Maintaining form continuosly



This is quoted from the message board:


How do we measure power on a Hill CLimb site
posted by Andy Steven on the 26/03/2003

hill climbs



details:
A lot of people ask this question, so I thought I would explain it here.
The formula we use for calculating power is pretty easy:
0.1315 * (climb_distance/time)^3 + 9.81*(time_rider_kg + time_bike_kg)*ascent/time
so basically it is potential energy plus a factor of speed due to wind resistance etc.
The formula is very accurate on a steady climb with no flat spots on a wind free day, provided the ascent is known accurately.
for example a 70kg rider with a 10 kg bike riding at 20 km hour up a total ascent of 300m, distance is 5 km, in 15 minutes(15*60 sec)
Power= 0.1315 * (5000/900)^3 + 9.81*(80)*300/900
Power= 22W from wind + 261 W from potential energy
So as you can see, when climbing wind resistance doesn't count much, so if the ride has no flat sections (faster speed)and is a steady climb at 20km/hr or less the accuracy will be with in 5%, provided the ascent and weights are correct.
 
GearGrinder wrote:
so rick what is a power to weight ratio that most pro climbers have. Just want to see how far i have to improve to be a good climber . Im now at 3.7w/kg for a 4.8k climb at 6.5%. The cycle2max site says thats 238 watts. Do you think that the formula they use would be based on the fact the roads are smooth? this climbs surface is roughish bitumen. heres a link to the page with the climb info http://www.cycle2max.com/c2m/climbs...256D1700243592?
hrm file at botom. Also my average hr as 185 and my max is 206. Is my threshold pretty much as high as it will get? is it good? If its as high as it gets how will i improve?



At 3.7 W/kg on that climb you should be travelling at around shade under 16 km/hr. Using a figure of 70kg for rider and 10 kg for the bike i get a power output of ~ 259 W.

Pro riders are going to climb at ~ 6 W/kg for extended periods of time.

As regards 'threshold' (technically, threshold is way below what you TT or climb at), HR has little bearing on matters. What's important is the average power output that you can sustain, either relative to your MAP (see, http://www.abcc.freeserve.co.uk/powertrain1.html), realtive to your CdA or mass or just as an absolute figure.

Ric
 
But LT is still correlated with performance in TT's! It is an easy measure to make and a good basis for training advice!
 
At 3.7 W/kg on that climb you should be travelling at around shade under 16 km/hr. Using a figure of 70kg for rider and 10 kg for the bike i get a power output of ~ 259 W.

Pro riders are going to climb at ~ 6 W/kg for extended periods of time.

As regards 'threshold' (technically, threshold is way below what you TT or climb at), HR has little bearing on matters. What's important is the average power output that you can sustain, either relative to your MAP (see, http://www.abcc.freeserve.co.uk/powertrain1.html), realtive to your CdA or mass or just as an absolute figure.

Ric

i was going 17.5 kph up that climb and my weight is 64kg with a 8.3 kg bike. add 700g for water etc
 
Sorry, Ric, short on time. Just saying that although LT is below time trial speed as you have stated it is still very useful to the physiologist and cyclist; because it is correlated with TT time and it is relativly easy to measure (when compared to MLSS, etc.).
 
Thats cool Ric.

I'm going to start some reading on power cranks, do you advocate that you use a HR (for more physiological data) as well as power (a measure of output)?

Perhaps I should start a new thread with this one?
 
When i first started using a power meter, way back in 95/96 i was definitely using both HR and power with probably more emphasis on HR (simply because power didn't mean much to me at that point).

Thereafter, and once i started to understand power i pretty much dumped HR and never looked at it again for several years. It doesn't really say much.

In case anyone see's me out training, i do now use a HR strap, but this is simply being used as a) fun to see the numbers occasionally, b) seeing if my HRmax has dropped at all

actually, it also 'annoys' me when i look at my download and see the flat line (0 b/min), and it takes us the same amount of memory whether i include HR or not!

Basically, if you can drive up the power to what ever level you were wanting to train at, your HR will respond accordingly. it's always slightly different due to so many factors which i'm sure you know (e.g., stress, caffeine, temp, etc) that i don't feel it gives any good info.

Dunno whether you should have started another thread though. Drift is always good!

Ric
 
It looks like my only choice is to experiance training with power! I thought that the fact that HR would vary so much relative to Power would give good feedback, if only to make you/the coach question what was causing the changes in HR (i.e. fatigue or heat).

Perhaps simple again, but I have not used power to train with. On some days it can be difficult to elevate HR, once I have determined why I will either head home or continue training. Using power cranks, do you get a similar response (i.e. hard to raise therefore question whether or not to continue?)?
 
The questions that HR causes due to it's variance are generally easy to spot with RPE. You'll just sort of feel good, bad, whatever when you try to ride at a specific power, or can't make that power.

There's definitely days where due to various external factors (e.g., poor nutrition, lack of recovery, stress, etc) you can't raise power to the desired level. under those circumstances, it's *sometimes* useful to change the session on the fly (e.g., going from a hard TT efforts down to endurance), but more often that not i find the best option is to just bag the session.

On some days i can find that my HR is somewhat different to normal (e.g., depressed due to heavy fatigue), depending on what i'm training (e.g., i do blocks of ~ 10 - 20 days with no rest days) i'll either continue or just stop.

One thing to bear in mind when riding outdoors (or on a velodrome) with a power meter is that instantaneous readings can be very stochastic.

Ric
 
How do you prepare the data on the ride and at home, average or instantaneous?

What time for average is most useful?
 
2Lap, i'm not entirely sure what you mean? might just be a result of me getting in from training though :rolleyes:

what i do, both my myself and the people that i coach, is set up zones for training prescription - much like you would with HR - there's a link on the other thread with how i use the zones (the HR is just for comparison). i then set zones for various conditions (just as you would for HR), e.g., zone 2 flat and 4+ on hills on endurance sessions.

don't know if that explains it...

right, off now for 1.5 g CHO per kg BM to aid recovery!

ric
 
Thanks Ric, not quite what I mean't. I'll explain further. Given that the instantanious power output will vary and perhaps make no sense at all as an aid either through the ride or during analysis at home, how do you average the data best for training? 1 second, 10 seconds 1 minute?

A similar problem occurs using online gas analysis whereby breath by breath data can be miss leading. Analysis of 10 breaths, 10 seconds, etc. can prove more useful.
 
ahh right, i see. basically, with either the SRM or the PowerTap, the data is smoothed when presented on screen -- although with both systems you can view the unsmoothed data or look at it in e.g., excel.

the instantaneous power will vary, but within limits (e.g., as you accelerate out of a corner you might hit ~ 700 W), however, due to the way the data is smoothed on screen you don't have to see every single peak and trough.

if anyone knows how to insert graphics, i can show you either srm or pt on-screen data.

when i analyse the data there's various factors i'm looking at including the mean power, the modal power, the distrubition, and just looking at specific sections (e.g., uphill and ignore downhills depending on the situation).

ric
 
Thanks Ric, I have some copies of SRM traces from all different types of races. The images might be interesting with others though.

My problem is that although I understand training with power in theory, I lack practical experiance and those tips that are developed over time. Its good to have your brain to pick!!!

Perhaps we could get a collection of traces posted onto the power forum? I still have to post my biopsy pictures!
 
if someone can tell me how and where to post pics to the web i'd be mucho obliged. although i have a website, my webmaster does everything there -- and i believe the images need to be posted somewhere first, and we just point to them from this forum? Steve, is that right?

ric
 
I've been riding with a powertap for just under a year now under the guidance of Ric Stern. Thankfully for Ric he has helped me out tremendously to be able to use this powerful tool....

Never go anywhere without the Powertap whilst riding. Really easy to spot days when I am suffering as the power is way off.

Rob
 
Ric:

Just click on 'IMG' amongst the buttons above where you insert your reply. Then enter the url where the image is stored.
 

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