Training with heart rate vs training with power | Which is best for you?

Is heart rate training still have a place or are power meters now essential to success?

Russell Burton / Our Media

Published: October 3, 2023 at 3:00 pm

Training with data is more popular and accessible than ever. Using a heart rate monitor or power meter allows riders to track training sessions, analyse fitness improvements and pace efforts.

But what are the pros and cons of training with heart rate versus training with power, and what’s the best option for you?

A heart rate monitor is one of the most widely used training tools in cycling because of its simplicity, ease of use and low cost, offering riders an affordable route into training with data.

However, with power meters becoming cheaper than ever and an increasingly common sight aboard the bikes of non-professional cyclists – not to mention the integration of power meters into smart trainers – it’s logical to ask whether it’s better to train with a heart rate monitor or a power meter.

After all, it’s not always clear exactly what a power meter offers that a heart rate monitor doesn’t, or whether you should abandon heart rate training entirely if you decide to upgrade to a power meter.

To get some answers, let’s take a look into how each tool works, their respective pros and cons, as well as some tips on combining the two for the best training results.

How heart rate monitors and power meters work

Jack Evans fitting heart rate monitor during lab trial
Heart rate straps loop around your chest and measure electrical signals from your heart. - Chris Teagles

Most heart rate monitors work by measuring the electrical signals generated by your heart as it beats. A simple chest strap sends that signal to a connected device like a bike computer or smartwatch.

Some wristwatch heart rate monitors use a different method, which involves shining light into the skin and optically measuring the amount of light reflected back, which is affected by the blood flow within the arteries. This measurement is taken at the wrist and therefore doesn’t require a chest strap.

Heart rate straps are generally considered to be more accurate than wrist-based heart rate monitors.

4iii Precision Pro dual-sided power-meter
Power meters are usually found in the cranks, spider or pedals. - Scott Windsor / Our Media

In comparison, a power meter is a component on the bike itself (e.g. spider, pedals, cranks etc), or on a smart trainer, with a number of strain gauges, which measure the force applied when pedalling.

Using measurements of both the torque applied and angular velocity (or cadence), it’s possible to then calculate power output (measured in watts).

It’s quite clear, then, that although both tools are used for similar purposes — that is, to provide data to guide your training and racing — they’re actually measuring two very different things.

Why train using a heart rate monitor?

OBSERVATORIO ASTROFÍSICO DE JAVALAMBRE, SPAIN - AUGUST 31: (L-R) Romain Bardet of France and Team DSM - Firmenich and Lenny Martinez of France and Team Groupama - FDJ - White Best Young Rider Jersey compete in the chase group during the 78th Tour of Spain 2023, Stage 6 a 183.1km stage from La Vall d'Uixó to Observatorio Astrofísico de Javalambre 1947m / #UCIWT / on August 31, 2023 in Observatorio Astrofísico de Javalambre - Pico del Buitre, Spain
The humble heart rate monitor is useful for all levels of cyclist. - Tim de Waele/Getty Images

Starting with a heart rate monitor, its greatest strength is cost-effectiveness.

A reliable heart rate monitor can be picked up for less than £100, and if you already have an existing head unit from the likes of Garmin, Wahoo, Polar, a compatible chest strap may be all that’s needed.

Using a heart rate monitor is very straightforward — another string to its bow.

Pairing your chest strap with a head unit, or recording with your smartwatch, is quick and simple.

Garmin Fenix 6 Pro Solar GPS smartwatch
Heart rate monitors are simple to connect to watches and computers. - Alex Evans / Immediate Media

By performing some very basic testing, you can quickly establish the training zones you need to work within to provide some structure to your training.

Heart rate monitors work well in situations where the riding intensity is kept relatively stable, such as longer, base training rides while working on your cycling endurance.

In addition, they can be very useful in recovery workouts to ensure your effort level is kept low enough to not induce any further fatigue.

Where heart rate training is limited, however, is in the lag associated with the heart’s response to changes in exercise intensity. Many external factors can affect that response.

Ridley Falcn RS Ultegra Di2 road bike
Heart rate is an ineffective way to measure surges in effort. - Russell Burton / Our Media

When riding in a very stochastic or punchy way, the heart rate response lags behind these sudden changes in effort.

Therefore, it can’t provide reliable real-time feedback of how hard you’re pushing on the pedals. Practically speaking, this makes pacing short high-intensity intervals very difficult.

Nor can a heart rate monitor tell you exactly how hard you’re riding during these short efforts, as your heart is playing catch-up.

COURCHEVEL, FRANCE - JULY 19: White jersey of best young rider Tadej Pogacar of Slovenia and UAE Team Emirates crosses the finish line of stage seventeen of the 110th Tour de France 2023, a 165.7km stage from Saint-Gervais Montblanc to Courchevel / #UCIWT / on July 19, 2023 in Courchevel, France.
Underscoring heart rate's limitations, Tadej Pogačar often races without a chest strap. - Jean Catuffe/Getty Images

What’s more, factors like your hydration level, air temperature, the amount of sleep you’ve had, levels of caffeine in your system and altitude can significantly change the heart rate at a given intensity.

This further undermines the reliability and consistency of the data you’ll use to train with and analyse after your ride.

Pros and cons of training with heart rate

Pros

  • Affordable
  • Easy to use
  • Easy to understand basic data & establish training zones
  • Good for pacing long efforts
  • Can be an indicator of fatigue, illness or overtraining

Cons

  • Susceptible to heart-rate lag
  • Can be affected by a wide range of external factors

Why train with a power meter?

Garmin Rally XC200 power meter pedals
Power meters capture your output in watts not your body's response to a given effort. - Felix Smith / Our Media

Unlike heart rate data, which represents your body's response (and delayed) to your input on the pedals, a power meter is a real-time measure of your output, i.e. what your effort is actually amounting to in the real world.

The key benefits of training with a power meter are the instantaneous feedback it provides and the lack of external influences that would otherwise undermine the data.

A power meter also allows for the objective measurement of fitness progression over time, such as improvements in your Functional Threshold Power.

Most power meters sample the forces applied during pedalling many times per second, giving very quick feedback that’s extremely useful when it comes to pacing both longer and shorter efforts.

The precision and real-time feedback of a power meter also allows you to target specific training adaptations easier than with a heart rate monitor.

Stages Dura-Ace G3 power meter
Power meters are significantly more expensive than heart rate monitors, but offer a wealth of training data. - Russell Burton

The best power meters can even relay each leg’s contribution to the power production, which can help indicate any left-right imbalances.

In addition, performing either basic field testing or using a power meter in combination with lactate and/or VO2 max measurements in a lab, it’s possible to gain a wealth of understanding on where your individual strengths and weaknesses are.

Lab assistant taking blood lactate sample of male cyclist
Measuring power, heart rate and blood lactate is informative but unfeasible for most riders. - Chris Teagles

This will help you decide what to focus on improving in training and which cycling discipline may suit you the best.

The accuracy of power also demonstrates the benefit of the latest smart turbo trainers, which can automatically control the resistance to ensure you’re hitting the exact power numbers required to get the greatest benefit out of your session.

The drawbacks of power meters are mostly centred around their cost and the greater understanding they require.

You need to know how to train with power to get the most out of them during sessions and when performing your post-ride analysis.

SRM power meter
Do you know your watts from your BPM? - Simon Wilkinson/SWPix.com

Wattage jumps around a lot more than heart rate when riding, and this can take some getting used to, particularly if you are tasked with riding to a specific wattage for a training session.

Some power meters also need to be calibrated on a regular basis to ensure the wattages are accurate, although this is normally a simple task.

The wealth of metrics available in cycling apps like TrainingPeaks, Golden Cheetah and WKO also mean that it’s not immediately obvious what the data is telling you and what you should do with it right away.

Wahoo Kickr V6 side view
Power meters are integrated into smart trainers which can also connect to heart rate monitors. - Simon von Bromley / Our Media

With a bit of reading or by working with a knowledgeable cycling coach, many of these so-called weaknesses become less and less of a problem and the data turns into an asset you can use to improve your fitness and performance.

The rise of indoor cycling apps has also made training with power more accessible than ever. The likes of Zwift, Wahoo RGT and Rouvy use your wattage (or an estimate of it, if you're not using a smart trainer) to help calculate your in-app speed and power your avatar as a result.

The workouts and training plans offered on most apps used power-based training zones, providing a helping hand to target specific areas of fitness.

Pros and cons of training with power

Pros

  • Accurate, real-time reflection of output
  • Can target specific training zones & adaptations
  • Huge range of data
  • Easier to track fitness progression
  • Power training now an option through smart trainers and apps

Cons

  • More expensive (but an increasing number of affordable options)
  • Amount of data can be overwhelming
  • Some power meters require calibration

How to train with heart rate and power together

Screenshot of Training Peaks ride file
Track heart rate and power because their relationship can be insightful. - Training Peaks

The best way to get the most value from heart rate and power-based training is to use both simultaneously. You’ll then have an input and an output measure to work with.

Not only will that give you wattage data to track improvements in power, but it will also give you heart rate data to better understand your body’s response to training.

By understanding and monitoring the relationship between the two, you’ll be able to draw far better conclusions from your data and make more informed decisions about how to create a training plan going forward.

So, what will training with both power and heart rate data allow you to do? Here are a few of the most useful ways to use the two tools together.

Testing and setting zones

Jack Evans' pained expression during sodium bicarbonate lab trial
Average power and heart rate from maximal efforts is used to set training zones. - Chris Teagles

By performing a simple maximum heart rate or functional threshold heart rate test, as well as using power profile or Critical Power testing protocols, you’re able to set benchmarks for comparison against later down the line.

You can also establish your training intensity zones for each respective tool.

These heart rate and power intensity zones don’t need to line up perfectly, since each is measuring a different thing. What’s most important is to know how the two relate to each other for you as an individual.

Monitoring fitness progression

Screenshot of Training Peaks HR and power graph
On long rides, ideally heart rate (in red) shouldn't drift upwards if power (in pink) remains steady. - Training Peaks

There are numerous ways that having both heart rate and power data at your disposal can help you assess how well your fitness is progressing, and whether your training plan is producing the desired results.

One such way is by looking at the ‘rate of decoupling’ within a workout. This is a measure of how much divergence there is between your heart rate and power during the course of a steady ride.

If heart rate goes up for a steady power output, we can say that some ‘level decoupling’ has occurred, meaning your efficiency has reduced over the course of the ride.

While this could be related to a number of the influencing factors mentioned earlier, it can help you to understand how aerobically fit you are and whether your endurance is sufficient for the duration and demands of what you’re preparing for.

Of course, it’s still possible to assess fitness progression if you only have access to either heart rate or power data.

Merida Scultura Limited Road bike
Timing yourself on a familiar stretch of road is another method of testing fitness. - Russell Burton / Our Media

Where only heart rate data is available, try riding a real-world or virtual segment such as a climb at a steady heart rate and see if your time for the segment improves.

Just ensure the conditions and other factors are kept as similar as possible as you perform repeat tests.

With power, you can repeat the power profile test or FTP test (you can also complete an FTP test on Zwift) to get a good gauge on whether you’re seeing improvements in the right areas of your fitness, by comparing the results to the original benchmark testing.

Knowing your limits

Amazfit GTR 4 smartwatch
Atypical heart rate readings can be a sign of fatigue. - James Costley-White / Our Media

Is overtraining still possible when using heart rate and power together?

The short answer is yes, but if you build up an understanding of your data over time, and pay attention to the numbers, it can easily be avoided.

By training with both heart rate and power data together in most of your workouts, you’ll very quickly establish a picture of a normal heart rate to see for a given power output, or vice versa.

When you see the relationship between these numbers change dramatically, you can make decisions about what may have caused it and whether the change is a positive or a negative one.

Having an awareness of your limits can also help you pace efforts, both within training sessions and in competition.

Power is ideal as a pacing tool with its instant feedback, but you can also pace yourself during steadier hard efforts like a time trial or longer road or MTB race with heart rate.

Sheet showing RPE scores from 1 to 20
Although subjective, your own rating of perceived exertion is a valuable metric. - Chris Teagles

Use your own rating of perceived exertion in combination with the heart rate data, to help judge shorter efforts where heart rate data alone is less reliable.

You can combine this with your knowledge of previous training sessions and races to inform how hard to push and for how long.

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