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PostPosted: Mon Apr 28, 2014 2:18 pm 
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Hi all,

Some of the recent Power Meter discussion such as the Normalized Power thread and various Stages Power Meter Love/ Hate threads have gotten me thinking about introducing Power to improving my MTB riding.

The events I tend to do are 4-6 hours and this Summer I’ll mainly be doing lap based 6 hour races as it is what I enjoy most. I’m planning to start XC racing next Winter to try something new, travel a bit more and explore some different trails (but hopefully not totally suck whilst doing so!).

I have also been using Trainerroad’s Virtual Power over the winter and can full appreciate the merits of using Power to make more specific and more efficient gains on the bike. I appreciate the limitations of the Virtual Power approach but as a training tool I’ve found it incredibly useful if you take it for what it is. My riding ability has really jumped up since training by Virtual Power on Trainerroad. For those of us without unlimited riding time it makes sense to make the most of the time we do have!

My question however, is how useful is an actual Power meter for XCO/ XCM racing and training in terms of outdoor rides? Training indoors is one thing but I imagine outdoors MTB rides are a whole different kettle of fish. The main issue being that the technical nature of MTB course prevents nicely structured, constant efforts and when racing it is pretty much all out or nothing and going flat out on the terrain in front of you. Benefits I (naively) anticipate from using a Power Meter for outdoor MTB rides/ races is:

Better understanding the demands of different rides and races
Better understanding my strengths and weaknesses relative to different rides/ races
Improved pacing over long (6 hour +) races
Improved monitoring of training load over a week/ month/ etc
Improved reliability of indoor training by Power vs Virtual Power
Improved definition of FTP and power profiles for improved indoor training based upon additional outdoor data

I’ll never be a world beater but I love MTB and getting faster and fitter is super rewarding. So, are the demands of MTB racing too variable to get too much out of a Power Meter and should I just stick to Trainerroad indoors and just get on and ride outdoors or is a Power Meter going to be an extension of the gains I’ve made indoors using virtual Power on Trainerroad and another revelation for my riding?

Any help or thoughts are very much appreciated!

Many thanks, Dan


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Posted: Mon Apr 28, 2014 2:18 pm 


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PostPosted: Mon Apr 28, 2014 2:42 pm 
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I should expand on my original post to say that what prompted this question was firstly seeing the benefits of training by power on Trainerroad and secondly wondering how current analysis techniques and softwares translate to MTB? I do not doubt for a second the merits of training by power but presumably most if not all of the analysis and software comes from steadier road type riding.

Image

The figure above if from http://www.fascatcoaching.com/mtbpower.html and got me thinking about how useful or practical a Power Meter actually is for outdoor MTB riding and racing. I'm guessing the NP and consequently TSS and IF calculations for example will be a poor reflection of the work done on the MTB since there's a massive difference between 2 hours of short hard bursts and 2 hours at the power that NP suggests was the "average" over that duration. Add on top of that, that these bursts may well be 80rpm high power outputs which will presumably have a difference in muscle fatigue compared to the same power delivered smoothly at 100rpm on the road. The physiological demands will be very different in all these cases so I'm wondering really how well the demands of outdoor MTB can be understood for the purposes of monitoring training load/ pacing/ etc in standard software and analysis techniques?

On the Cycleops site http://www.cycleops.com/en/training/training-resources/225-using-intensity-factor-to-train-in-the-right-zone.html they mention monitoring the IF for each lap as a means of pacing. They seem to be suggesting that smoothing the power surges in MTB using NP then IF is helpful from a pacing point of view but my initial reaction is that you wouldn't be getting a true representation of the efforts and what is sustainable by smoothing the many peaks during MTB. Or, is it just a case that some smoothing is inevitable and the IF number itself is somewhat irrelevant, but more that it is a number for relative comparisons for pacing? A bit like Virtual Power vs actual Power I guess, where the numbers don't matter, just how those number change?

One of the other Cycleops articles http://www.cycleops.com/en/training/training-resources/96-deciphering-off-road-power-graphs.html refers to using energy expended for pacing which makes more sense to me. It also has some nice details on making a Power Meter relevant for MTB...

I guess what I'm getting at is how useful or limited is a Power Meter for MTB and what are the tricks or common approaches to not misinterpreting the data and actually getting useful stuff out


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PostPosted: Mon Apr 28, 2014 4:31 pm 
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Don't go down the rabbit hole of FTP and NP. Do some research on what anaerobic vs aerobic really is. If you accept the concept that "FTP" is not fully anaerobic or aerobic, then working on power when anaerobic will be the most effective method of increasing power at any longer length of time. Unless you are doing long climbs MTB is very peaky and the efforts tend to be short in nature. Training based upon an hour long steady effort does not make much sense. The shorter the interval the more useful power becomes, because of the lag in HR. Not that HR in a short interval is not useful. If your HR does not get to AT at the end of an interval it is a signal of fatigue. Here are a few links that may be helpful for you.
http://www.coachr.org/lactate.htm
http://www.enhancedfp.com/sport-specifi ... y-thibault
http://www.training4cyclists.com/killer ... r-vo2-max/
http://www.bicycling.com/training-nutri ... e-interval


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PostPosted: Mon Apr 28, 2014 5:13 pm 
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for me, my PM is useful for several things, some of which you noted:

- analyzing the race demands
- would be useful for longer events pacing (im not doing such events though)
- absolute best training tool on the road. In fact, I do all my training on the MTB on the road. All intervals are done on the MTB to get as familiar as possible with my fit and position.
- getting to know the actual energy expenditure of long trail rides is useful for post-workout nutrition.

I do not really work with NP, etc. Sure average power is pretty useless for MTB riding and racing but there are a whole lot of other useful information you can get from a PM while racing MTB. I do not tend to use it while racing though, I do not focus on the power during the race but use the tool as post-race analysis.


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PostPosted: Mon Apr 28, 2014 6:16 pm 
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DanW wrote:
Improved pacing over long (6 hour +) races


Actually for *any* race longer than 5 seconds.

All the items on the list are valid, but this one stuck out because you also said that in races you "just go all out".

If you do, you are making a big mistake. IME MTBers usually pace like shit. I jumped into the last lap of the freakin MTB national championships over 20 years ago, on the longest climb. I suck, but I passed over 20 guys and made it up to 5th place by the top, right behind John Tomac. The only reason I could do that was because all of them were totally wasted by that time... because they rode way too hard in the beginning.

Of course if you are on a route where it is really hard to pass, there may be a good reason to get to the front. Not having to eat dust is another reason. But if you aren't going to be a front runner anyway, you'd probably gain a lot by letting everyone go ahead and spend the day passing riders as they blow and fade...

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formerly rruff...


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PostPosted: Mon Apr 28, 2014 6:30 pm 
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JimV, thank you for the excellent links. I am learning more and more every day and Weightweenies is an excellent resource of fast and knowledgeable people :D

My real question though is how would a PM on the MTB help compared to training using the Virtual Power feature of Trainerroad indoors? Vincent mentions a valid point of specificity of fit and position completing intervals outside but I would probably tend to do most interval stuff indoors where variables are easy to control and the convenience of not getting soaked in the beautiful UK weather for a least a few days a week is high :D

I am absolutely sold on training by power but can not visualise how the use of a PM outdoors on the MTB would be. Basically, what would I be gaining with a PM that I can't already do using training indoors with Trainerroad's Virtual Power?

Quote:
for me, my PM is useful for several things, some of which you noted:

- analyzing the race demands


What can you understand that elevation and HR data doesn't tell you? A Garmin for example will tell you how long and demanding a climb is (HR, so long as HR has time to adjust) for example and I guess you know at the time of the race where you are strong compared to the other guys and where you might be lacking slightly. Is it from the point of view of showing the numbers you hit for various durations to better inform interval training?

Quote:
- would be useful for longer events pacing (im not doing such events though)

- getting to know the actual energy expenditure of long trail rides is useful for post-workout nutrition


How do people tend to do this? Is it literally a case of looking at energy expended in kj per hour? Also links in to...

Quote:
I do not really work with NP, etc. Sure average power is pretty useless for MTB riding and racing


So that kinds of throws out monitoring IF lap to lap as Cycleops suggests in the link above and also makes monitoring training load over weeks and months tricky I guess. To be honest I don't really pay too much attention to this anyway in Trainerroad with virtual power so I'm not sure if people use this aspect of a PM for MTB outdoors too?

Thank you ever so much for all of the help and comments. I am trying to visualise just how useful a PM would be for the longer races I'm currently doing (and future XCO) and if it adds anything significant I can't already glean from using Virtual Power in Trainerroad and understanding outdoor rides from the usual Garmin data...


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PostPosted: Mon Apr 28, 2014 6:38 pm 
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Quote:
All the items on the list are valid, but this one stuck out because you also said that in races you "just go all out".

If you do, you are making a big mistake. IME MTBers usually pace like shit. I jumped into the last lap of the freakin MTB national championships over 20 years ago, on the longest climb. I suck, but I passed over 20 guys and made it up to 5th place by the top, right behind John Tomac. The only reason I could do that was because all of them were totally wasted by that time... because they rode way too hard in the beginning.


Sorry, I didn't mean in reference to the longer races and "go all out" is a relative thing between a 1.5 hour XCO race and 6 hours race. Of course there is pacing involved but I guess is less subtle in XCO than XCM. On the courses we tend to have there aren't long climbs and the technical sections give something of a breather before the next hard effort. Probably a valid point to include pacing as a PM benefit in the shorter races although it is interesting that Vincent mentioned he doesn't look at the PM at all during XCO


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PostPosted: Mon Apr 28, 2014 10:16 pm 
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It sounds like the real question you are asking is can you do quality workouts outside on a MTB. I think that depends on terrain. For ease of pacing I tend to do all of my intervals on flat road with a head wind. I live in a very flat part of the world so I don't believe that I could do a quality workout from a fitness stand point off road. That said your best efforts will come from your races, so having power data from those would be valuable to evaluate your progress.


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PostPosted: Mon Apr 28, 2014 11:41 pm 
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Dan

when anylising the race file, I will look at several things

- laps duration
- how many times I hit, eg. 500W for at least 5 seconds
- best 1-2-3-4-5min power as well as 5-30sec too
- race energy expenditure
- key climbs and key ''power'' section of the course, looking at the average power and comparing from lap to lap, to see if I was consitent and if pacing was good.
- time in zones for the race, especially looking at power above FTP to have an idea of the sort of physiological stress I put on myself and recovery implications.

As for expended kJ, it pretty much comes down to 1kj = 1kcal so for a 2500-300kj ride I know I gotta eat plenty and glycogen is likely low.


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PostPosted: Tue Apr 29, 2014 10:55 am 
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Quote:
It sounds like the real question you are asking is can you do quality workouts outside on a MTB. I think that depends on terrain. For ease of pacing I tend to do all of my intervals on flat road with a head wind. I live in a very flat part of the world so I don't believe that I could do a quality workout from a fitness stand point off road. That said your best efforts will come from your races, so having power data from those would be valuable to evaluate your progress.


I don't think I envisage doing the focused intervals outside vs the control inside but I suppose this might be something of a revelation if I were to end up with a PM... I'm not sure

I think I'm approaching it more from "I am happy with virtual power and doing short focused intervals indoors, but would I gain a significant amount by having a PM for during and after outdoor ride/ races?"

My first thoughts on a PM were on the benefits of tracking how much each outdoor ride and race is taking out of me and how to plan recovery better as much as how to better plan the actual riding. Seeing threads like the NP one here on WW go me thinking though that understanding MTB with the bog standard measures such as NP/ TSS/ IF probably don't apply all that well due to MTB's "peaky" nature.

I do like the idea of the best efforts coming from races though and being the best check of progress (or not!). A bit like Vincent mentions keeping track of the best 1-2-3-4-5min power as well as 5-30sec too. It is really helpful to see what info people might use during a longer race but also look at afterwards and monitor progress too. Thank you for the pointers!


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PostPosted: Tue Apr 29, 2014 12:58 pm 
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Devinci's analysis of a race file is right on. When analyzing a race file or interval file you don't spend much time looking at overall averages. I spend time looking at histograms as well as time spent at various power levels. For intervals you can look at the shape of the power output, did you hit it hard and fade or was it a even effort. A PM is not the be all and end all of training tools, but it does add a lot of precision. It can help take the guess work out, was I tired or did I give up or did I make a big improvement.


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PostPosted: Mon May 05, 2014 8:31 pm 
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I think the PM will show you exactly what you are doing, so that you can "manage down" spikes which would have been 500W to below your AT, then it will help you to pedal much harder on the easier parts. In total you will go noticeably faster, probably with less pain.


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PostPosted: Wed May 07, 2014 1:58 pm 
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For me, my MTB powermeter is just as important as the road powermeter due to the race data I get. I don't normally do intervals on my MTB, but having the data from races is really good to have and analyze. I don't use it a whole lot racing except down 2 tracks or big climbs.


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PostPosted: Mon May 12, 2014 1:37 pm 
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I have an MTB system, but I tend to use it for winter Intervals more than for MTB. Most people I know with SRM MTB still do most of their training on the road. As an enduro rider, there may be some advantage to you in pacing, too.


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PostPosted: Mon May 12, 2014 2:44 pm 
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WMW wrote:
If you do, you are making a big mistake. IME MTBers usually pace like shit. I jumped into the last lap of the freakin MTB national championships over 20 years ago, on the longest climb. I suck, but I passed over 20 guys and made it up to 5th place by the top, right behind John Tomac. The only reason I could do that was because all of them were totally wasted by that time... because they rode way too hard in the beginning.
FFS, 20 year old anecdote brought bang up to date........ :lol:
If you look at lap times now (as in this year, not 1994) they'll usually be within a few percent over the course of a 6 or 7 lap race. MTBers use powermeters and HRMs for training these days as well. These days, after the initial flurry of activity, they'll probably be pacing almost as well as any TTer, as most racing is either on your own, or in very small groups, so you are almost completely reliant on your own power output.

And at that level (Nationals, elite racing) you have to go hard at the start or you immediately put yourself out of the group who can win. On a properly technical course, 20 or 30 places back on the first singletrack might put you 3-5 minutes down if just one muppet stops.

And to the OP, i've looked at PMs for racing MTBs many many times, and tbh, the nature of XCO racing is such that i think my money would be better spent on a PM for my training bike. If i was only racing XCM, it'd be a toss up. I suppose its similar to the difference between racing crits and timetrials, one is all about going with the moves, not letting gaps open up and if you have to go into the red too often, you weren't fit enough, or strategically minded enough for that race.

The other is about pacing yourself to the line and collapsing somewhere within hobbling distance of the changing rooms.


Last edited by mattr on Mon May 12, 2014 2:54 pm, edited 1 time in total.

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Posted: Mon May 12, 2014 2:44 pm 


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