA. Not watts/kg. I might have the units wrong, but you get the idea.

Also, it's taken me a year of training the TT bike more outdoors to realize that each time I go out you can't effectively say "that was faster than a few months ago". You instead have to have a game plan and execute it perfectly each time. Each time is a new challenge and you have to analyze each challenge on its own.

You may very well have done great for the day. Don't compare it to last year.
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Re: watts/kg - stupid question [ In reply to ]
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Having time expectations, even on a course you've raced before, are tricky. Heat, wind, your weight, etc are the factors that are not apples to apples. Any idea what average HR was over the two rides? That might give you a better indicator on what was going on with you physically.

I've gotten to where I have power expectations for a ride, nothing more (other than maybe a max HR). The time will be what it will be.
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Re: watts/kg - stupid question [Amnesia] [ In reply to ]
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Amnesia wrote:
MrTri123 wrote:
zedzded wrote:
Jason N wrote:
w/kg matters most when you're riding uphill (like over 5%). w/cda matters more for flat, rolling, and downhill situations.

Unless you got very unaero, you should have expected to ride an IM course faster with a higher FTP, even if you were 3 kg heavier.

The thing is...you did ride faster...6 minutes faster.

You pointed out a few things.
Last year you had a flat...call it 3 minutes. You also had a slow leak for 60kms...call that 3 minutes. So you might have rode 6 minutes faster the year before.
You said it was hot...you have to reduce your effort some in warmer conditions...especially for someone who isn't <60 kg...I should know. So lets say you had to ride 5 minutes slower (maybe more) to account for that.
You also mentioned a flip in winds, where you expected to have a tailwind, but got a headwind. Not sure how long you experienced this, or how stiff the wind was...but lets do some math.

If the winds flipped even just for 20 miles, and you were expecting to ride at 25 mph avg at a given wattage, but instead could only do 20 due to the headwind, then you're going to be 10 minutes slower for those 20 miles. So in this hypothetical situation, you still rode net 15 minutes faster with a higher FTP and heavier weight.

You say you over biked, but is that because you rode at a higher percentage of FTP even when factoring in the heat? Or did you deem that you over biked because you fell apart on the run...which simply could be due to you running less and having a calf injury compared to last year?


Normally on that course you will get a decent tailwind, so some respite, there was a brief bit of a tailwind, but mostly cross or headwinds and it was hot. So in short, I overbiked, but I guess it wasn’t that simple. I stuck to my race power of 180w (179), HR was typically high after the swim, it usually comes down over a period of 10, 15kms, but then we had the headwind. I was pushing 220w into the wind, too much, but was relying on that tail wind to balance it up.

Then it started getting warm, HR wasn’t coming down even as my power dropped down to 170. I was wearing a Kask Bambino with visor and felt like my head was in an oven.

I think I was too fixated on getting a certain bike time, and certain overall race time. It’s not like I was hammering it, but that double headwind broke me. I got sick and struggled to get gels down and it was game over. “Run” was 5 hours. A few guys of similar ability were fine on the bike. I guess in hindsight I should have :

- accepted it was a slow day and eased up
- stuck to HR
- different helmet
- lost a few kgs
- I probably need to do a sweat test too. I lose a shitload of sweat when it’s hot.


What was your normalized power for the entire bike?


For what it is worth, same race....
First lap on the bike...NP 235 watts, 2:28 split, second lap with the double head wind and heat....NP 208 watts, 2:38 split....(slight mechanical issue meant a slower time through aid stations and two complete stops needed).
I don't really feel like I overbiked the first lap, more that I deliberately backed off the second lap when that heat hit and there was no massive tail wind home.
Still my run was terrible right from early on and was a 4:25 when it should have been an easy sub 4, if not around 3:45, but I am a fair bit heavier than you (88kg) and don't tend to run well when it is so hot like that.


Yeah it seems like quite a few people had similar races, unintentionally rode too hard. It kind of sounds moronic, overbiking when we are experienced, well trained, we have heart rate monitors and power meters, but like you I felt I didn't overbike the first lap, power was spot on, HR was 10bpm too high, but I attributed that to the headwind and was waiting for the tailwind to bring it back down and that never happened, then it got hotter which I guess just contributed to the high HR. I was sick and done by 160km and was going to DNF as soon as I hit T2. Had to walk/run (not to be confused with run/walk) the first 20km and then the sickness subsided for a bit.

I guess looking back, I needed to factor in the heat more. it was only 32C, but apparently 40+ out in the Tuart Forest and I needed to change my goals. It's hard when you spend months thinking of split times and race times and get all excited, then the race starts, in a very short period of time, you need to quickly change all your goals. It's almost a defeatist attitude in a way. accepting you've lost the game minutes after the ball has been kicked off....
Last edited by: zedzded: Jan 21, 20 17:10
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Re: watts/kg - stupid question [wcb] [ In reply to ]
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wcb wrote:
Having time expectations, even on a course you've raced before, are tricky. Heat, wind, your weight, etc are the factors that are not apples to apples. Any idea what average HR was over the two rides? That might give you a better indicator on what was going on with you physically.

I've gotten to where I have power expectations for a ride, nothing more (other than maybe a max HR). The time will be what it will be.

IMWA 2018 HR was 143, would have been lower, but slow flat contributed. Actually that's how I figured tyre was going down, it felt fine, but I noticed HR started to rise after being stable for hours at 138.

IMWA 2019 HR was 149. Way too high. Aim was high 130s. It's always high post swim and it gradually comes down during the first 60mins of the ride, but then we had a headwind and then it got hot...
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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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So you raced the same course twice at the same W/kg. Second time you blew up and want to know why.


Quote:
It was hot and windy, the wind shifted 180 so we had a double headwind...



That right there explains everything. Time, HR, all of it.


But back to your original question, W/kg probably is a better metric than simply FTP. Here's the chart that makes the rounds once in a while, and it's W/kg based. Enjoy.


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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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So here's the thing. Increasing power when going against the wind in an IM is the wrong response. Air resistance goes up with the square of the relative air speed, for example if you are going 20 MPH into a 10 MPH, the relative air speed is going 30 MPH against you. So if you go 20 MPH in calm air and you try to hold 20 MPH against a 10 MPH head wind, the air resistance would be more than double that of a calm day. You're just not going to get enough bang for all those energy bucks you will be spending -- even if you increase the power less than enough to maintain the same speed. Just ride to your power. (Note that the determination here is different than dealing with hills -- there the bulk of your uphill power is gaining elevation -- you are going slow enough where the air resistance is a relatively minor factor, so adding a little power on the uphills gains you a proportional speed improvement.)

The other thing to keep in mind is that if there is a constant wind and you spend half of your miles going against it and half of your miles with it, for a given steady state wattage your time will be longer than if there were no wind. The Joe Friel chart for IM bike power (see https://www.trainingpeaks.com/...meter-in-an-ironman/) calls for a percentage of FTP that is determined based on how long it will take you to do the bike -- the longer the time, the lower the power you should ride at. I know it is a little bit circular, but it all works. Pick a percentage of FTP. Based on your experience (and the expected wind, elevation gain, and other conditions), approximate your velocity at that power. Compute your projected bike leg time. Then see if the percentage you picked makes sense (on the table) for the projected time -- if not, change your goal power up or down as appropriate and check again.

Anyway, you do that process before the race. If during the race you find that conditions are worse than you expected, then you know at your projected power the bike leg will take you longer and so you need to reduce your power (which will add even a little more time -- but you will have usable legs for the marathon afterwards).
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Re: watts/kg - stupid question [hugoagogo] [ In reply to ]
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hugoagogo wrote:
So here's the thing. Increasing power when going against the wind in an IM is the wrong response. Air resistance goes up with the square of the relative air speed, for example if you are going 20 MPH into a 10 MPH, the relative air speed is going 30 MPH against you. So if you go 20 MPH in calm air and you try to hold 20 MPH against a 10 MPH head wind, the air resistance would be more than double that of a calm day. You're just not going to get enough bang for all those energy bucks you will be spending -- even if you increase the power less than enough to maintain the same speed. Just ride to your power. (Note that the determination here is different than dealing with hills -- there the bulk of your uphill power is gaining elevation -- you are going slow enough where the air resistance is a relatively minor factor, so adding a little power on the uphills gains you a proportional speed improvement.)

The other thing to keep in mind is that if there is a constant wind and you spend half of your miles going against it and half of your miles with it, for a given steady state wattage your time will be longer than if there were no wind. The Joe Friel chart for IM bike power (see https://www.trainingpeaks.com/...meter-in-an-ironman/) calls for a percentage of FTP that is determined based on how long it will take you to do the bike -- the longer the time, the lower the power you should ride at. I know it is a little bit circular, but it all works. Pick a percentage of FTP. Based on your experience (and the expected wind, elevation gain, and other conditions), approximate your velocity at that power. Compute your projected bike leg time. Then see if the percentage you picked makes sense (on the table) for the projected time -- if not, change your goal power up or down as appropriate and check again.

Anyway, you do that process before the race. If during the race you find that conditions are worse than you expected, then you know at your projected power the bike leg will take you longer and so you need to reduce your power (which will add even a little more time -- but you will have usable legs for the marathon afterwards).
I agree you shouldn't try and maintain speed regardless of wind direction. However I disagree you should just stay at steady power. It is worth trading a little extra effort up a hill or into the wind at the expense of a little power on the flats and downhills, or when the wind is more favourable since the losses are greater at steady state than making the trade, so long as you don't overdo it. You can't afford to go so hard you can't recover while adequately. This is actually most important with wind since the longer you spend in a headwind the more work you do. In the case of a hill where there's only so much altitude to gain and the rate of gain doesn't impact the total work that needs to be done. But with wind, longer spent fighting it means more to fight.
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Re: watts/kg - stupid question [Jason N] [ In reply to ]
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Jason N wrote:
w/kg matters most when you're riding uphill (like over 5%). w/cda matters more for flat, rolling, and downhill situations.


This^^^^ is the answer to the OP's question.
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Re: watts/kg - stupid question [Ai_1] [ In reply to ]
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Ai_1 wrote:
I agree you shouldn't try and maintain speed regardless of wind direction. However I disagree you should just stay at steady power. It is worth trading a little extra effort up a hill or into the wind at the expense of a little power on the flats and downhills, or when the wind is more favourable since the losses are greater at steady state than making the trade, so long as you don't overdo it. You can't afford to go so hard you can't recover while adequately. This is actually most important with wind since the longer you spend in a headwind the more work you do. In the case of a hill where there's only so much altitude to gain and the rate of gain doesn't impact the total work that needs to be done. But with wind, longer spent fighting it means more to fight.

OK, I tried to do some numbers to flesh this out. I used this online calculator for bike speed: http://bikecalculator.com/veloUS.html
I just used the default values of that calculator for: rider (150) and bike weight (22), grade (0%), distance (20), temperature (75), elevation (100), and transmission efficiency (95%). I used 170 watts, clincher tires , and aerobar position. I used a 40 mile out and back with a 10 MPH headwind/tailwind.

Result: about 75 minutes out and 43 minutes back (total 117.6 minutes).

Then I increased power to 175 on the out portion and reduced power on the back. To maintain 170 avg power, I had to reduce the back power to 161.5 (because for average you spend more time against than with).

Result: 117.3 minutes (savings of 23 seconds; about a minute at IM distance) so you are right about increasing power -- there is a little savings here.

Then I went further down the rabbit hole and put an NP calculation in my spreadsheet. Now to hold an NP of 170, I had to reduce the back power to 160.4. And again to your point there was still a little savings -- 17 seconds (47 seconds for an IM).

One last iteration: I increased outbound power to 180. To retain 170 NP, return power is reduced to 148.5. Even here, there is still a little savings: 13.2 seconds (37 seconds for an IM).

OK, I lied (that previous run wasn't my last). I bumped it up to 190 out bound. Now to maintain 170 NP, return power is 112. Result: it takes more than 2 minutes longer than 170 steady state (almost 6 minutes longer for an IM).

So where is the break point. If outbound goes to 183 watts, return (for 170 NP) is 140 and it is a couple of seconds slower than steady state 170 for the 40 miles.

BOTTOM LINE: If you do it just right, you can save a small amount of time by slightly increasing your watts against the wind as long as you hit your NP by reducing your power even more in the downwind. But the risk/benefit here is tricky. Steady state is safe. Increasing power has risk of losing a lot more than could have been gained by dosing the headwind power increase just right. My example would probably be the easiest to manage (out and back course with headwind on the way out). If the tailwind is on the way out, it will be harder to know how much you need to reduce your power at the start of your race. Even in my original scenario, it will be hard to have the discipline to reduce power enough on the downwind to hit your NP.

Anyway, that's what the numbers say (at least as I calculated them). But remember, those numbers are worth what you paid for them, so use with care, YMMV, etc.
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Re: watts/kg - stupid question [hugoagogo] [ In reply to ]
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That's where course simulators like Best Bike Split come in. BBS will do all those calculations for you. You choose a target power, and BBS will tell you what power to hold going up shallow/steep climbs, into headwinds, etc. If you have a compatible head unit, it will create a virtual course with power targets which you can "just follow".
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Re: watts/kg - stupid question [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
That's where course simulators like Best Bike Split come in. BBS will do all those calculations for you. You choose a target power, and BBS will tell you what power to hold going up shallow/steep climbs, into headwinds, etc. If you have a compatible head unit, it will create a virtual course with power targets which you can "just follow".

Agreed for when you know conditions in advance and they are projected to remain steady state. The OP indicated that winds shifted 180 during the IM ride. Is there some advanced BBS function where you can input wind changes over the course of the ride? Even if there is, you would need a really accurate hour by hour (or even more granular) forecast and the time to put in the info before the race. The forecast would have to hold over the whole course (e.g., how about Kona where winds blow in different directions at the same time depending on where you are on the the course).

So the question is how do you react when the conditions in the race do not match what you were expecting. I think there is a natural reaction to ramp up power in a headwind. I think that can be dangerous unless well tempered. You have the chance to save a little time but you have the risk to blow up if you get seduced into over correcting against a headwind. On top of that, unless you get a net tailwind, a windier day will be a longer and slower day, so you may indeed need to reduce NP to keep your IF in the proper range.
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Re: watts/kg - stupid question [hugoagogo] [ In reply to ]
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hugoagogo wrote:

Agreed for when you know conditions in advance and they are projected to remain steady state. The OP indicated that winds shifted 180 during the IM ride. Is there some advanced BBS function where you can input wind changes over the course of the ride? Even if there is, you would need a really accurate hour by hour (or even more granular) forecast and the time to put in the info before the race. The forecast would have to hold over the whole course (e.g., how about Kona where winds blow in different directions at the same time depending on where you are on the the course).

So the question is how do you react when the conditions in the race do not match what you were expecting. I think there is a natural reaction to ramp up power in a headwind. I think that can be dangerous unless well tempered. You have the chance to save a little time but you have the risk to blow up if you get seduced into over correcting against a headwind. On top of that, unless you get a net tailwind, a windier day will be a longer and slower day, so you may indeed need to reduce NP to keep your IF in the proper range.

Yes, BBS does have an advanced feature that pulls hour-by-hour forecast wind-vector data.

My point was that you spent time with a VERY BASIC calculator learning that what you "thought" was the optimal strategy wasn't. BBS is much more sophisticated that takes real course elevation profiles, and detailed weather data to do something much more complex than you can do "by hand".

You're right that for the everything to "go according to plan" the forecast must no change significantly. However, BBS (or similar) is also EDUCATIONAL for understanding the appropriate strategies and learning how to react to a change in conditions. It will give you a detailed graph of the entire course, the power profile, the wind profile, and the elevation profile. So, you can see what optimal looks like (as opposed to intuitive). BBS can also print out a power and pace charts for the various conditions, which can give you a template for how to react in real-time if conditions change (stiff headwind/steep hill == XXX watts).

You can play what-if games (like you did above), and see what impact changes in effort has. With that you can develop a deeper understanding of what an optimal response to a set of conditions looks like, instead of what you THINK it looks like. As evidenced above, intuition with these things is often wrong.

I usually start analysing a course in BBS 2 weeks out from a race. I'll do several runs, trying a couple different IF/VI settings until I settle on a strategy based on desired risk, and long range forecast (if its going to be cool, I may take some chances). I'll study the course for major climbs and possible decision points. I do another set of runs a week out, looking for any major changes in the weather mostly. Then, I'll do a final run the day before; and print my power (and pace) charts, and tape them to my extensions.
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Re: watts/kg - stupid question [zedzded] [ In reply to ]
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I have an even dumber question:

Does W/kg include the mass of the bike, or just the mass of the rider?
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Re: watts/kg - stupid question [rosshm] [ In reply to ]
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In general, just the mass of the rider

the world's still turning? >>>>>>> the world's still turning
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Re: watts/kg - stupid question [rosshm] [ In reply to ]
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rosshm wrote:
I have an even dumber question:

Does W/kg include the mass of the bike, or just the mass of the rider?

When discussing physiology/fitness....just the rider.
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Re: watts/kg - stupid question [Jason N] [ In reply to ]
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Jason N wrote:
w/kg matters most when you're riding uphill (like over 5%). w/cda matters more for flat, rolling, and downhill situations.

^ This.

- Jordan

My Strava
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