Training for cyclists: These measurement techniques will help you improve

Anyone who watches races on TV will see all sorts of metrics and product placements for a whole host of sensors. Anyone putting together a training plan will quickly come across data that makes managing their training load easier and more effective. Just have a look around: Power metres from 300 euros, heart rate belts for 50, smartwatches with HRV analysis, cadence sensors for 30 euros – and somewhere you’ll read (perhaps even here on our site) that cyclists these days are best advised to train based on watts. But is that actually true? And what do you really need? That, in turn, depends on what you’re aiming to achieve with your cycling. Measurement technology provides tools. However, the most expensive tool isn’t automatically the right one for everyone who uses it.

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Level 0: Your body awareness – the underrated measuring tool

Before we talk about technology, let’s start with the most important sensor: yourself. In sports science, this is known as RPE – Rating of Perceived Exertion, i.e. the subjective assessment of exertion. The concept was developed by the Swedish physiologist Gunnar Borg and has been used in training science for decades. The adapted scale is simple: from 6 or 1 (no effort at all) to 20 or 10 (maximum exertion). Studies show that RPE correlates remarkably well with physiological markers such as lactate thresholds and VO₂max – so how you feel can actually reflect what’s happening inside your body.

Who would find that enough?

For anyone who cycles two or three times a week to clear their head, stay fit and have fun. If you’re not chasing performance goals, you don’t need a single piece of kit. Just set off, listen to your body and have fun. But: RPE has its limits. On bad days, when you’re stressed or sleep-deprived, your own assessment can be misleading. And if you want to measure your progress, you’ll need numbers at some point.

Level 1: Heart rate – the classic method

For decades, the heart rate monitor was the standard tool for training management – and for many cyclists, it still is. A chest strap (from around 40 euros) or a smartwatch shows your heart rate in real time. The benefits of heart rate monitoring: it shows you just how hard your cardiovascular system is currently being worked. You can define training zones (basic, tempo, threshold) and use them as a guide. Over time, you can track your progress: if your heart rate is lower whilst covering the same distance, you’ve become fitter. Modern watches and apps use heart rate variability (HRV) to calculate your recovery status.

The restrictions

It reacts with a delay. When you start climbing a hill, your watts shoot up immediately – but it takes 30 to 60 seconds for your heart rate to catch up. This is a problem for interval training. It depends on how you’re feeling on the day. Caffeine, sleep, stress, heat, dehydration – all these factors influence your heart rate without affecting your actual performance. It doesn’t measure what you’re achieving, but how your body reacts to it. That’s a fundamental difference.

And as we’ve already learnt in the newsletter: your heart rate can shoot up dramatically with your cadence. “That can throw your training off, because we do vary our cadence whilst training,” says Andrea.

Who would find this useful?

For anyone who wants to train in a more structured way without spending a fortune straight away. If you cycle three to four times a week and want to distinguish between base training and high-intensity sessions, a good chest strap and an app such as Strava or Polar Flow will serve you well. Important: Chest straps provide significantly more accurate measurements than optical sensors on the wrist. Wrist-based watches often give unreliable readings, particularly during interval training or in cold temperatures.

Stage 2: Speed and cadence – useful, but limited

Many cycle computers display speed and cadence. Both are useful pieces of information, but they are of limited use for training management. Speed is affected by wind, gradient, surface and tyre pressure. You can put in a higher effort at 25 km/h into a headwind than at 35 km/h with a tailwind. As a training parameter, speed is therefore virtually useless. Cadence, on the other hand, is an underrated aid – especially for beginners. If you ride consistently at 60 revolutions per minute, you put more strain on your knees and joints than if you pedal at 80 to 90 revolutions. A simple cadence sensor (from around 25 euros) can provide valuable guidance here. If you want to protect your knees on a multi-day tour, you should cycle in lighter gears at a higher cadence.

Stage 3: The power metre – the be-all and end-all?

Now we’re getting technical. A power metre measures the mechanical power you’re applying to the pedals – in watts, in real time, with no delay. That’s the key difference compared to heart rate: watts are objective. 200 watts is 200 watts, regardless of whether you’re tired, have had a coffee or it’s 35 degrees. Our engineer and trainer Andrea explains the measurement principle as follows: the force we apply to the pedal causes the system to deform on a microscopic scale – imperceptible, invisible, but measurable.

So-called strain gauges detect these minute deformations. The power metre then calculates the power output based on the deformation, the cadence and the material constants of the components. There are three types:

Crank-based systems

The measurement is taken at the crank spider. Andrea is clear on this point: “In my comparative tests, crank-based systems demonstrated the highest levels of accuracy. SRM lives up to its premium standard – remaining highly accurate even with older cranks.” The reason: the electronics are housed in a protected enclosure, there is more space for redundant sensing units, and the measurement point is less susceptible to external influences.

Crank arm systems

Here, the sensor is located in the left (or right) crank arm. Advantage: inexpensive and easy to retrofit. Disadvantage: many of these systems only measure on one side and double the reading. “This approach only works if the rider has a 50/50 right/left balance,” warns Andrea. “It’s more theory than practice.” Anyone who rides just one bike and looks at the values relative to themselves can live with it. For absolute comparisons or when switching between bikes, it’s problematic.

Pedal systems

It’s practical because you can switch between bikes quickly. But Andrea, as an engineer, raises valid concerns: the pedals are exposed – in the event of a fall or the bike tipping over, they’re the first thing to hit the ground. Furthermore, the depth to which the pedal is screwed in affects the measurement: “Even if it’s screwed in just a little tighter or looser, it can cause a measurement error.” Her motto: “Better not to measure at all than to measure incorrectly.”

Accuracy can be deceptive

What many people don’t realise: ‘calibration’ is not the same as ‘verification’. Andrea Jeschke clears up a common misconception: ‘Internal system calibration does not guarantee measurement accuracy.’ What the cycle computer refers to as ‘calibration’ is, in reality, a zero-point adjustment – it ensures that zero is displayed when there is no load. Whether the measurement is correct beyond that is not checked. For that, a professional calibration against a known reference would be required – and very few manufacturers offer this.

Who would find this useful?

For anyone looking to specifically improve their performance – whether it’s for an Alpine marathon, a time trial series or simply to get the most out of limited training time. But your riding position makes a bigger difference to efficiency than the third decimal place in your wattage reading.

Stage 4: The combination – the overall picture

The smartest approach to training management does not rely on a single tool, but combines several data sources. In sports science, these are referred to as ‘internal load’ (how the body reacts: heart rate, RPE) and ‘external load’ (what is actually being produced: watts). Both provide different information. If your heart rate is suddenly significantly higher than usual whilst maintaining the same power output, this may indicate overtraining, dehydration or the onset of an illness – information that a power metre alone does not provide.

Practical advice for your cycling life

Your body’s feedback isn’t just a stopgap; it’s a scientifically recognised measuring tool. If you cycle twice a week, you don’t need a power metre.

A heart rate monitor is the best investment for under 100 euros. It shows you whether you’re pacing yourself – and whether you’re getting fitter.

A power metre is worth it if you’re specifically working on your power output. For everyone else, it’s a nice bit of kit, but not essential.

According to our expert, crank-based systems are not only the most accurate – they are also often cheaper second-hand than new pedal systems.

The best setup is the one you actually use. A heart rate monitor that you’re wearing is more useful than a power metre with a flat battery.