Poll: L/R Powermeter V One Leg Only

pprendeville

Would you value a left/right powermeter over a one leg output powermeter provided it was accurate and cost effective.

Leroy42

pprendeville wrote: »

Would you value a left/right powermeter over a one leg output powermeter provided it was accurate and cost effective.

That's the important part. It all depends on the costs and the value you place on it.

SRM should really be the only PM that anybody uses, it is the gold standard. But not everyone can afford them and therefore a different approach is used to try to gain reliable information at a cost that is more 'value' to a bigger market.

manwithaplan

Is left/right power balance any use as an additional data item? In my view, no. I have left/right power on my PM and, apart from providing some reassurance that my busted hip hasn't affected me unduly, I can't say it's much use for anything. Even if I found a bit of an imbalance, I don't think there's a whole lot I could do about it. So to answer your question, if a one legged PM was accurate, it would do the job for me.

The question is whether a PM that takes its reading from a single pedal or crank is sufficiently accurate. I haven't a clue about that to be honest.

nilhg

manwithaplan wrote: »

Is left/right power balance any use as an additional data item? In my view, no. I have left/right power on my PM and, apart from providing some reassurance that my busted hip hasn't affected me unduly, I can't say it's much use for anything. Even if I found a bit of an imbalance, I don't think there's a whole lot I could do about it. So to answer your question, if a one legged PM was accurate, it would do the job for me.

The question is whether a PM that takes its reading from a single pedal or crank is sufficiently accurate. I haven't a clue about that to be honest.

Do you find that your L/R balance changes either as power output goes up or as you get tired?

fat bloke

I see what you did there.

I think one poll, and one leg, is perfectly sufficient...

victorcarrera

pprendeville wrote: »

Would you value a left/right powermeter over a one leg output powermeter provided it was accurate and cost effective.

Neither! If absolute power measurement is not important to you and you only need to record and analyse your intervals and pre season improvement in relative power/time you can reduce the cost and eliminate all of the (pedal, crank,hub) measurement errors associated with dedicated pm's by using a cadence counter while working against a known resistance on a turbo.
I use an edge 705 for this with display set to cadence and hr (to keep me honest) and just check the cadence count after the session. It only takes a few sessions to work out and get used to the different gearing and resistance settings for the different intervals. (No need to write them down. You will remember them.:D)
I worked out the error rate for an average cadence of 90rpm as follows.
(The error is calculated based on mistiming one rpm while stopping the clock)
Minutes % Error rate
1..... 1.111%
3..... 0.370%
5..... 0.222%
10..... 0.111%
20..... 0.056%
60..... 0.019%
I can't think of anything else and using the turbo eliminates all the other variables and interferences you might meet on the road.

Zippe

pprendeville wrote: »

Would you value a left/right powermeter over a one leg output powermeter provided it was accurate and cost effective.

Hey,

I looked at left leg power, I just don't think they are the way to go, you will never get a honest power output, SRM is the god of all pm's but price is just to hight for most,I have power tap's and a power2max on my tt bike as I like power on my tt racing, the power tap is handy to swap from bike to bike for training, both will give you a total power, I looked at the left leg power but if your right leg is getting stronger you won't know, if your on a budget for training I'd say power-tap if you like power for racing power2max or quarq, you could go power-tap but I thing cranks are better or if you want to go mad on training toys the wattbike is a nice toy, I've used one good few times now and plan in getting one for myself next month, but back to the question I think cranks or wheel pm is far better than left leg,

Cheers zip,

Beasty

Used to be pretty close - 50:50 or 49:51 either way for most rides as well as on the Wattbike. Since my crash I've typically been recording maybe 45/47:55/53

That info means I'm pretty sure I have a bit of improvement left in the left leg and can try and work to deliver that improvement. I am therefore finding that info invaluable

doozerie

pprendeville wrote: »

Would you value a left/right powermeter over a one leg output powermeter provided it was accurate and cost effective.

If the cost (and quality) of a left/right powermeter was comparable to that of a one-leg-only powermeter, I'd go for the former without hesitation. The usual dramatic difference in prices makes it a much harder choice though.

One appeal of a left/right powermeter is simply to satisfy my curiosity about my left/right balance - that might seem frivolous, but with my modest abilities on a bike a powermeter isn't going to transform me into a fantastic rider anyway so any powermeter is arguably frivolous for me.

However, if my balance is so far out that I am over compensating in one way or another, even subtly, then I might be gradually building longer term problems for myself if I don't identify and address that. For example, I have a minor lower back issue from many years ago, an imbalance on the bike could exacerbate that and turn a minor irritation into something more significant over time.

victorcarrera

doozerie wrote: »

...
However, if my balance is so far out that I am over compensating in one way or another, even subtly, then I might be gradually building longer term problems for myself if I don't identify and address that. For example, I have a minor lower back issue from many years ago, an imbalance on the bike could exacerbate that and turn a minor irritation into something more significant over time.

I have a suspicion that the left/right imbalance recorded by many TT and interval testers is down to exhaling in sympathy or harmonic with the down stroke of the preferred (stronger) leg. This is a well known and practised technique in many other speed and power sports. It may also be the case that it doesn't matter in cycling due to other physiological and psychological limiting factors of individual cyclists.

joey100

I have a power2max on my bike. It gives a L/R breakdown afterwards. Not sure how it does it tho. I was half thinking of getting a stages at the start and to be honest I'm glad I didn't now. I've looked back at my training on it and most Thursdays I've done an easy hour on the turbo. Left right breakdown is different in pretty much every one, and doesn't stay consistent across the full hour. On pretty much all efforts the left right balance varies at different points. If I was working off left only and doubling it wouldn't give me an accurate number and more importantly wouldn't be consistent across my training. Some hours are 47% left, 53% right, I've had one go as high as 44% left, 56% right, for the same NP at the end. If I was on the stages these would have been different outcomes with less power being doubled the in the second hour.

Inquitus

joey100 wrote: »

I have a power2max on my bike. It gives a L/R breakdown afterwards. Not sure how it does it tho. I was half thinking of getting a stages at the start and to be honest I'm glad I didn't now. I've looked back at my training on it and most Thursdays I've done an easy hour on the turbo. Left right breakdown is different in pretty much every one, and doesn't stay consistent across the full hour. On pretty much all efforts the left right balance varies at different points. If I was working off left only and doubling it wouldn't give me an accurate number and more importantly wouldn't be consistent across my training. Some hours are 47% left, 53% right, I've had one go as high as 44% left, 56% right, for the same NP at the end. If I was on the stages these would have been different outcomes with less power being doubled the in the second hour.

P2Max estimates L/R balance, it doesn't measure it, DC Rainmaker found it measured 90/10 when pedalling with one leg for instance, maybe you could test that out on the Turbo for us. Anyways long and the short of it is the data doesn't mean much.

tunney

Units that measure from one leg technically aren't powermeters.

A meter is something an instrument that shows the extent or amount or quantity or degree of something.

It measures in other words.

A one leg unit guestimates total power.

Inquitus

tunney wrote: »

Units that measure from one leg technically aren't powermeters.

A meter is something an instrument that shows the extent or amount or quantity or degree of something.

It measures in other words.

A one leg unit guestimates total power.

This is true, but if your L/R balance is fairly consistent it guestimates it in a fashion that is more than adequate to do accurate, targeted and repeatable power based training. For most amateurs it will be more than sufficient and in alot of cases the results will not be materially different from a crank or hub based solution.

It's a case of is the cost saving justified by the immaterial difference in the likely results. Everyone has their own answer to that question.

manwithaplan

nilhg wrote: »

Do you find that your L/R balance changes either as power output goes up or as you get tired?

Strangely, my dodgy leg seems to contribute less at low power output, maybe 47%. It's more or less level as power output increases. Haven't observed any changes with fatigue. There is a little less muscle mass on the previously injured side, mainly at the knee end of my quad. I do a little work on that in the gym, mainly for future functional purposes rather than specifically for cycling.

CramCycle

victorcarrera wrote: »

I have a suspicion that the left/right imbalance recorded by many TT and interval testers is down to exhaling in sympathy or harmonic with the down stroke of the preferred (stronger) leg. This is a well known and practised technique in many other speed and power sports. It may also be the case that it doesn't matter in cycling due to other physiological and psychological limiting factors of individual cyclists.

I don't think this would apply to cycling due to the simple fact of cadence, even when low, would be faster than breathing rate. I imagine that attempts to do so would limit oxygen uptake?