Hi
New user here… Does the analysis take into account bike weight for w/kg. I have entered my body weight but have multiple bikes and being lightweight 56kg, then an additional 6 to 9.5kg is significant. So does the system use a generic bike weight or only body weight to do calculations from.
If bike weight does it know differences bike to bike?
Are you referring to the power duration curve (PDC)? That will be your body weight only, excluding gear, i.e. whatever your weight was on the day of the effort. If the weight is not filled in, it takes the previous value.
1 Like
Thanks… Not the PDC, I meant any calculation of w/kg. Where does the gear weight come from or is it not considered, or does it use the Strava/Garmin value that is pulled down?
Where are you looking to find the W/Kg?
W/kg calculations never consider equipment weight. Just body weight/ power at ‘FTP’ (or other baseline time period)
1 Like
Strava might use that for cyclists that don’t have a power meter. If you calculate power from speed/grade/windspeed/ frontal surface…, the weight of the gear plays a role.
If you have a power meter on your bike, it doesn’t influence your power curve. You will always put out the same power but you will be slower on a heavier bike. Measured power is measured power.
Yes I get that, that’s not what I was getting at. Specifically my group are all climbers and we want to look at w/kg as well as absolute power, hence we want to know the basis of the calculation. Clearly if I ride my 6kg light climber vs 10kg gravel bike it’s 4kg difference, and on a weight of 56kg that’s 8%. Hence why I want to know if bike weight is factored in, as the total system is you and gear, so it should be to make w/kg relevant?
Yes but that only influences how fast you’re going on a specific bike. Power and HR will look exactly the same if you put in the same effort. The one with the combination of lowest body weight and the lowest bike weight (most expensive?) will be faster if everyone puts out the same power. That is on a sustained climb, because short steep climbs depend way more on VO2max power. So I don’t really understand what you want from this. Why would you want any calculation to take this in account? All that can be said afterwards is that you are a bit slower on a heavier bike (if there’s significant uphill terrain - on a flat ride the difference will be almost non-existant), but you don’t need numbers for that. It’s simple logic and there’s nothing ‘training related’ that you can deduct from it.
1 Like
It’s exactly long hills we are talking. In terms of specific training then yes the effect isn’t important, but if I am comparing the same climb on two bikes it is, as my absolute power won’t change but w/kg will.
You may not have an interest in this metric but we do otherwise I would not be asking
I still don’t understand! Your power is your power and is absolute, regardless of your bike weight.
When you want to compare a climb on two bikes, what is it you want to compare? Times is it? You don’t need w/kg for that. Watts remain absolute. Heavier bike (assuming all other things equal) will result in slower time? Or am I missing something?
I can’t think of a scenario where what you’re asking for is of any use. Doing the same climb on different bikes means you have to do that climb at different times, which means conditions cannot be replicated, which means there are many more variables to factor besides bike weight.
Makes two of us.
w/kg is an athlete specific metric. I’ve never heard of w/kg on specific bike. Just like VO2max is ml O2 / kg body weight / minute.
I’m not opposed to it, if there’s an explanation on what it can tell us. And that’s what I fail to see at this moment. I may be missing something, so please explain.
If you regularly swap bikes and want to plot your w/kg, you no longer can if you take the bike weight in account because you would be comparing apples to pears.
Thanks. We use as a group w/kg as a useful comparison of performance when climbing as where everyone is a different weight then absolute w is no use. Yes the eventual time on a climb will come out but it’s useful for us to see w/kg on say a one hour 1000m elevation climb
I disagree in regard that saying w/kg is the same as VO2 in terms of being specific…vO2 max is a biological parameter which can only be influenced by the body only, whereas w/kg is not. ? You are moving a total system weight up a gradient that your power drives, if the bike weight isn’t considered then you have no idea if your using a 20kg steel bike packing bike vs a 5kg carbon frame? If I put the same power out on a climb I could have a say a value of 3.5 w/kg on a heavy bike and 4kg w/kg on a light bike if the weight isn’t factored in. If bike weight was included then w/kg would be the same.
I hope you can see where I am coming from, it’s not about individual training only, your perhaps thinking of this on that level.
I 100% agree it has no bearing riding on flat as gravity is equal for all weights at that point.
It’s kind of what I thought and this is by no means offensive but your logical thinking isn’t quite correct here.
I will try again to explain that the weight of the bike has absolutely no influence on your w/kg metric.
w/kg is a metric that is specific to you as an athlete. If you put out a max effort and measure the power that you generate, there will be no difference being on a heavy or a light bike. If you measure time, during that same effort, there will be a difference in time because you will go a bit slower on the heavy bike.
I think I know where this confusion comes from. In the beginning years of Power meters, the investment for one was quite high and a lot of people searched other alternatives. That’s where algorithms were developed to deduce/calculate power from speed. You can get a pretty good estimate of power, especially on longer climbs, needed to overcome a certain grade at a certain speed. And in this calculation, the weight of the bike is definitely important. Because power as the result of a certain speed on a certain grade is the power needed to physically take you and your bike up that hill. If you don’t consider the weight of the bike in this case, your personal w/kg will be underestimated by the algorithm. After all you’re not only taking yourself up that hill, but you’re also taking your bike along. And it is the sum of the power needed to take both up that hill that needs to be divided by just your weight to calculate your w/kg.
Damned, this is much harder to explain then I thought. I just hope I did a good job…
Rethink your own saying here below and it should become obvious:
It’s clear that you’re NOT putting the same power if you say 3.5w/kg and 4w/kg. You may need to put out the higher w/kg on a heavier bike to get there in the same time frame. But if 3.5w/kg is your max, you can’t and it will take more time.
2 Likes
like @MedTechCD, I agree with the assessment. Let me share some graphic and such (this is the site / physics math I use for my BreakAway app to model the forces applied to the rider and thus simulating climbing)
I’m sharing 2 pics here. All the same conditions except one is Bike weight = 10kg and another, bike weight = 0kg, 5% Grade
Bike Weight 0kg, at 200w constant power you ride at 15.94kmh
Bike Weight 10kg, at 200w constant power you ride at 14.42kmh
So yes, clearly all things remain equal (same human, same human weight / same w/kg) the lighter bike will get you up faster but w/kg remains the same because its your weight
Thanks, makes sense, kind of!
In my example let’s say I put out Ftp of 280w and my weight is 60kg and a bike 10kg = 280w/70kg total =4w/kg.
Now I ride at same ftp power of 280w that I am capable of on a lighter bike of 5kg 280W/65kg= 4.3w/kg.
My power has stayed the same, but the result in w/kg has gone down. Hence why I am interested in the total system. Yes speed would be slower in #1
I think we are on the same page but coming at it from opposite ends, I am looking at an output in w/kg, whereas your considering an input in W.
w/kg by definition is your power output divided by your weight.
But if you want it to be as “system” weight, then sure you can add your bike weight into the mix.
TLDR, Weight in intervals.icu is your weight, and not system weight.
1 Like
@Brit_In_Oz as the others already said w/kg in the context of training here is by definition the power output in relation to the body weight. This is specifically used to make efforts / athletes more comparable.
Look at it like this, you and a mate cycle up a hill at the same speed and clock in the same time.
Your system weights are the same, so the needed power to achieve that time on that specific incline would be exactly the same.
But the riders were on different bikes one weighed 10kg and the other one 20kg, so their respective body weights must differ by 10kg.
If you compare the measured! power output afterwards it will be the same, but the rider with less body weight and the heavy bike put in a higher effort in relation to his body weight.
This is exactly the information you want to get by using the w/kg metric. If you know the riders weight and the power output you have a comparable indicator of effort disregarding equipment weight and other factors.
Thanks for you reply but I think you have misunderstood my aim. I never said we rode up in the same time, I said we use w/kg as a comparison when climbing. Clearly if we arrived at the same time the w/kg must be the same that would be obvious.
I am enquiring about why the expression of w/kg does not factor in other weights, on an incline your raising a mass through an elevation (which is the physics definition of power) , hence the total system weight is directly relevant, the physics is clear.
If I rule out a colleague and only look at myself on a variety of equipment my power may always be the same irrespective of equipment, but per kilo of the total system will vary with varying equipment. It’s this that my original question is aimed at… Given its the easiest way to compare multiple people ability on a climb it’s very relevant (for us) , just a power number doesn’t tell you anything comparable.
I hope this makes sense, seems like everyone is coming from a different way of thinking.
In order to solve your problem, you would have to have all weight added to the total, i.e. bike, helmet, shoes, bottles, body, clothing, glasses, phone, spares, fuel, etc.
Too many variables.
Perhaps you should consider using the VAMw/Kg, which non-power athletes would use.
1 Like
I guess you understand by now that power meter is measuring :
your torque on your pedals X rpm of your pedals
Your weight will affect slightly your power performance not your bike weight. For this reason watt are dividing by weight of the athlete (w/kg).
You can train on stationary bikes or smart trainers such as Garmin Tacx, Wahoo, smart bike, at your gym or your home using a power meter. The speed and the weight of your bike doesn’t matter at all.
Weight of your bike matters for speeds but this is not a data from the athlete performance itself it is a matter of competition time trial result using a chronometer.
This time result can be translated in speed but doesn’t enter in the calculation of w/kg.
1 Like