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Training with a
Powertap Hub

What is a Powertap?
A Powertap hub replaces the rear hub on your road bike. Inside the hub, there's a strain gauge that measures how much torque you're putting into the spokes. A magnet determines wheel RPM (just like a standard bicycle speedometer). From torque and RPM, the computer calculates how many watts of power you're delivering.

The unit comes with a heart rate monitor. Knowing both heart rate and power output lets you train more efficiently and monitor your progress with real numbers.

There's also an attachment for your crank that measures your pedaling cadence. This lets you find the gearing and the pedaling speed that gives you the best sustained power output.

You may also learn how seat position and handlebar position affect your ability to deliver power to the pedals. For example, even without considering wind resistance (testing on a trainer inside), I can deliver 10 to 20 watts more average power at the same heart rate and exertion level if I'm down in the drops of the road bike, rather than on the hoods.

The display unit is like an oversized bicycle computer. You can set up the display to meet the needs of your current workout or test.

After the workout, you can download the data to your computer for analysis.

A Powertap is expensive. The best strategy is to find a roadie who has one, and who will let you test yourself on his/your trainer. Once you've established your heart rate training zones with a baseline GXT and Power Profile, you create your workout plan. Then you go back to re-test yourself once a month as you prepare for the racing season.

Fitness Testing
Graded Exercise Test

The Graded Exercise Test (GXT) measures cardiovascular fitness. It shows your body's response to increasing workload. It can also identify lactate threshold wattage and heart rate. Each minute, you push 20 more watts, while recording heart rate, perceived exertion level, and ventilation comfort.

At right is the raw data as recorded during a GXT session. Below is the plotted data.

The GXT can be used monthly to show improving cardiovascular fitness, higher lactate threshold, and higher steady-state power output.

GXT Data Sheet
GXT Graph Sheet

A plot of heart rate versus power shows the cardiovascular response to increasing workload. The lactate threshold heart rate is about 10-15% below the point where breathing becomes labored (perceived exertion about 7/10). Heart rate training zones (and wattage training zones) can be calculated for recovery, endurance, lactate threshold, and anaerobic power. The GXT can follow both cardiovascular fitness and power delivery. This graph shows a hypothetical second test one month later. The line has shifted down and to the right. Each power step is achieved at a lower heart rate. Lactate threshold is reached at a higher wattage, meaning you can ride faster in a long race. The peak power achieved has also increased. This shows improved fitness.
Power Profile

Power Profile testing shows what you're capable of. If you're always bailing off your bike on those very short but very steep climbs, you need to improve your 12-second (0.2) power. For a rolling course like Five Mile Pass, you're looking for improvement in your 1-minute power. For ride that's mostly flat (for example, the ULCER) you look for improvement in the 12- and 30-minute power.

In addition to monitoring improvement, the Power Profile lets you match power output to the course, so you don't "blow up." From the graph at right, you could predict that for a 3-minute hillclimb, the rider could maintain about 350 watts average power.

Power Profile Data Sheet
Power Profile Graph Sheet

Time Trials

You can run a time trial based on either a fixed distance (for example 3 miles), or a set time (example 20 minutes). The test should be done while rested (during a recovery week), under similar conditions -- same course, same time of day, same wind and temperature conditions, etc. You're looking for higher average speed and higher average power.

Time Trial Data Sheet

Training with the Powertap
Every rider is different. The key to improving is to match your workouts to your own recovery ability, anaerobic strength, and aerobic fitness. It's not a simple thing to do that. A heart rate monitor is the most important addition to your standard bicycle speedometer. The Powertap adds another layer of science to your workout plan.
If you're rich enough and motivated enough to buy a Powertap, you can use it to improve the efficiency of your workouts. For example, if you're trying to increase your power at Lactate Threshold (which is your primary goal for cross-country racing), the computer lets you stay in the power zone and heart rate zone that will give you the biggest bump.
If your goal is power improvement, you can fine-tune the wattage to get the maximum growth stimulus to your muscles while minimizing muscle damage. Hit the muscles, but minimize the amount of time you'll need for recovery before the next workout.
And what about the day when your heart rate is way up there, and you feel you're working really hard, yet the hub shows pathetic power delivery compared to previous training sessions? Well, it's telling you to abort the training session, because your recovery isn't complete from the last one. There's nothing to gain from continuing.
To use a Powertap to match interval training to your current fitness level, go to the Anaerobic Interval Training page.
Race Training Specific Guidelines Intervals Resistance Trainers Upper Body Lower Body