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Training with Power:
Frequently Asked Questions 

By Hunter Allen

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Les Woodland's book Cycling's 50 Craziest Stories is available as an audiobook here. For the print and Kindle eBook versions, just click on the Amazon link on the right.

Hunter Allen writes:

What is Power?
Power is a direct measure of the rate of work produced by a cyclist; that is, how hard a cyclist is pushing on the pedals multiplied by how fast they are pedaling.  Power is measured by use of a power meter such as SRM, Quarq and PowerTap.  Imagine a cyclist as the engine for a bike and the power meter tells you how much horsepower you are  creating in the form of watts much like a car engine is measured as horsepower. 1 Horsepower= 746 watts.

What is a Watt?
A Watt is a unit often used to describe the instantaneous power a household appliance uses any one moment. A watt is also a unit of measurement of the work that can be done by a cyclist. Watts can also be referred to as “power”, which is work divided by time

What does it mean to train with Power?
When power data is analyzed in a training software program such as TrainingPeaks, coaches and riders can begin to determine Functional Threshold Power (FTP), Power levels and determine strengths and weakness of an athlete. Incorporating power into a training program provides a coach or cyclist the exact data to develop individualized training programs, develop specific workouts based on wattage and make decisions on when to stop an interval, when to take a rest day or when to tackle greater challenges- all guided by the power data.

How is training with power different than training with Heart Rate? 
Heart Rate measures the body’s response during a workout while Power measures the training dose that created the response.  Heart Rate measurement only tells us how fast our heart is beating, but doesn’t tell us how much work (power) we are creating. A cyclist could be on the start line of a race and just the anticipation of the race might cause a heart rate response of 160 beats per minute, but no actual work is being done.  Training with power allows the cyclist to quantify the actual workload(dose) and then learn if that workload creates the desired response (in this case: Improvement) (Essentially, the watts a rider produces is the work that drives a bicycle forward and the heart rate is the body’s response to that work.. 

What is TSS? 
Training Stress Score (TSS) is a way of expressing the workload from a training session. It is the product of the workout’s intensity and duration. As either of these increases, TSS also increases. A 100% ‘best’ effort for one-hour equals 100 TSS points, no matter who you are and this allows us to compare different workouts between each other knowing a relative measurement.

What is Normalized Power?
Normalized power combines two factors:

• Physiological responses to rapid changes in intensity follow a time course that is predictable
• Many physiological responses (e.g. lactate production, glycogen utilization, etc.) are not linear when related to exercise intensity. 

For example, a ride that has massive accelerations and then lulls (perhaps a criterium) will be more demanding on an athlete’s energy systems than a ride that is much more steady – even though they may average out to being the same wattage in the end. Normalized Power is basically an estimate of the power that you could have maintained for the same physiological “cost” if your power output had been constant.   

What is Functional Threshold Power?
The average power for a full 60-minute effort is known as Functional Threshold Power (FTP). This is the starting point that all workouts are compared to in order to calculate the intensity (IF-Intensity Factor) of the ride. A rider in the breakaway will have a higher IF than a rider relaxing in the field.  IF will equal 1.0 when a rider is riding at their FTP and similarly a rider riding at an IF of .87, means they are riding at roughly 87% of their FTP.

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