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Defining and measuring intensity on the turbo

Or if you're already convinced then read on to find out how to get the most out of it.

Defining and measuring intensity

You’ll get far more out of your workouts by training at set intensities, established with regular testing. Here’s some different ways to measure what you’re doing (in order of ‘sophistication’ and cost).

1) Feel or perceived effort (RPE, or rate of perceived effort) – the most important metric but the hardest to calibrate. If I say ride at 5/10 effort for an hour you’re likely to put out far more power at the beginning when you’re fresh, than at the end when you’re tired. So if the whole session is at 5/10 effort, it should feel more like 4/10 effort at the beginning, and 6/10 by the end.

Even if you’re training by power or HR, you should still pay attention to RPE, both to check that your zones are set right, and so that you become aware of what it feels like, so that you’re able to ride in feel rather than being tied to watch screen, especially if you don’t have access to these other metrics when riding outside.

2) Cadence – cadence isn’t a measure of intensity, it’s how fast your legs are moving (in RPM, revolutions per minute). But power (how we measure intensity) is a product of torque (in simple terms, what gear you’re in or resistance is applied by the trainer) x cadence, so if you stay in the same gear/ resistance and increase leg speed then you’re working harder. If you don’t have any other metrics available then a cadence sensor is pretty cheap and it’s a good proxy for effort, and many sensor and training apps such as Zwift can then calculate that ‘virtual’ power.

Cadence is also important because we can limit risk by staying within a safe cadence range (from about 60rpm – 100 rpm, depending on the person and experience) and can work on developing our technical skill by cycling at different cadences.

3) Heart rate – Another key metric, this shows how hard your body is finding the effort, in the same way as RPE changes for the same power effort (rather than how hard you’re working), which is both an advantage and disadvantage. A disadvantage because the most efficient way to train is to keep constant power (not effort) and because it be affected by things like caffeine, sleep or stress and most significantly fatigue, so you’ll get a different reading for the same power. An advantage because it can warn you is things are off course (if your heart rate is higher than normal for the same effort, then it’s an indication something might be wrong, for example you’re getting ill or are over tired or stressed, and need to adjust your training). It’s also an advantage because a heart rate monitor (HRM) is loooot cheaper than a power meter so even for those with a smart trainer, might judge effort when outside with a HRM. Bear in mind, if training by HR a strap is usually more accurate than a watch.

4) Power – the gold standard (ish). This measures the actual power and therefore doesn’t change as you get more tired. This means you’ll go easier at the beginning of an interval so that you can finish it strong, rather than tiring half-way through. Given it’s much more precise you can follow more structured intervals which can keep the training more engaging, and builds accountability. However you need to check that power meters are calibrated (check manufacturers instructions) and be aware two metres may give very different readings so don’t rely on a turbo reading to set your power out on the road. If you thinking about buying a turbo or currently have a standard/ non smart trainer, and are thinking of investing in power, personally I would get a power metre for my bike, rather than a smart trainer, so that you can also use it outside.

Setting your training zones

Of course you can just get on your bike and ride, but to get the benefits of the turbo you'r best doing structured training which will take you through a variety of training zones.

Based on feel:

Based on Heart Rate

You can either set up heart rate zones based on Max Heart Rate (MHR) or Lactate Threshold Heart Rate (LTHR). If you have a watch or bike computer you should be able to set the zones up on there (on a Garmin, go to Garmin Connect/ Garmin Devices/ select the device/ User Settings).

If using MHR check your training data for the last 6 months rather than using an equation to calculate (cos they’re usually wrong), although of course that relies on having done max effort training.

To calculate LTHR see below and then look up your training zones here

Based on power

In order to accurately set your power zones for training you need to do Functional Threshold Power (FTP) test. This is an estimate of the maximum sustainable power that you can hold on a bike for an hour.

After warming up, you can either do a ramp test if your turbo has one set up, or ride as hard as you can, at a sustainable power, for 20 mins. For LTHR it must be the 20 min test. Your FTP is 95% of your average power for the 20 min test.

To do the test:

- This test is hard! Make sure you are well rested and have had sufficient nutrition before doing. Don't do if ill or injured

- If planning to use heart rate as part of measuring your training intensity (e.g. for out on the road) make sure you wear a HR monitor for the test and that it is recording data.

- Dont go out too hard and then find you need to drop, it should be the same power all the way through. Ideally start at a 6/10 effort, and try and hold your power there. By the end of the workout that power should be a 10/10 effort (you’ll still be holding about the same power, it will just feel harder by now). If you get to 10 mins in and that’s still feeling like 6/10 effort then go a bit harder. By the end you should feel absolutely exhausted, like you couldn't have given any more.

- Then look up your training zones here (or my clients, see your Training Plan)

Holding yourself to account

Then you want a way to see your efforts whilst you're training, and ideally recording them if you analyse your training data. So if you have a training watch or bike computer, set it up so that you can see the relevant info.

As well as current power and/or heart rate, I'd suggest you want current or last lap power/HR so that you can check you hold it all the way through (rather than just hitting the numbers when you happen to look) and you might find it more useful to see %FTP or HR training zone, rather than the actual numbers. Here's mine as an example.

(on a watch remember you can usually have more than one screen, so have your core info on one screen and then things such as cadence that you can flick to on another).

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