Rubber Side Down | Power: The Best Kind of Data

Last week in our Rubber Side Down column, my comrade Brett wrote about the merits of using a heart rate monitor (read the article here: Heart Rate). For those new to cycling or triathlon, determining your heart-rate specific training zones and doing workouts according to these zones is the easiest and most practical way of becoming more scientific about training. While heart rate does provide valuable data, it does have its drawbacks when used by itself. One of the biggest drawbacks of training solely with heart rate is a phenomenon known as cardiac drift.

In laymen’s terms, cardiac drift is simply an experience where as your workout gets longer (over 2 hours), your heart rate steadily gets higher as your pace stays the same. This can be due to a number of factors; dehydration, fatigue, heat, etc. Heart rate also lags as efforts change: most commonly there is 15 to 30 seconds of lag with an additional 2 to 3 min stabilization period. With all of these potential drawbacks of using strictly heart rate, someone looking for a more scientific and stable data point should look at purchasing a power meter to use in conjunction with heart rate.

A power meter measures a rider’s output in watts, or cadence multiplied by torque. What makes power so useful is that it is not affected by biological factors. Assuming your meter is calibrated correctly, watts are always watts whether you’re fatigued or fresh, sleep deprived or well rested, etc. Using these two systems together though, will allow you to better see when you need rest, when you should train hard, all while tracking the progress of your fitness.

Just like with a heart rate monitor, there is an easy (but more accurate) way of determining one’s training zones via a power meter, and you don’t need a master’s degree in calculus to do it; but before we get into that, you’ll need to first select a power meter.

Step 1: Find the Right Power Meter For You

Picking a meter can be the hardest part of one’s power meter experience; with so many options, what does one choose? Below you will find how to get the best bang for your power-purchase buck:

  • Crank Based Systems

comp2Pros: lightweight, ability to use different wheelsets

Crank based systems such as Rotor’s 3D+ Power offer the best in the business as far as weight and accuracy are concerned. Those seeking a crank-based system on a budget may want to check out Sram’s Quarq S975 as it has all the benefits of a crank based system (minus a few features) at a lower price point. The big benefit of crank based systems are that you can run any wheelset you want or switch to a race wheelset without it having any effect on your power meter.

  • Hub Based Systems:

powertapPros: Low price, ability to swap between bikes

Hub based power meters, such as Powertap’s G3 Alloy Wheelset, are the most economical way to get into training and racing with a power meter. Wheels are much easier to swap between bikes than cranks, so for triathletes training on time trial and road bikes, this may be the best option. Just keep in mind that if you have a different wheelset that you want to run on race day, you won’t have a power meter to use unless the wheelset has a rear hub with the power meter built in. This means that if you want two different wheelsets and what a hub based power meter, you’ll need to essentially buy two power meters.

  • Pedal Based Systems:

pedalsPedal based power meters such as the Garmin Vector are the newest on the block. Even though the prices are comparable to crank based power meters, they have some added benefits. The Garmin pedals measure power output from each leg and that data can be crucial for both training and racing. Another benefit is the ease of being able to switch the pedals from one bike to another. For those of us who use one bike for training and another for racing, using a Garmin Vector eliminates any changes in important characteristics in how your bikes are set up. Unfortunately there isn’t a Speedplay version of these pedals available. So if you are dead set on Speedplay pedals, then you’ll need to choose one of the other two options for measuring power.

  • Computers:

comp1Almost all power meters are ant+ compatible, so good news for you if you went out and bought a Garmin Forerunner 910XT or a Garmin Edge 510 Performance Bundle after reading last week’s article on heart rate, because these two devices will easily sync to an ant+ capable power meter.

Step 2: Determine Functional Threshold Power (FTP)

dudeWhile “functional threshold power” may seem intimidating or complicated it’s simply defined as the power than one can hold for an hour-long maximal effort; and determining it is very simple. In their book “Training and Racing with a Power Meter,” Hunter Allen and Andrew Coggan, PhD, lay out a simple test:

  1. 20 minutes easy warm up
  2. 3 x 1-minute wind ups with a minute rest between (100ish RPM pedal cadence)
  3. 5 minutes easy
  4. 5 minutes all out (hard at first, but not so hard that you can’t complete the effort)
  5. 10 minutes easy
  6. 20-minute time trial effort (like the previous 5-minute effort, hard but steady)
  7. 10 to 15 minute cool down

Some of you may be asking “why on earth would I want to endure the pain of 20 minutes all out, when all I get is this thing called FTP”? Well there is a method behind the madness: FTP is used to determine specific training zones, much like the heart rate formula, but a bit more detailed.

Step 3: Determine Training Zones

Setting personal training zones are the key to developing your weekly training schedule, and to increasing fitness. A coach can help you to dial in zones that are best for you, but here are some general guidelines:

  • Zone 1 Active Recovery = < 55% of FTP (Active Muscle Recovery)
  • Zone 2 Endurance = 56-75% of FTP (Fat Burning/Aerobic Conditioning/LSD Training)
  • Zone 3 Tempo = 76-90% of FTP (Fartlek Workout)
  • Zone 4 Lactate Threshold = 91-105% of FTP (Time Trial Efforts 10-30 min)
  • Zone 5 VO2 Max = 106-120% of FTP (Increase VO2 Max 3-8 minutes)
  • Zone 6 Anaerobic Capacity = 121-150% of FTP (30s to 3 min efforts)
  • Zone 7 Neuromuscular Power = maximum effort

Implementing all of these zones into a weekly training schedule will allow you to get the most out of your power meter and become a better all-around rider, especially when used in conjunction with the tips from our article on Heart Rate. Using both methods of bio-feedback allows the rider to get the most data, and as everyone knows; more is better!

While training with a power meter may seem complicated, simply following the above-mentioned steps will get rid of the complications and help you to reach fitness levels that you never thought possible.