If you want to use a heart rate monitor or power meter for training, but don’t know how, you’re not alone. Unfortunately, the simple act of owning either device will not make you faster. To make fitness gains, you’ll have to make sense of the numbers.
This article will explain how using heart rate and power can improve your training. If you need a basic understanding of what heart rate and power are, read: What Are Heart Rate And Power?
It’s All About Your Threshold
To determine your current level of fitness, you can conduct a threshold test. There are many ways to perform a threshold test. These range from a lab-based blood lactate study to a do-it-yourself time trial.
A threshold test will give you the theoretical maximum heart rate or power value you can sustain for an all-out 1-hour effort. You can then build a table of training zones using your threshold value.
Each training zone consists of a range of heart rate or power values. You then calculate the values for each zone using a percentage of your threshold value.
Different zones produce different physiological adaptations. For example, training in Zone 2—the endurance zone—will primarily help athletes improve their endurance fitness.
Scientists debate about the correct number of zones, but that is beyond the scope of this article. What is important to understand is using any system of zones can improve your fitness. Here is an example of the popular seven zone system developed by Dr. Andrew Coggan.
| Zone | % of Threshold Power | % of Threshold Heart Rate |
|---|---|---|
| 1 – Active Recovery | < 55% | < 68% |
| 2 – Endurance | 56-75% | 69-83% |
| 3 – Tempo | 76-90% | 84-94% |
| 4 – Lactate Threshold | 91-105% | 95-105% |
| 5 – VO2 Max | 106-120% | > 106% |
| 6 – Anaerobic Capacity | 121-150% | N/A |
| 7 – Neuromuscular Power | N/A | N/A |
Comparing Heart Rate And Power
Power is not affected by your level of hydration, stress, or fatigue. It’s also not affected by environmental conditions like elevation or heat. The force required to generate 300 watts will always be the same. Just like the strength needed to squat 120 pounds on Monday, will be the same on Tuesday.
On the contrary, many things influence heart rate. Here is an example.
On Monday, you are well rested, the weather is cool, and you are at sea level. Your bike workout asks you to hold 300 watts for 10-minutes. During that 10-minute effort, your average heart rate is 158 beats per minute.
On Friday, you have to do the same workout, but the setting has changed. You had a big presentation due at work, making you stressed and tired after three 12-hour days. On top of that, you are in Denver, Colorado for the weekend. The elevation is 5,280 feet above sea level, and it’s 95 degrees outside.
Do you think your heart rate will be the same during the 10-minute effort? Not a chance. At elevation, your body has access to less oxygen. As a result, your respiratory rate and heart rate increase. Additionally, your body will work harder to cool itself in 95-degree weather. Throw the fatigue and stress from a long work week into the mix, and you have a recipe for disaster. In fact, you may not be able to complete the 10-minute effort.
Should You Use Heart Rate Or Power?
The decision to use heart rate or power is a highly debated topic. Heart rate purists believe you should always listen to your body. Power enthusiasts often choose to ignore the body’s response to external influences. I and many others think both technologies have their place. Here are some examples of where both technologies shine.
Heart Rate
Your body produces energy in more than one way. I’ll simplify this to limit the level of detail. Aerobic energy is created using oxygen, while anaerobic energy uses no oxygen. Your body can produce aerobic energy for a long time and anaerobic energy for a short period.
Activities like long distance running or cycling rely heavily on aerobic energy. Maximum force activities like sprinting use anaerobic energy.
As you increase the intensity of exercise, your body uses different energy systems. Here’s a look at Andrew Coggan’s seven zone system detailing the energy systems used in each zone.
| Zone | Energy System |
|---|---|
| 1 – Active Recovery | Aerobic |
| 2 – Endurance | Aerobic |
| 3 – Tempo | Mainly Aerobic |
| 4 – Lactate Threshold | Aerobic + Anaerobic |
| 5 – VO2 Max | Aerobic + Anaerobic |
| 6 – Anaerobic Capacity | Mainly Anaerobic |
| 7 – Neuromuscular Power | Anaerobic |
Your heart rate is closely related to your energy system breakpoints. Your body switches from using aerobic energy to a mixture of aerobic and anaerobic energy at a specific heart rate. Knowing where your breakpoints occur can be very useful when training. For example, to keep a workout aerobic, stay below your aerobic – aerobic + anaerobic break point.
Heart rate is often better for long steady state aerobic or recovery workouts. The best part is, you won’t have to worry about elevation, temperature, or your level of fatigue. Just monitor your heart rate to make sure you are on track.
I often recommend using power for races, but there are situations where heart rate can be useful. Racing at elevation is a great example.
Producing race-pace power at sea level is easier than when at high altitude. The lack of oxygen at elevation will cause your heart rate to rise. A large enough rise will force your body to use a different energy system. If your race is longer than the amount of time you can last in the new energy system, you’ll blow up before you reach the finish line.
Knowing your race pace heart rate can save you when elevation or temperature sneak up on you.
Power
One of the downsides of heart rate is how long it takes to respond to changes in intensity. I’ll use the following interval set to explain my point.
10 sets of: 1 minute Zone 5 / 1 minute Zone 2
Let’s assume you have a threshold heart rate of 170 beats per minute. Before the set begins, you are warming up in zone 2 and have a heart rate of 130 beats per minute.
To work in zone 5, your heart rate must be greater than 180 beats per minute. The problem is, your heart doesn’t immediately jump to 180 beats per minute as soon as you begin to pedal harder. It can take your heart rate 30 seconds or more to catch up to the effort.
Additionally, while your heart rate is catching up, you have no idea how hard you are working. If your heart rate only reaches 170 when it does catch up, you just wasted the interval.
For this reason, power is much better for high-intensity efforts. The power value on your bike computer will change the instant you apply more pressure to the pedals. This immediate feedback lets you accurately pace hard efforts.
Also keep in mind, high-intensity efforts are typically designed to work your anaerobic system. The goal when working your anaerobic system is to ensure you go hard enough to tap into it. Your resultant heart rate is not that important. A power meter is a great way to know in an instant if you are going hard enough.
When it comes to racing, a power meter is one of the best tools you can have for pacing. It also helps long distance athletes calculate their caloric needs.
If you are nervous before a race, chances are your heart rate will be elevated. In some cases, your pre-race heart rate might be above your race-pace heart rate. When this happens, a power meter will help you pace your race until your nerves calm.
Other Considerations
Power meters are more expensive than heart rate monitors. For the cost-conscious athlete, a heart rate monitor may be the best choice. Recently power meters have become more affordable making them accessible to most cyclists. Regardless of the technology you choose, make sure you select a reputable device.
The important thing to remember is, owning either device isn’t enough. You must use a heart rate monitor or a power meter properly to improve. Why not give either a try?
Co-founder at FLO Cycling. Jon manages the day to day operations and acts as the lead engineer for all FLO products.