What are the benefits of cycling Power Meters?
With the costs of purchasing or renting a power meter reduced and access to indoor training on smart turbos (which have power on them), more and more athletes have an idea of their power when riding a bike. At this point, for those who haven’t yet made the step to training with power, the question has to be asked: if it is more accessible, is it worth using one? And what can you learn from using one in training and racing?
What does a power meter provide us?
A power meter provides a measurement of the effort that someone is exerting. Another way of looking at it is that power measures an athlete's work capacity for a set time. It is something that can be measured for an individual and is measured in Watts, W (e.g. you can sustain 200W for 5 minutes) or normalised for an athlete’s weight (W/Kg) or aerodynamic drag (W/m^2). In scientific terms, it is how much energy someone exerts every second.
Most power meters measure how much force is applied as an input (at the pedals, the crank or the hub) and how fast that force is applied. This means we can measure average effective pedal force and cadence, which gives us two additional metrics. This means that a Watt can be created differently. You can create that 200W for 5 minutes at a low cadence (high force on the pedals) or a high cadence (low force on the pedals).
Immediately, we can start to see if someone is grinding the pedals or spinning. Both methods have advantages, and a lot comes down to individual preference. Nevertheless, it can give us insight into how someone rides and may offer helpful points around improving effort or pacing without “real” training. Perhaps you can sustain a higher cadence for longer (utilising your cardiovascular system more), or perhaps you have excellent muscle endurance and prefer a higher-force approach.
Why does tracking power help us understand performance improvements?
Tracking power enables athletes a method to measure training progress. You can’t easily use heart rate, Rate of Perceived Exertion (RPE), or speed to check improvement. Athletes have limited control over metrics like RPE or heart rate. Athletes can go easier to see their heart rate fall or push more to see it rise. However, as a session progresses, the RPE for the same speed will increase, or if an athlete keeps the intensity the same on an RPE scale, speed could drop. Think of almost any race you did: that pace you found all too easy at the beginning suddenly seems like a world record pace and is impossible to hold on to at the end. Additionally, high speed doesn’t always mean high effort – anyone who has ridden up and down a hill will testify that the opposite is often true! You can use two of the metrics to measure improvement crudely: As a season progresses, an athlete's speed for a given heart rate or RPE value should improve.
If you start doing testing on your bike and you want to see how your performance has changed. This can be done on known courses. For example, you could use the same 10-mile time trial route and see your speed improve as you get faster. However, speed is often impacted by the conditions as well. The air pressure, the air resistance, and the wind all impact the speed that you go on. So will the temperature and other factors around rolling resistance and the efficiency of your bike. This means you could go faster if you were to clean your bike and have a different tyre pressure from the last time you raced the course. It is not a reliable or accurate representation of your performance changes.
Power, on the other hand, is an input metric. If you push harder on the pedals, your power will increase; if you ease up, your power will decrease. The readings are instantaneous, unlike your heart rate, which will also rise and fall. Sometimes, when athletes start using a power meter, they don’t realise why they find hills so hard. When you look at the delay between how hard someone pushes at the bottom third or half of the climb and a corresponding heart rate, you’ll see that the heart rate doesn’t get anywhere near its maximum until halfway up or even after the hill. On the other hand, their power spike will be clear at the bottom of the climb. To put it another way, there is a time lag between what the actual intensity is (power), the physiological impact (heart rate) and how it feels (RPE), all while speed has decreased. This means athletes work harder without realising unless they have power as a metric.
Prescribing accurate training doses using training zones
It is challenging to prescribe training to people using speed, RPE or heart rate. RPE is subjective and changes over time, whereas heart rate can be delayed and often changes day to day; speed can be affected by external factors like gradients, wind or road surface. Furthermore, athletes who are newer to cycling will struggle to match any metric to their physiological profile, if they even know what that is and will struggle even more if the terrain or conditions are varied. Most newer cyclists' ability to pace themselves is what lets them down. They haven’t managed to monitor effectively how their body responds to effort or translate that into effective pacing. Many just know how to “stop” or “go” but haven’t even found the “hard” or “easy” gears! Therefore, any prescribed training would be inaccurate and often not repeatable.
We know that power is a useful metric because it is instantaneous. It is also comparable between different athletes and between sessions or seasons, allowing us to track improvements and changes to an athlete’s performance. Initially, most people use functional threshold power (FTP) and well-researched training zones to set training sessions. These can be sense-checked by triangulating effort (RPE) and heart rate for an athlete to know if they are feeling good or bad on any given day. (If a target power feels harder than it should, perhaps you haven’t recovered properly).
Beyond that, you can also get quite “geeky” by individualising your power profile, which can further individualise the training zones. This has further positive implications for racing or training using the power meter.
Training with a power meter
When using a power meter in training, we can ensure that the training dose is very accurate and training sessions are subsequently executed at the prescribed intensity and effort. This can be set based on the individuals' physiology instead of RPE and can also be tracked. This ensures that training progressions are highlighted. Otherwise, when you do your 10-mile test to see how you have improved, if you had got faster and your power had reduced, you don’t see that as an improvement in training (unless you’ll be working on improving your aerodynamics).
On the other hand, if your power has increased, regardless of the time taken, you have improved your work capacity, and your training has improved.
When training to power, we can also ensure that the power is constant regardless of what the terrain or the weather is doing. This provides an effective training dose. In other words, the power will not be consistent with changing speeds. You can do the same power going up and down hills, ensuring your effort is consistent throughout the climb and back down again (if you don’t freewheel). This enables a better training effect. It also means you are less likely to accidentally drift through different training zones or spikes when riding variable conditions or terrain and slip into the “dreaded” grey zone of training, where you work outside a desired training zone.
Finally, training using a power meter allows further detail into how someone is training. Power meters often will enable us to see how hard someone presses the pedals and how fast they move them around. This can become another layer of information that can help athletes make good decisions on training performance. For example, if someone completes a three-minute intensive effort and cadence and power remain consistent for the full three minutes, they have executed the interval well. Perhaps, though, the cadence dropped, it would suggest that the athlete hasn’t quite got the fitness for that intensity power for the full three minutes.
When used in conjunction with heart rate, you can start to spot additional training points. It may be that the third block of effort seemed much more challenging to sustain than the first two in a training session. On the surface, this may not make sense, but when you look at the heart rate changes, it may be the recoveries between the efforts weren’t quite long enough, and your body is still recovering from the first one or two intervals.
In summary, power meters can provide much more insight into how you train, generate speed and where you want to focus next to improve for your next race.
Power meters when racing
When it comes to racing, power meters are even more effective. You would have learned what power you can sustain for particular durations through training. Then, when you start your event, you just ride at the power you know you can maintain and do not deviate from it. This enables accurate and even pacing and ensures athletes do not go too hard at the beginning and then fade; this is particularly true in time trials or triathlons, where consistent output is the most effective for your speed.
Additionally, you can make tactical decisions in races when you understand your power profile. Perhaps you identify that you have a strength in working over 5 minutes, but not 30s. Instead of waiting until the sprint at the end of the race, you may choose to push hard with 5 minutes to go, knowing that you are more likely to win.
Power metres are sometimes referred to as a way of cheating in a race because they provide you with such essential information. Once athletes begin using power metres when training, they often can’t see how to ride without it.
It’s important to remember that the athlete with the most power is not always the athlete who wins. The key is to use your power to be more efficient in your training, more accurate in your execution and enable the fastest speed you can to cross the finish line first or set yourself up for the best run you can.
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