How to pace intervals with a powermeter

p929

Hi,

Although I'm only 1 year on cycling I decided to buy a dual side powermeter 1 month ago in order to improve my training. Before the purchase, I had read and watch videos about training zones and it seemed as 'easy' to pace the intervals a I used to do with my HR, the only difference would be that the value would have an instantaneous response and not been affected by weather, temperature, as HR is.

However, since I did my FTP test I realized how hard is to keep the power output within a small range when performing intervals. For instance, my Z3 (tempo) should be 160-192W. It's a very narrow 32W band, but every time I'm on the bike I can see how the values jump around all the time below/on/ and above the required zone. Nevertheless, I always to keep the the average power within the training zone, and NP usually agrees with the AP.

I have tried to control power by shifting the best I can trying to accommodate to the terrain. OTOH, I found that I can control better the power when I'm climbing, although far from perfect.

Are there any tips from more experienced guys to pace those intervals correctly. BTW I'm using a 3s average on my Wahoo Elemnt, I think that it'd be more complicated pacing the interval when using 5s or 20s averages on the head unit, but if someone thinks otherwise, I'd love to heard about it.

Below is a pic of my last interval training (sweet-spot) showing some statistics.

burnthesheep

What's your cadence look like during that? Rock steady or lots of variation?

The height of the "y axis" for the power is pretty tall for it being only a spread of 250w from max to min. Look at that same time period in Strava and see how it looks. Bet it looks smoother. The graph itself may be making it look bad.

Change the y-axis perhaps.

Here's an over-under interval during a workout I did recently, this graph scale makes it look pretty smooth:

VamP

Set 3s and 30s smoothing on your head unit to help you balance it out. Don't get too worried if you stray out of zone, it's not the end of the world. Most intervals get ridden to what you can do over that period, so use the PM to adjust your initial effort, but it will be self adjusting after that.

kingpinsam

A Cadence of 77 is a bit low, I find it easier to control power output at higher cadences. I would be aiming for closer to 90 RPM for sweet spot.

Looks like you're on rolling terrain with quite a few turns? route is important, I don't do many 20 min intervals outside, but when I do, I've got a loop that only has 2 left turns, and is mostly flat.

p929

thx both for your replies.

@burnthesheep: unfortunately, cadence is not rock steady, as I vary it depending on the terrain trying to keep the power level within range



I know that the Y-axis scale makes it look worse, but I wanted to show how power jumps around from the target zone. Also, on those charts data isn't smoothed by any means, i.e. it's the raw data, probably Strava does smoother it (I don't have an account there, but in GC I can select the seconds to smoother and I prefer raw data always)

@VamP: somewhere I read something similar, i.e. to have both fields on the same screen, but still not clear to me how can I use the 30s average for pacing. At the moment I have 3s and interval average on my page, maybe I should use 3 of them to see if I can learn how to pace.

Did you guys have similar problems when began training with a PM?

p929

kingpinsam wrote:

A Cadence of 77 is a bit low, I find it easier to control power output at higher cadences. I would be aiming for closer to 90 RPM for sweet spot.

I'm also trying to achieve 90 RPM, but opposite to you I find it easier to control power at lower cadences..so maybe I trick myself...maybe I should force me to stay at 90+ RPM

kingpinsam wrote:

Looks like you're on rolling terrain with quite a few turns? route is important, I don't do many 20 min intervals outside, but when I do, I've got a loop that only has 2 left turns, and is mostly flat.

My route has 1-2 turns, but it far from flat, I mean the average gradient is 0.4%, which could be considered flat, but in between there are few small climbs and descents and bumps which increase the difficulty to control power output to me. I can only train outside because I don't have a trainer. It's kinda luxury in a country without seasons and where you can ride outside practically all year.

kingpinsam

That's a very abnormal cadence graph! even out of the saddle I wouldn't be dropping that low, and you ideally don't want to be shifting in and out of the saddle to do sweet spot intervals. I'd try a few rides at a much higher cadence and ignore power for a while, it might take a while but you'll get used to it.

Easier to paste links to specific activities than post a screen shot, but here's a sweet spot one from last year:

https://www.strava.com/activities/831946377/analysis/

If you look at the analysis you'll see my cadence is pretty consistent the whole time. The nature of sweet spot means the power will be a bit more variable - I'm jut aiming at what's comfortable while avoiding going too deep on any rises.

VamP

Yeah I wouldn't worry about cadence too much.

You do get better at putting out a more constant power output, but it is stochastic by nature and there is no evidence to suggest that it is better to deliver power smoothly. Outside is different to turbo, and unless you wish to focus on delivering smooth turbo charts, I don't think I'd worry about it. As someone mentioned, route choice has a big impact over the smoothness. I'm lucky to have a few roads around here that allow 20 minutes more or less constantly uphill, so I use those, but the main thing is to avoid junctions and danger spots.

Having the 30s average on your display gives you a much better idea where your AP is over the last 30 seconds whereas the 3s average is a lot more up and down.

p929

kingpinsam wrote:

I'd try a few rides at a much higher cadence and ignore power for a while, it might take a while but you'll get used to it.

When I performed my FTP tests (the first one was W/O PM so a HRFT) I did keep a more consistent cadence around 90 for sake of repeatability of the test. Maybe I should start with some high cadence drills to improve my technique and that will bump up my power output control.

kingpinsam wrote:

Easier to paste links to specific activities than post a screen shot, but here's a sweet spot one from last year:

https://www.strava.com/activities/831946377/analysis/

If you look at the analysis you'll see my cadence is pretty consistent the whole time. The nature of sweet spot means the power will be a bit more variable - I'm jut aiming at what's comfortable while avoiding going too deep on any rises.

I'm sorry I couldn't check it. I'm probably the only 'cyclist' without a Strava account, probably I should left my asocial behavior and sign up :?

p929

VamP wrote:

I'm lucky to have a few roads around here that allow 20 minutes more or less constantly uphill, so I use those, but the main thing is to avoid junctions and danger spots.

I can have a 1 hour uphill slope (5%), but it'd take me 1 hour to get there, so it'll make my weekdays training too long, but maybe I would try it once a week.

VamP wrote:

Having the 30s average on your display gives you a much better idea where your AP is over the last 30 seconds whereas the 3s average is a lot more up and down.

I'll definitely try it!

sloppyschleckonds

p929 wrote:

I think that it'd be more complicated pacing the interval when using 5s or 20s averages on the head unit, but if someone thinks otherwise, I'd love to heard about it.

VamP has suggested 20s, as will many others

MiddleRinger

p929 wrote:

Did you guys have similar problems when began training with a PM?

Yep. One of the first things you realise is just how much your power output varies ALL the time with every little change in gradient, wind direction, bend in the road, road surface, concentration level, etc. You do get better at being able to hold your power within a wattage range as you go on.

Don't get too hung up on it.

p929

MiddleRinger wrote:

p929 wrote:

Did you guys have similar problems when began training with a PM?

Yep. One of the first things you realise is just how much your power output varies ALL the time with every little change in gradient, wind direction, bend in the road, road surface, concentration level, etc. You do get better at being able to hold your power within a wattage range as you go on.

Don't get too hung up on it.

THX so much for this feedback, I'm glad to hear that I ain't the only one with this issue and that with experience it'll get better. Today I focused a bit more on my cadence, but as you say small bumps on the terrain, slight crosswind, etc vary everything, but I'm willing to improve.

cougie

Much easier to keep at an even pace on the turbo. Outside is tricky.

p929

cougie wrote:

Much easier to keep at an even pace on the turbo. Outside is tricky.

it seems so indeed, but I as I say I don't own a turbo because here I can ride all year long outside having a nice sunny day, OTHO, isn't part of the idea of training with power to be able to pace yourself on a ride/race? I think we have to learn how to pace on real roads 'cause at the end of the day it is where we compite and lacking that skill might be an issue.

However, it might be an interesting idea if one could 'learn' on a turbo how e.g. 200W feels like and later be able to reproduce that exertion of power.

cougie

Your graphs do look very odd. 60-100 cadence ? Power all over the show. It could be you have awkward roads to ride on but it's nothing like mine when I'm TT ing.

Typical Analytical

Get an indoor trainer with erg and lock yourself into watts. You'll never do outdoor intervals again.

Team4Luke

p929 wrote:

Hi,

Although I'm only 1 year on cycling I decided to buy a dual side powermeter 1 month ago in order to improve my training. Before the purchase, I had read and watch videos about training zones and it seemed as 'easy' to pace the intervals a I used to do with my HR, the only difference would be that the value would have an instantaneous response and not been affected by weather, temperature, as HR is.

However, since I did my FTP test I realized how hard is to keep the power output within a small range when performing intervals. For instance, my Z3 (tempo) should be 160-192W. It's a very narrow 32W band, but every time I'm on the bike I can see how the values jump around all the time below/on/ and above the required zone. Nevertheless, I always to keep the the average power within the training zone, and NP usually agrees with the AP.

I have tried to control power by shifting the best I can trying to accommodate to the terrain. OTOH, I found that I can control better the power when I'm climbing, although far from perfect.

Are there any tips from more experienced guys to pace those intervals correctly. BTW I'm using a 3s average on my Wahoo Elemnt, I think that it'd be more complicated pacing the interval when using 5s or 20s averages on the head unit, but if someone thinks otherwise, I'd love to heard about it.

Below is a pic of my last interval training (sweet-spot) showing some statistics.

Your issue with pacing and maintaining a controlled output in a session is nothing to do with using a HR or PM, this is simply you are not aerobically fit at the top end of this zone and don't do and have got enough of this type of training banked - "1 year into cycling" as opposed to 1 years training.
You are also incorrect with your assumption about Hr being affected by weather temperature etc - it is not-it is your body's ability to perform or not perform when it is influenced by external factors like weather, illness etc.
So back to basics here, if it very cold you might find it very hard to get to your HR threshold this does not mean you can easily look at another device ie a PM and just keep up your normal 300watts for an hour in the cold, it is all about how you physically feel when training not what numbers are in front of you.
Another example that people wrongly blither on about is cafeine affects HR but not power- again wrong, it affects your body's ability to perform, so yes you might see a noticeable rise in HR (but why would you down a few coffees before riding !) thus you might feel a bit hyper and output a few extra watts leaving you thinking your power is up when in terms of a training gain you have been mislead.
Understand you body and HR is a great tool see how it responds or not to training loads and tiredness, once you are doing the correct upper level training for at least one hour your ability to conserve your energy and strength will come on and you will output much more smoothly HR or Watts - all about controlled training.

Alex_Simmons/RST

Team4Luke wrote:

Your issue with pacing and maintaining a controlled output in a session is nothing to do with using a HR or PM, this is simply you are not aerobically fit at the top end of this zone and don't do and have got enough of this type of training banked - "1 year into cycling" as opposed to 1 years training.
You are also incorrect with your assumption about Hr being affected by weather temperature etc - it is not-it is your body's ability to perform or not perform when it is influenced by external factors like weather, illness etc.
So back to basics here, if it very cold you might find it very hard to get to your HR threshold this does not mean you can easily look at another device ie a PM and just keep up your normal 300watts for an hour in the cold, it is all about how you physically feel when training not what numbers are in front of you.
Another example that people wrongly blither on about is cafeine affects HR but not power- again wrong, it affects your body's ability to perform, so yes you might see a noticeable rise in HR (but why would you down a few coffees before riding !) thus you might feel a bit hyper and output a few extra watts leaving you thinking your power is up when in terms of a training gain you have been mislead.
Understand you body and HR is a great tool see how it responds or not to training loads and tiredness, once you are doing the correct upper level training for at least one hour your ability to conserve your energy and strength will come on and you will output much more smoothly HR or Watts - all about controlled training.

I'm not sure much of that makes any sense.

Suggesting external factors such as environmental conditions, illness etc do not impact HR response, only one's performance capacity is patently false.


For the OP - as others have said already and in various ways, don't get overly hung up with the momentary variability in power output - power output on a bicycle is naturally stochastic, especially when riding outdoors, and in some instances there can be some artificial technological variability in the reported power data as well depending on the power meter and head unit.

The various metabolic responses (HR, blood lactate level, hormone levels etc) don't change instantly with changes in intensity (power demand) but rather follow a predictable time course and mostly have half lives in the order of about a minute, so being concerned with short term variations in power is unwarranted - hence why looking at average power is most useful for shorter duration efforts (anything less than say 20-min) and both average and normalized power are useful for longer duration efforts.

Indeed there is no significant metabolic difference to performing a steady state effort at 200W to one where the power varies between 0W and 400W with rapid frequency (e.g. with a micro interval period of around 15 seconds or less). The metabolic responses will be the same.

If doing intervals is something you feel you need to do (and it may not be considering you are relatively new to cycling) then what is important is that the entire effort(s) is(are) performed at about the right level overall.

For those newer to using power measurement as a guide to intensity of effort while riding intervals, there can be a temptation to make many rapid and short term changes to effort in response to the numbers on the computer. Don't. This is "chasing your power tail".

Just keep the overall effort level consistent and you'll likely find that the numbers will come back into line. If not and you find that over the course of 15-30 seconds it's clear you are consistently above or below your desired range then you can make a subtle change in effort and monitor for the next 15-30 seconds. It often doesn't require much of a change in effort. It may take a couple years of consistent training to acquire a greater level of control over your rate of perceived exertion and how that relates to your power output.

Use of some smoothing of the displayed power data can assist with this, especially if you are not someone who can naturally integrate the data.

And most importantly, don't stare at the meter's computer screen for long periods, just use occasional glances to gain a bit of a sense as to how the power relates to how you feel - you need to be watching where you are going!