So I just got a power meter..

RutlandGav

..I've been commuting to work the past four years but recently started to kick things up a notch by

a) getting this lovely comfy, stable gravel bike that even i can't crash (yet)
b) subscribing to Katie Kookaburra's YT channel
c) getting the power meter (finally!)

First impression - holy crap this thing eats batteries. Got 8 hours out of the first set - going to have to include button cells in my puncture kit from now on.

Second Impression - maintaining a set power level is much , much more difficult than on an exercise bike at the gym.

I've set the Garmin to show instantaneous power and 10 sec average. On my long distance cruise pace, i've got a tendency to hunt between 150-200W, over about a 10 second cycle. Paying close attention to the instantaneous output to try chase the target doesn't help much (just induces sharper, shorter duration fluctuations in power) possibly because of the response lag, it also is likely to make me stick it in a tree because i'm never looking where i'm going.

https://imgur.com/kd4eNVm


So today I set out to try and get an idea of my aerobic threshold power. I am aware the accepted method is to go as hard as you can for 20 minutes and take 95% of your average. Of course this not only measures your aerobic power but also how much oxygen debt you are able to run up, hence taking 5% off for that.

I thought I could measure my aerobic power by going at a constant wattage and seeing if my HR is staying steady - if it is, I'm aerobic, if it trends ever upward the longer the test continues, i've probably slipped into the red. My inability to be consistent hampers this, though when i can add a Garmin compatible HRM so HR appears on this graph it might become clearer.

I used to do this kind of test on gym exercise bikes, and holding a constant wattage was easy, but i got very low numbers - 140w reported - i think the Lifecycle machines they have grossly underestimate.

The first graph is me trying to hold 200W, my HR was 148 at the beginning and end of that period. Then I tried targeting 210W, but due to my inaccuracy in target power it was futile attempting a change that small, instead i ended up going for 220W, which is the second graph.

Within a minute, my HR was up to 157. A minute later, 159, then after another minute was showing 162. I had a camera going and was calling out numbers into it at intervals.. at the start of the 220W I was ok, commenting into the camera about numbers seen, by the end i was panting hard and only calling out the HR as the minute rolled round. As I'm 46, this is not that far from my max HR and it seems unlikely, given how fast my hr was going up, i could sustain that for 20 minutes anyway. So I think it's fair to say my FTP is between 200W and 210W ATM.

I take it this kind of inconsistency is normal, but my main reason for getting the power meter was to better manage my pacing in the face of headwinds/gradients etc. As I understand it, the transition from fat to glucose burning is nonlinear, so if you're trying to hypermile your glycogen constant power is an advantage. My weight loss journey through cycling is almost complete but i'd like to get into Audaxes, hence the hypermiling. I want a decent average speed but not have to consume so many calories per hour on bike that i get queasy, it really ruins your enjoyment of a ride.

OnTheRopes

actual power (instant) is really not very usable on the road, 10 second average is too slow.
Personally I have 2 power displays up for intervals, 3 second average and lap average. 3 second gives a quick view of actual output and lap average is what you need to work to for an interval. So for example do 2 minute intervals at your AC, so if that is 400 watts, hit the lap button as you start the interval, the 3 second sows if you are above or below the avwerage, the average is what you want to work towards for the interval. If that makes sense?

StillGoing

What power meter and has it been calibrated? Shouldn't be eating batteries at that rate either. My P2M Type S lasts for months. You do know that your FTP should be a sustainable power that you can hold for the full 20 minutes rather than going flat out for 20 minutes and tailing off as you fade before the end?

I'd PM Alex Simmons re your method for his view.

aberdeenal

If you're serious about using your new PM, I would highly recommend Training and Racing With A Power Meter by Hunter Allen and Andrew Coggan

cougie

I found that power meters are brilliant for turbo training but much trickier outside to stick to. Weather and roads and traffic just mess it up.

I save outside rides for fun now.

RutlandGav

philthy3 wrote:

What power meter and has it been calibrated? Shouldn't be eating batteries at that rate either. My P2M Type S lasts for months. You do know that your FTP should be a sustainable power that you can hold for the full 20 minutes rather than going flat out for 20 minutes and tailing off as you fade before the end?

I'd PM Alex Simmons re your method for his view.

Garmin Vector 3 pedal. There is an option to calibrate before every ride on the Edge 520 bike computer, and I've told it the crank arm length. I saw some professional reviews of this meter saying they were only getting 20 hours not the claimed 100. The batteries are tiny LR44 coin cells (two thereof). Cost £4 a pair at my local supermarket but that's outrageous, they might look like hearing aid batteries but there's no silver, lithium or pixie dust in them. They're just standard 1.5v alkaline chemistry like an AA but tiny.

I've been fiddling about trying different Garmin mounts and may have been inadvertently waking the device from sleep mode.

pblakeney

RutlandGav wrote:

Cost £4 a pair at my local supermarket but that's outrageous, ..

First mistake right there.
Go on line and find out how much you were ripped off by.

StillGoing

RutlandGav wrote:

philthy3 wrote:

What power meter and has it been calibrated? Shouldn't be eating batteries at that rate either. My P2M Type S lasts for months. You do know that your FTP should be a sustainable power that you can hold for the full 20 minutes rather than going flat out for 20 minutes and tailing off as you fade before the end?

I'd PM Alex Simmons re your method for his view.

Garmin Vector 3 pedal. There is an option to calibrate before every ride on the Edge 520 bike computer, and I've told it the crank arm length. I saw some professional reviews of this meter saying they were only getting 20 hours not the claimed 100. The batteries are tiny LR44 coin cells (two thereof). Cost £4 a pair at my local supermarket but that's outrageous, they might look like hearing aid batteries but there's no silver, lithium or pixie dust in them. They're just standard 1.5v alkaline chemistry like an AA but tiny.

I've been fiddling about trying different Garmin mounts and may have been inadvertently waking the device from sleep mode.

The fact that you're using pedal mounted power measurement will account for some differences in the power from your gym bike sessions. The pedals are the first point of the power measurement followed by the crank arm, spider and hub. The further you go along the chain line for measurement, the greater the loss of power.

You pedals are faulty or the batteries cheap knock off rubbish to be only getting 8 hrs out of them even with inadvertently waking them up.

sungod

RutlandGav wrote:

...
I take it this kind of inconsistency is normal, but my main reason for getting the power meter was to better manage my pacing in the face of headwinds/gradients etc. As I understand it, the transition from fat to glucose burning is nonlinear, so if you're trying to hypermile your glycogen constant power is an advantage. My weight loss journey through cycling is almost complete but i'd like to get into Audaxes, hence the hypermiling. I want a decent average speed but not have to consume so many calories per hour on bike that i get queasy, it really ruins your enjoyment of a ride.

there's a limit to how fast you can burn fat, afaik it remains pretty constant as effort increases, but burning glycogen rises with effort

there's a metabolic limit to how much your can digest+absorb, for glucose c. 60g/hr, for fructose c. 30g/hr (these are typical figures quoted, people vary), they use different pathways

ignoring other sources that're slower to digest...

for sugars c. 4 kcal/g, if you assume 90g/hr for this glucose:fructose mix you'd be getting c. 360 kcal/hour

there's no point eating more per hour than you can absorb, stick to the easiest to absorb as you ride, imo there's no reason to get queasy with good selection

...this is using typical values and avoiding factoring in other potential sources like fat, c. 9kcal/g, but there's a limit to how much fat you'll want to eat per hour

ethanol at c. 7kcal/g might seem an option, but it gets burned preferentially vs. existing fat, and might cause you to fall over

RutlandGav

sungod wrote:

there's a metabolic limit to how much your can digest+absorb, for glucose c. 60g/hr, for fructose c. 30g/hr (these are typical figures quoted, people vary), they use different pathways

ignoring other sources that're slower to digest...

for sugars c. 4 kcal/g, if you assume 90g/hr for this glucose:fructose mix you'd be getting c. 360 kcal/hour

there's no point eating more per hour than you can absorb, stick to the easiest to absorb as you ride, imo there's no reason to get queasy with good selection

Makes sense. That ride i got queasy, I'd drunk a load of rather concentrated Vimto (barely diluted) and had some dried pitted prunes in my frame bag, so 100% of the energy was in the less digestible form of fructose, pretty much. Will get some high 5 powder before attempting any events then..

RutlandGav

https://www.strava.com/activities/2463197905/overview

Well, the following morning, I woke up a bit early so decided to get some Power Meter data from a long ride.

Ride time 7.15
Dist. 92.5 miles
Climbed 1078m
Avg HR 120
Avg power 143W
Calories 3568

I set out before breakfast with a litre of fruit juice and a 500ml sports drink in my bag, planning to consume 200 cal/hr. For the first two hours I was doing about 180 watts, hr 135. After that I realised this might be too fast and was starting to feel my energy levels decreasing, so eased up to 160.

At this point, I am also suspecting something odd about the residents of the South Kesteven district. They don't appear to eat food. Village after village went by with the odd antique shop, but nowhere that would sell you so much as a can of coke. They could all be daywalkers.

By hour four I was out of drink and lowered my pace again to 150 watts. I'd ask some locals about their shop. Oh it closed last year, you'll have to go to XYZ, two miles that way, they've still got one i think. Rinse and repeat. I reached Rutland water reservoir after 5 hours. By this point I should have covered 45 miles but due to getting lost and detours the trip meter was showing 55, i'd not drank anything for 90 minutes, and we were in a torrential downpour that was forecast to continue for another 5 hours. The original plan included the path that circuits the perimeter of the reservoir, but it had become a quagmire and they also had sheep grazing there, mud and animal droppings were flicking off the tyres onto my head. I decided to skip this part of the trip but ended up doing two miles of the perimiter path anyway in search of a cafe that, once again had closed down. By this point i was no longer looking at the power and was just hanging on. I eventually decided I was better off accepting a detour into a large town than chase these endless mirages, and finally found the holy grail, a petrol station, 5 and a half hours into the ride. By this point i was in energy deficit to the tune of 1900kcal.

Consuming 685 kcal in a matter of seconds, i set off again just as the skies cleared. I had the Garmin nav me home via the most direct route, and felt fresh again , holding 180 for an hour before dropping to 160 for the remainder of the journeys. I had another 450 available from my gas station purchases and continued to take little drink breaks, but they didn't really perk me up again - guess my stomach was already absorbing as fast as it could. Felt very tired on the last half an hour. After my post ride meal I ended up taking a 3 hour nap.

Looks like with better nutrition i could have maintained 160W the whole way? I feel completely smashed right now though. Meanwhile Katie Kookaburra (280 FTP!) does 600km then goes home and edits a very professional looking vid..

MiddleRinger

AberdeenAl wrote:

If you're serious about using your new PM, I would highly recommend Training and Racing With A Power Meter by Hunter Allen and Andrew Coggan

^^ This. A very thorough read (sometimes too much info) and well worth reading cover to cover.

Maintaining a power range outside becomes a little easier once you get used to it, but at first it's very surprising just how much your power varies with the slightest change in gradient, direction, wind, road surface, etc. Much harder than on a turbo trainer with fewer variables.

markhewitt1978

cougie wrote:

I found that power meters are brilliant for turbo training but much trickier outside to stick to. Weather and roads and traffic just mess it up.

I save outside rides for fun now.

I've found exactly the same, on the likes of Zwift it's great but even when you employ 3 or 5 second smoothing outside it's still too all over the place to be of any practical use. Perhaps good for determining your effort level post-ride but not massively useful during the ride itself.

kingstongraham

markhewitt1978 wrote:

cougie wrote:

I found that power meters are brilliant for turbo training but much trickier outside to stick to. Weather and roads and traffic just mess it up.

I save outside rides for fun now.

I've found exactly the same, on the likes of Zwift it's great but even when you employ 3 or 5 second smoothing outside it's still too all over the place to be of any practical use. Perhaps good for determining your effort level post-ride but not massively useful during the ride itself.

Traffic messes it up, but when on a climb, it is great to ensure you don't set off too hard, and start to struggle.

The reverse is also true, it can mean you become aware of when you are easing off because the gradient changes, and encourage you to push harder.

I only have 3 second power displayed (plus speed), anything else is not controllable enough when on the move.

RutlandGav

KingstonGraham wrote:

Traffic messes it up, but when on a climb, it is great to ensure you don't set off too hard, and start to struggle.

The reverse is also true, it can mean you become aware of when you are easing off because the gradient changes, and encourage you to push harder.

I only have 3 second power displayed (plus speed), anything else is not controllable enough when on the move.

I think I need to re-learn what I used to do, ie. listen to my legs very carefully, and sense check on the PM. I find if i press as hard as i can without getting the beginnings of a lactate burn at the end of the stroke, and push the cadence as high as possible while maintaining good form, that'll be somewhere between 180-200W. 200W is comfortable but requires intent concentration so i don't take little mini breaks that pull the average down.

tonysj

Just a little something that may help you. I always have the Emma Pooley Oaty banoffee pint of goodies for breakfast per-ride when I'm doing a long ride (50 miles +). Check you tube to find ingredients and how to make it the night before.
Power meter readings are up and down during a ride. If you have a turbo trainer do the FTP on that and put that number into your Garmin.
I have power on 3 second smoothing, % of FTP plus others on my display but tend to ride by Power and % of FTP. I think if you get your FTP sorted then that will help you with your effort levels.
Everyone's got their ideal method on fueling during a ride but I tend to just take 1 or 2 bottles of water mixed with squash and a pinch of salt. Odd bits of food/snacks during the ride. Very rare for me to have a gel but make sure you wash it down with water/drink to dilute it.

RutlandGav

TonySJ wrote:

Just a little something that may help you. I always have the Emma Pooley Oaty banoffee pint of goodies for breakfast per-ride when I'm doing a long ride (50 miles +). Check you tube to find ingredients and how to make it the night before.
Power meter readings are up and down during a ride. If you have a turbo trainer do the FTP on that and put that number into your Garmin.
I have power on 3 second smoothing, % of FTP plus others on my display but tend to ride by Power and % of FTP. I think if you get your FTP sorted then that will help you with your effort levels.
Everyone's got their ideal method on fueling during a ride but I tend to just take 1 or 2 bottles of water mixed with squash and a pinch of salt. Odd bits of food/snacks during the ride. Very rare for me to have a gel but make sure you wash it down with water/drink to dilute it.

Looks tasty. The food's alright as well.

Anyway, 48 hours later I get out again and log my first Strava 100 miler. This time I did not run out of food. Went through 6 bottles of Lucosade sport, and brought 2 packs of glucose tablets in case I started consuming any food that's not purpose designed bike fuel to get the glucose:fructose ratio where it should be. Ate about 2/3 of a pack of Salt n Vinegar Snack Jacks (rice cakes) at destination and a FRIJJ milkshake. A soreen malt loaf on departure. Average power up from 133 to 147 despite being a longer ride, would have been higher still had my power meter not kept dropping out and recording zeros. Not as sore afterward too.

https://www.strava.com/activities/2469416651