Question: Should I train and race with a heart rate monitor or a power meter? What are the pros and cons?

For mountain bike training, I recommend using a power meter, perceived exertion and a heart rate monitor. The more data you have, the more tools you have at your disposal to measure performance and improve your training. 

The Bottom Line
Use a power meter extensively in training to best mimic racing demands, track measured changes in fitness, nail training objectives, and effectively calibrate perceived exertion with reality.  Changes in power output give you a direct, objective measure of the effectiveness of your training plan.  Heart rate will let you know you are alive.

Direct vs. Indirect
Power (Watts) is a direct measure of exercise intensity, whereas heart rate is an indirect measure of exercise intensity. Heart rate is a response to exercise and other factors (heat, humidity, altitude, diet, caffeine, stimulation, motivation, fatigue, time of day/night).

Crystal Clear vs. Crystal Ball?
Performance is accurately measured with power. Power data is crystal clear. You either produced the watts or you did not. Heart rate data requires guess work to interpret the result due to the many variables included. A crystal ball may be helpful in order to draw real conclusions from heart rate data.

Immediate vs. Time Lagged
Power has an immediate reaction to changes in exercise intensity. Heart rate has a time lag of about 30 seconds in its response to changes in exercise intensity. This makes heart rate a useless pacing tool for efforts of less than 30 seconds and for the first 30 seconds of any longer interval. Heart rate encourages athletes to over-pace at the start of an interval in order to quickly get their heart rate into the target zone. When training with power you can immediately peg the exact goal exercise intensity and train with accuracy.

Here’s an example:  The goal in the following workout was to maintain a steady power of 265 Watts.  The rider also wore a heart rate strap, so we have both sets of data.

Not only does heart rate lag effort by 30 seconds, it can also creep upward over time.  Imagine if this rider didn’t have the benefit of the power readings, and instead attempted to drive HR up to 165bpm in the first few minutes.  The result would likely have been an interval ending meltdown about 18 minutes in, and at the very least a drastic reduction in power in the 2^nd half of the interval.

Software
There are several software applications available to crunch your power data. They will analyze, interpret and summarize. You can look at how fast and hard you are pedaling with Quadrant Analysis (QA) to see if you are mimicking the demands of racing in your training. You can get a measure of the intensity of a ride (IF), the variability of a ride (VI) and the training stress (TSS) of a ride.

Performance Manager Chart (PMC)
PMC is a valuable tool for mountain bikers. It uses ride TSS scores, averaging them over days and months. Analyzing a single ride is like looking at a single tree in a forest. You get a nice picture of that tree but don’t know where it sits in the forest. The beauty of the PMC is that it tallies up TSS over time to give a bird’s eye view of the forest – or your entire season (or even cycling career). The PMC can be used retroactively to look at scores during times you had personal best performances and during times you thought you should have but didn’t. It can be used for forward planning to target a specific set of scores known to put you in peak form and to time that peak form to land smack bang on race day. The PMC takes much of the guess work out of training, tapering and peaking.

Racing
Whether or not to race with a power meter depends on the priority of your race. In low priority training races, go for the power meter.  Race data often uncovers one’s strengths and weaknesses, and can also turn up some surprising finds with regards to race demands.  Race files are a powerful piece of the training puzzle.

As an example, using Quadrant Analysis (a feature of WKO+ 3.0) with power meter data from single speed mountain bike races shows a particularly high concentration of power in the VO2max range with cadences below 60. This means pedal forces are much higher on average than when riding with gears.  This has led to some novel training methods for single speeders.

Goal events are different.  By the time you have reached a fitness peak, all those hours of training with a power meter have worked to “calibrate” your perceived exertion (PE).  PE is your best option for pacing goal events. You’ll know what you can do and for how long, and with enough experience, PE alone will guide you to your best results.

Potential drawbacks to mountain bike racing with a power meter
Power meter and heart rate monitors are not 100% reliable. How will you pace the event if your gadget malfunctions?

Power meters are heavier than race-weight wheels or cranks.

The highly variable nature of power production in mountain bike races makes it quite difficult to turn the real time power data into actionable information.  Short accelerations and race starts are deep into anaerobic power levels, even for longer endurance events.  It is tough to make sense of the numbers without software.

Mountain bike race starts are mayhem. The place for your eyeballs during a race start is on the trail, your surroundings and fellow racers and not on a little monitor screen.

Power meters can even make you slower in a peak race!
More importantly, pacing with a power meter may actually hold you back from a breakthrough performance! On a top priority race day your body should be in peak condition; trained, tapered, fueled, hydrated and ready to go. You should be poised to set records by producing more power and going faster than ever before. Pacing yourself using power numbers established in training may act as a governor on your peak day and could hold you back from a potential record performance.

Post Race Analysis
There is often quite a difference between what you think you did in a race (or, what you tell your coach you did) and what you actually did. Power data tells all! You can learn how to pace races more accurately and how to repeat outstanding performances from the data. Race data is useful in learning how much power you needed to win a certain race and in what pattern that power was created. This type of information is valuable in order to design better training plans and improve future performances.

Without a doubt, train with a power meter.  Also, race your lower priority events with the power meter to help objectively assess your strengths and weaknesses, helping you dial in your training for the goal event(s).  For peak priority races use your lightweight race equipment and rely on a well calibrated sense of PE to reach new performance heights.

Lynda Wallenfels is a USA Cycling Cat 1 certified cycling coach and pro mountain bike racer. She is owner of LWCoaching.com. She always trains and often races with a power meter.

If you are using the Garmin Edge 705 with a power meter things just got a bit easier to track.  Ever since I began using the 705/PT combo, I’ve still used the PT CPU for rides where I really wanted to know the workouts details.  WKO has until now not handled stops in the ride correctly.

Build 106 of WKO+ is a big step in the right direction.  This latest version was released a couple of days ago.  If you set the 705 to auto-pause, WKO+ will now interpret those pauses exactly as it does for the PT CPU.  Finally, we get our cake and get to eat it as well.

Get the latest build here:

http://home.trainingpeaks.com/wko-desktop-software/download.aspx

By overwhelming demand from wattage users, they have also started publishing release notes.  Prior to this the only way to see the release notes was to install the program.  Do you really want to install every release to make sure you’ve got what you need?  They support something like 68 devices so most of the updates are related to device compatibility anyway.

Check the release notes here to determine if you need the latest:

http://support.trainingpeaks.com/trainingpeaks-wko/release-notes-for-wko.aspx

Last October Saris began taking orders for a hub update device for their 2.4 wireless power meters.  Typically the firmware in the electronic power measuring hubs never needs updates, so this is a special gizmo.  The update?  The hub transmissions are changed to include both the private Saris network and the ANT+ Sport network.

For many PT wireless users this falls in the “so what” category.  It doesn’t make the hub work any better with the existing PT CPU.  What it will do, however, is enable 3rd party ANT+ Sport devices to receive PT transmissions in a recognizable format.  The Garmin 705 is one such device, and others could possibly include the wireless SRM receiver,  iBike/iAero, and the forthcoming unit from Quark.

Combining the power data of the PT with other devices has several potential benefits.  The iAero/PT combo has great potential for roadies in optimizing bike position through reduced air drag.  The Quark is supposed to be linux based and open source, allowing customized algorithms & displays for the extreme geek.  The 705 is a GPS mapping unit as well as hosting all the training utility of the 305 Edge units – for off-road GPS users, the combination with power is sexy indeed!

Finally the updater began shipping in Dec.  The actual update is as easy as changing the batteries.

Remove the disc and black battery cover.  Remove the battery pack.  Insert the updater into battery pack connector.

Flip the little switch and red/green LEDs begin alternating inside the unit.

When it’s done the light turns green steady.

Turn it off.  Remove it, replace the battery pack (great time to replace batteries too), put the new cover on that came with the updater, reinstall the disc and that’s about it.

First time on the bike you may need to relearn the hub.

Now for the gotchas.  Of course there are a few.

I’m using the Garmin 705.  It turns out they decided to filter the raw data stream, likely due to the PT’s aliasing.  The PT calculates power data points at fixed time intervals which basically means that depending on what cadence you ride at, the point to point value fluctuations can be quite large.  Filtering the data stream makes sense for noisy GPS signal perhaps, but filtering the PTs data stream generates bogus data for bursty efforts.  I’ve been in contact with Garmin, they have removed the filter in a beta version that I’ve been testing and so far so good.  I can’t say when it will become publicly available, but it should be very soon.

Zeroing the torque is now a different process.  It is done at the hub and not the CPU, and must be done while the wheel is not moving.  At first glance this doesn’t make a lot of sense as the auto-zero function used to work at zero cadence, but now will need zero speed – and at zero speed how can zero torque be known by the hub?  It can’t.  Ever trackstand at a light, or rest your foot on the pedal?  Time will tell how well this works in practice.

Garmin 705 .tcx file format is a floating target.  Software such as Topofusion and WKO+ that rely on consistent file formats to produce meaningful data interpretations are having a tough time keeping pace.  Your favorite program may or may not work well with the Garmin if you choose to use it.

Whew, what a spew.  So there’s the scoop.  Power up and power on in ‘09.

I’ve been rolling my mtb disc 2.4 wireless PowerTap hub in circles since April with the factory installed batteries. About 15 hours of riding ago the battery low icon started to flash. Tomorrow I have a ride planned I really want to have power data for and would be bummed if it pooped out mid workout.

Changing the hub batteries requires first removing the disc.

Then unscrewing the battery cover with the cute tool provided with the PT.

Here is what it looks like inside.

There is a little battery pack that pops out.

The batteries took a bit of wiggling to get out but the new ones slid right in.

Then reverse all motions. The process was painless except for getting the plastic battery cover back on. It screws down on metal threads and was tough to get aligned and screwed down without crossing threads. That took a few extra minutes of wiggling too.

Once back together the system was ready to roll. No further finagling required. I should be good to go for another 400 hours of PowerTap love. Tomorrow is only scheduled for 90 mins…