Indoor Cycles
Introduction to Training with Power I’m Allen Lim, the Director of Education for the Saris Cycling Group. As part of my doctoral work at the University of Colorado at Boulder my peers and I at the Applied Exercise Science Laboratory conducted groundbreaking research investigating the role of power in optimizing cycling performance, using the Power Tap and other CycleOps products that are now available to the general public. Today, I’m actively involved in applying this research to help a broad range of individuals improve their health and performance through my work at Saris and at Thrive HFM ( www.thrivehfm.com) On this webpage I want to share with you some basic information to help you understand what it means to train with power, and how CycleOp products can help you to meet your personal fitness and/or competitive goals. Power & Power Measurement: Let’s start with defining power and talking about how it’s measured: Power Defined: •
Power is simply the amount of work or energy you expend in a given time frame and is measured as a watt.
•
Normally, work or energy is represented as a joule, while time is represented in seconds. So 1 watt is equal to 1 joule of energy per second while 100 watts is equal to 100 joules per second.
•
As a point of reference 1 horsepower is equal to 746 watts or 746 joules of energy per second. In contrast a professional cyclist like Floyd Landis can hold just over 400 watts for 30 minutes.
Measuring Power: •
On the bicycle, power can be measured as the amount of force or torque generated at the pedals or hub multiplied by the speed or angular velocity of the pedals or hub. So power output on a bicycle is simply a product of how hard you push on the pedals and how fast you are pedaling. To produce more power, you can either push harder or pedal faster.
•
The Power Tap works by measuring the amount of force at the rear hub using strain gauges embedded in the hub and by also measuring the speed of the hub.
•
On the bicycle, power is also a product of your speed and all of the forces that resist forward motion like aerodynamic resistance or wind, gravitational resistance or the grade of a given hill, rolling resistance or the quality and pressure in your tires, and the resistance in moving parts like your chain or bearings.
•
Practically speaking, the higher your power output the faster you go.
•
It’s important to note, however, that two individuals may produce very different power outputs to achieve the same speed because of differences in body and bicycle weight and in aerodynamics. For example, a heavier person will need more power or energy in a given time frame to go 15 mph up a hill compared to a lighter person. Likewise, riding in a more aerodynamic position like the drops will require less power at a given speed on a level road compared to riding in a poor aerodynamic position. Well talk about this more when we talk about how the Power Tap can be used as a virtual wind tunnel to estimate aerodynamic drag.
Power & Energy: •
Since power is really just a measure of energy over a given time frame, if you know your average power output and the duration of a given ride, you can calculate the amount of energy you use on that ride. The power tap does this continuously throughout a ride and represents that energy in Kilojoules or “Kj’s” where 1 Kjoule is equal to 1000 Joules.
•
There are a number of different ways to represent energy. A kilojoule is a mechanical representation of energy. In our everyday world, however, we typically represent energy, thermically, as the amount of heat released when burning a quantity of food. Thus, we normally think of energy in terms of the amount of food we can eat in kilocalories.
•
To get an idea of how many Kcals you burn for a given number of Kjoules of energy transferred to the bicycle, you need to know that 1 Kcal is equal to roughly 4 Kjoules (4.184). So if you do 1000 Kjoules on the bicycle, you’ve really transferred about 250 Kcals of energy to the rear hub. But that doesn’t mean that you’ve burned 250 Kcals worth of food. This is because while riding a bicycle, the average person is just under a quarter or 25% efficient. That means if you burn 1000 Kcals of food while riding a bicycle, only about 250 gets transferred to the hub to make the bicycle move. The rest just gets wasted as excess heat. So by a quirk of nature, 1000 Kjoules measured by the Power Tap is equal to just over 1000 Kcals burned by your body.
•
During a typical 5 hour stage in the Tour De France the average rider can do close to 4000 Kjoules of work and burn about 4000 Kcals worth of energy. In contrast, the Surgeon General currently recommends that the average American accumulate at least 1500 Kcals worth of exercise each week to maintain a healthy lifestyle. If you want to ride in the Tour, try and do 4000 Kjoules in 5 hours. If you want to stay healthy, just try and do 1500 Kjoules over the course of a week.
The Significance of Measuring Power and Energy: Stimulus vs. Response: •
A basic tenet in training is that there is a distinct relationship between an individual’s training load, or the training stimulus, and that person’s adaptive response or performance. First conceived by a German physiologist named Hans Selye, this “Stimulus-Response” relationship is generalized as an inverted U relationship, where too little and too much stimulus or training load results in sub-optimal performances. Simply put, if you don’t train, you won’t perform, but if you train too much you run the risk of breaking down and hurting your performance.
•
While the idea, that too little or too much stress can hurt performance, is well known, determining the optimal or perfect amount of training for a given individual is often the biggest single problem faced by athletes and coaches. One of the reasons this has been so difficult, is that until recently the tools and technology to easily measure the training stimulus has not existed in endurance sports like cycling, where variations in wind, terrain, and drafting, make speed and distance an inconsistent measure of the training load.
•
Because power output is an absolute and objective measure of the training stimulus or intensity, the advent of the Power Tap technology now makes it possible to accurately quantify an individual’s training load during training and competition.
•
In the same way that strength athletes can measure the actual mass that they lift in the gym, cyclists can now measure the actual power they produce when riding, rather than relying on responses that may or may not represent the actual load.
Power (Stimulus) vs. Heart Rate (Response): •
For over a century, power output was measured using expensive cycle ergometers. While this made cycling and measures of power one of the most commonly used models for studying exercise physiology, measures of power output, until recently, were the exclusive domain of the laboratory.
•
In the laboratory, there is a strong and linear relationship between power output and an individual’s heart rate response. That is, as power output increases in a controlled laboratory environment, heart rate also increases in a predictable fashion. Because of this strong relationship between power and heart rate in the laboratory, heart rate became a common way to measure exercise intensity outside of the laboratory in real world conditions. This assumed, however, that the relationship between heart rate and power output remained the same outside the laboratory.
•
Unfortunately, we now know that a number of factors can change the relationship between power output and heart rate outside of the laboratory. These factors include dehydration, heat stress, sudden increases and decreases in power output, fatigue, changes in a person’s fitness level, and the excitement of competition.
•
As a result, heart rate is not a good predictor of the training stimulus or power output in the field, especially in competitive events where power output can vary tremendously. This doesn’t mean that the heart rate response is un-important. It just means that the heart rate response should not be confused with the actual stimulus. Where power is the actual exercise stimulus, heart rate is one of many physiological responses.
•
In the past, when heart rate was used as the primary measure of the exercise stimulus, the basic training tenet of “StimulusResponse” was actually a “Response-Response” relationship. By monitoring both power and the resulting heart rate response, we can for the very first time, track the actual exercise stimulus as well as an important physiological response. This allows us to better track an athlete’s short and long term response to training. For example, in a single ride an increase in the heart rate response at a given output could be a sign of dehydration or fatigue, while a decrease in the heart rate response at a given power output over a year of training is a positive sign that one’s fitness has improved.
•
Not that power is the only measure and not that heart rate is a terrible measure, just that they represent two distinct things. The value of each is greatly enhanced by knowing one relative to the other. For example, on one day you might notice that your
heart rate is really high at 100 watts and that you feel terrible. A week later, you might find that your heart rate at 100 watts is significantly lower and that you feel better, indicating an improvement in your fitness.
Power Output Provides Objective Feedback: •
Ultimately, monitoring and evaluating power output during training and competition provides the most objective and immediate feedback about one’s performance. In the end, accurate and reliable feedback is a critical aspect of any training program whether you’re an Olympic athlete or just trying to lose a few pounds.
•
As an example, in the same way that thermal energy or heat can be measured with a thermometer, mechanical energy or power can be measured with a power meter. Using this analogy, if you wanted to bake a pie and you didn’t know the temperature, you might through trial and error eventually get a sense for how hot the oven needs to be to bake a perfect pie. If however, you had a simple tool like a thermometer to give you direct and immediate feedback, the learning curve for baking that pie would be greatly accelerated. In the same way, understanding your own response to training relative to an objective measure like power output takes the guesswork out of training because of direct, consistent, and immediate feedback.
Training with Power
Basic Principles Have Not Changed -- The Ability to Apply Them Has: •
The Power Tap does not change the basic nature of training, it simply allows you to quantify it and thus to actually implement training principles that until recently have largely remained theoretical constructs.
•
You still have to work hard if you want to improve. But for the first time, you can also work smarter by applying basic training principles that have been difficult to apply without power.
Specificity: •
A fundamental training principle is that training should be as specific to the demands of competition as possible. That is, your training should replicate either in parts or as a whole what happens in competition if you want to optimize your training for a given event.
•
Before the Power Tap technology, we could only describe the demands of an event in general terms using variables like the duration, terrain, features, and speed. Depending upon factors like the wind, weather, and tactics replicating things, especially if you didn’t have access to that course was extremely difficult.
•
Today, we can actually measure using the Power Tap, different aspects of a given race, such as the average power output, total energy required, and time spent in different intensity ranges. We can then use that information to develop better training strategies and to monitor whether our training is specific to our competitive goals.
•
In the same way that power helps athletes accomplish specific training goals that help them in competition, monitoring power output can help regular individuals accomplish specific health or fitness goals. For example, there are 3500 kcals in one pound of fat. If you want to lose weight, most doctors recommend that you not try to lose more than one pound per week. In order to do that, you would need decrease your food intake by 500 kcals each day or burn an extra 500 kcals through exercise each day. Because, dieting alone can lead to a decrease in muscle mass, and in turn slow your metabolism down and hurt your fitness, most doctors and physiologists recommend that you lose those extra calories through exercise. Using the Power Tap, you can create a very specific goal of riding at least 500 Kjoules each day. If you’re not in great shape and fairly small, it may take you two hours to do that 500 Kjoules. If you’re bigger and in better shape, it may only take you an hour. Regardless, you can match a specific training regime to the demands required for a specific goal.
Periodization: •
Another basic training principle is the idea of periodization of training that simply refers to the balance between hard days of training or overload and easy days of training or recovery.
•
Essentially, in order to adapt, the training stimulus needs to be greater than recently experienced – an idea referred to as overload. At the same time, any period of overload needs to be followed by a period of rest or recovery to allow the body to heal and grow stronger.
•
If done correctly, over time an individual’s training load looks very similar to a stock chart for a successful company. Despite periodic highs and lows, the general training load that person is able to handle continues to grow.
•
Before cyclist could accurately monitor training with power, creating proper periodization schedules was extremely difficult. Difficult, because, like an unstable economy, evaluating the value of currency or one’s training load was speculative at best.
Individuality: •
A training program that works well on one individual may not work as well on another. This idea is called individuality and reflects the unique genetic attributes of each individual.
•
Because every individual may respond differently to training, to reach a given fitness or performance goal, it is important to develop techniques and strategies for a given person to quickly and efficiently experiment with their own training rather than adopting strategies developed or tested in potentially dissimilar groups or individuals.
•
Since the Power Tap provides scientifically accurate that is specific to the individual user, with a Power Tap, you can figure out how a given training plan affects your performance rather than generalize from a program designed for a different person.
The Validity and Reliability of the Power Tap: External Dynamometer: •
Using a device called an external dynamometer that can generate and measure power, we were able to evaluate the accuracy of a number of randomly selected Power Taps. Against the external dynamometer and a scientific SRM we found that any given Power Tap is a consistent and valid measure of power output. Accordingly, no difference was found in the results of a single Power Tap when compared to the results of multiple Power Taps, demonstrating that the power measured in one Power Tap is the same as the power measured in another.
Improving Performance with a Power tap without Improving Fitness: Aerodynamics: •
Over a flat road on a windless day 90% of the resistance impeding forward motion on a bicycle is due to aerodynamic drag. As a result, a cyclist’s speed is largely a function of aerodynamic resistance and power output. Because, aerodynamic resistance also changes exponentially with speed, a small change in aerodynamic resistance created by a subtle change in body position or equipment can cause dramatic changes in power output at a given speed. For example, going from the hoods to the drops can save 30 to 50 watts at 25 mph, creating a time saving of 3 to 5 minutes in a 40 km time trial.
•
Because decreasing aerodynamic drag can dramatically improve performance, many professional cyclists pay large sums of money to optimize their body position and aerodynamics in a wind tunnel. Essentially, these athletes are attempting to decrease the power required for a given speed.
•
Using the Power Tap, the same improvements normally limited to a wind tunnel can be made by simply analyzing the relationship between power output and speed. For example, if a change in body position decreases the power required for a given speed than that body position is more aerodynamic. By experimenting with different body positions and measuring power, significant improvements can be made in aerodynamics and ultimately speed.
Pacing Strategy:
Tactics:
Power is simply the amount of work or energy you expend in a given time frame and is measured as a watt.
•
Normally, work or energy is represented as a joule, while time is represented in seconds. So 1 watt is equal to 1 joule of energy per second while 100 watts is equal to 100 joules per second.
•
As a point of reference 1 horsepower is equal to 746 watts or 746 joules of energy per second. In contrast a professional cyclist like Floyd Landis can hold just over 400 watts for 30 minutes.
Measuring Power: •
On the bicycle, power can be measured as the amount of force or torque generated at the pedals or hub multiplied by the speed or angular velocity of the pedals or hub. So power output on a bicycle is simply a product of how hard you push on the pedals and how fast you are pedaling. To produce more power, you can either push harder or pedal faster.
•
The Power Tap works by measuring the amount of force at the rear hub using strain gauges embedded in the hub and by also measuring the speed of the hub.
•
On the bicycle, power is also a product of your speed and all of the forces that resist forward motion like aerodynamic resistance or wind, gravitational resistance or the grade of a given hill, rolling resistance or the quality and pressure in your tires, and the resistance in moving parts like your chain or bearings.
•
Practically speaking, the higher your power output the faster you go.
•
It’s important to note, however, that two individuals may produce very different power outputs to achieve the same speed because of differences in body and bicycle weight and in aerodynamics. For example, a heavier person will need more power or energy in a given time frame to go 15 mph up a hill compared to a lighter person. Likewise, riding in a more aerodynamic position like the drops will require less power at a given speed on a level road compared to riding in a poor aerodynamic position. Well talk about this more when we talk about how the Power Tap can be used as a virtual wind tunnel to estimate aerodynamic drag.
Power & Energy: •
Since power is really just a measure of energy over a given time frame, if you know your average power output and the duration of a given ride, you can calculate the amount of energy you use on that ride. The power tap does this continuously throughout a ride and represents that energy in Kilojoules or “Kj’s” where 1 Kjoule is equal to 1000 Joules.
•
There are a number of different ways to represent energy. A kilojoule is a mechanical representation of energy. In our everyday world, however, we typically represent energy, thermically, as the amount of heat released when burning a quantity of food. Thus, we normally think of energy in terms of the amount of food we can eat in kilocalories.
•
To get an idea of how many Kcals you burn for a given number of Kjoules of energy transferred to the bicycle, you need to know that 1 Kcal is equal to roughly 4 Kjoules (4.184). So if you do 1000 Kjoules on the bicycle, you’ve really transferred about 250 Kcals of energy to the rear hub. But that doesn’t mean that you’ve burned 250 Kcals worth of food. This is because while riding a bicycle, the average person is just under a quarter or 25% efficient. That means if you burn 1000 Kcals of food while riding a bicycle, only about 250 gets transferred to the hub to make the bicycle move. The rest just gets wasted as excess heat. So by a quirk of nature, 1000 Kjoules measured by the Power Tap is equal to just over 1000 Kcals burned by your body.
•
During a typical 5 hour stage in the Tour De France the average rider can do close to 4000 Kjoules of work and burn about 4000 Kcals worth of energy. In contrast, the Surgeon General currently recommends that the average American accumulate at least 1500 Kcals worth of exercise each week to maintain a healthy lifestyle. If you want to ride in the Tour, try and do 4000 Kjoules in 5 hours. If you want to stay healthy, just try and do 1500 Kjoules over the course of a week.
The Significance of Measuring Power and Energy: Stimulus vs. Response: •
A basic tenet in training is that there is a distinct relationship between an individual’s training load, or the training stimulus, and that person’s adaptive response or performance. First conceived by a German physiologist named Hans Selye, this “Stimulus-Response” relationship is generalized as an inverted U relationship, where too little and too much stimulus or training load results in sub-optimal performances. Simply put, if you don’t train, you won’t perform, but if you train too much you run the risk of breaking down and hurting your performance.
•
While the idea, that too little or too much stress can hurt performance, is well known, determining the optimal or perfect amount of training for a given individual is often the biggest single problem faced by athletes and coaches. One of the reasons this has been so difficult, is that until recently the tools and technology to easily measure the training stimulus has not existed in endurance sports like cycling, where variations in wind, terrain, and drafting, make speed and distance an inconsistent measure of the training load.
•
Because power output is an absolute and objective measure of the training stimulus or intensity, the advent of the Power Tap technology now makes it possible to accurately quantify an individual’s training load during training and competition.
•
In the same way that strength athletes can measure the actual mass that they lift in the gym, cyclists can now measure the actual power they produce when riding, rather than relying on responses that may or may not represent the actual load.
Power (Stimulus) vs. Heart Rate (Response): •
For over a century, power output was measured using expensive cycle ergometers. While this made cycling and measures of power one of the most commonly used models for studying exercise physiology, measures of power output, until recently, were the exclusive domain of the laboratory.
•
In the laboratory, there is a strong and linear relationship between power output and an individual’s heart rate response. That is, as power output increases in a controlled laboratory environment, heart rate also increases in a predictable fashion. Because of this strong relationship between power and heart rate in the laboratory, heart rate became a common way to measure exercise intensity outside of the laboratory in real world conditions. This assumed, however, that the relationship between heart rate and power output remained the same outside the laboratory.
•
Unfortunately, we now know that a number of factors can change the relationship between power output and heart rate outside of the laboratory. These factors include dehydration, heat stress, sudden increases and decreases in power output, fatigue, changes in a person’s fitness level, and the excitement of competition.
•
As a result, heart rate is not a good predictor of the training stimulus or power output in the field, especially in competitive events where power output can vary tremendously. This doesn’t mean that the heart rate response is un-important. It just means that the heart rate response should not be confused with the actual stimulus. Where power is the actual exercise stimulus, heart rate is one of many physiological responses.
•
In the past, when heart rate was used as the primary measure of the exercise stimulus, the basic training tenet of “StimulusResponse” was actually a “Response-Response” relationship. By monitoring both power and the resulting heart rate response, we can for the very first time, track the actual exercise stimulus as well as an important physiological response. This allows us to better track an athlete’s short and long term response to training. For example, in a single ride an increase in the heart rate response at a given output could be a sign of dehydration or fatigue, while a decrease in the heart rate response at a given power output over a year of training is a positive sign that one’s fitness has improved.
•
Not that power is the only measure and not that heart rate is a terrible measure, just that they represent two distinct things. The value of each is greatly enhanced by knowing one relative to the other. For example, on one day you might notice that your
heart rate is really high at 100 watts and that you feel terrible. A week later, you might find that your heart rate at 100 watts is significantly lower and that you feel better, indicating an improvement in your fitness.
Power Output Provides Objective Feedback: •
Ultimately, monitoring and evaluating power output during training and competition provides the most objective and immediate feedback about one’s performance. In the end, accurate and reliable feedback is a critical aspect of any training program whether you’re an Olympic athlete or just trying to lose a few pounds.
•
As an example, in the same way that thermal energy or heat can be measured with a thermometer, mechanical energy or power can be measured with a power meter. Using this analogy, if you wanted to bake a pie and you didn’t know the temperature, you might through trial and error eventually get a sense for how hot the oven needs to be to bake a perfect pie. If however, you had a simple tool like a thermometer to give you direct and immediate feedback, the learning curve for baking that pie would be greatly accelerated. In the same way, understanding your own response to training relative to an objective measure like power output takes the guesswork out of training because of direct, consistent, and immediate feedback.
Training with Power
Basic Principles Have Not Changed -- The Ability to Apply Them Has: •
The Power Tap does not change the basic nature of training, it simply allows you to quantify it and thus to actually implement training principles that until recently have largely remained theoretical constructs.
•
You still have to work hard if you want to improve. But for the first time, you can also work smarter by applying basic training principles that have been difficult to apply without power.
Specificity: •
A fundamental training principle is that training should be as specific to the demands of competition as possible. That is, your training should replicate either in parts or as a whole what happens in competition if you want to optimize your training for a given event.
•
Before the Power Tap technology, we could only describe the demands of an event in general terms using variables like the duration, terrain, features, and speed. Depending upon factors like the wind, weather, and tactics replicating things, especially if you didn’t have access to that course was extremely difficult.
•
Today, we can actually measure using the Power Tap, different aspects of a given race, such as the average power output, total energy required, and time spent in different intensity ranges. We can then use that information to develop better training strategies and to monitor whether our training is specific to our competitive goals.
•
In the same way that power helps athletes accomplish specific training goals that help them in competition, monitoring power output can help regular individuals accomplish specific health or fitness goals. For example, there are 3500 kcals in one pound of fat. If you want to lose weight, most doctors recommend that you not try to lose more than one pound per week. In order to do that, you would need decrease your food intake by 500 kcals each day or burn an extra 500 kcals through exercise each day. Because, dieting alone can lead to a decrease in muscle mass, and in turn slow your metabolism down and hurt your fitness, most doctors and physiologists recommend that you lose those extra calories through exercise. Using the Power Tap, you can create a very specific goal of riding at least 500 Kjoules each day. If you’re not in great shape and fairly small, it may take you two hours to do that 500 Kjoules. If you’re bigger and in better shape, it may only take you an hour. Regardless, you can match a specific training regime to the demands required for a specific goal.
Periodization: •
Another basic training principle is the idea of periodization of training that simply refers to the balance between hard days of training or overload and easy days of training or recovery.
•
Essentially, in order to adapt, the training stimulus needs to be greater than recently experienced – an idea referred to as overload. At the same time, any period of overload needs to be followed by a period of rest or recovery to allow the body to heal and grow stronger.
•
If done correctly, over time an individual’s training load looks very similar to a stock chart for a successful company. Despite periodic highs and lows, the general training load that person is able to handle continues to grow.
•
Before cyclist could accurately monitor training with power, creating proper periodization schedules was extremely difficult. Difficult, because, like an unstable economy, evaluating the value of currency or one’s training load was speculative at best.
Individuality: •
A training program that works well on one individual may not work as well on another. This idea is called individuality and reflects the unique genetic attributes of each individual.
•
Because every individual may respond differently to training, to reach a given fitness or performance goal, it is important to develop techniques and strategies for a given person to quickly and efficiently experiment with their own training rather than adopting strategies developed or tested in potentially dissimilar groups or individuals.
•
Since the Power Tap provides scientifically accurate that is specific to the individual user, with a Power Tap, you can figure out how a given training plan affects your performance rather than generalize from a program designed for a different person.
The Validity and Reliability of the Power Tap: External Dynamometer: •
Using a device called an external dynamometer that can generate and measure power, we were able to evaluate the accuracy of a number of randomly selected Power Taps. Against the external dynamometer and a scientific SRM we found that any given Power Tap is a consistent and valid measure of power output. Accordingly, no difference was found in the results of a single Power Tap when compared to the results of multiple Power Taps, demonstrating that the power measured in one Power Tap is the same as the power measured in another.
Improving Performance with a Power tap without Improving Fitness: Aerodynamics: •
Over a flat road on a windless day 90% of the resistance impeding forward motion on a bicycle is due to aerodynamic drag. As a result, a cyclist’s speed is largely a function of aerodynamic resistance and power output. Because, aerodynamic resistance also changes exponentially with speed, a small change in aerodynamic resistance created by a subtle change in body position or equipment can cause dramatic changes in power output at a given speed. For example, going from the hoods to the drops can save 30 to 50 watts at 25 mph, creating a time saving of 3 to 5 minutes in a 40 km time trial.
•
Because decreasing aerodynamic drag can dramatically improve performance, many professional cyclists pay large sums of money to optimize their body position and aerodynamics in a wind tunnel. Essentially, these athletes are attempting to decrease the power required for a given speed.
•
Using the Power Tap, the same improvements normally limited to a wind tunnel can be made by simply analyzing the relationship between power output and speed. For example, if a change in body position decreases the power required for a given speed than that body position is more aerodynamic. By experimenting with different body positions and measuring power, significant improvements can be made in aerodynamics and ultimately speed.
Pacing Strategy:
Tactics:
