power meters

How Accurate is the Calorie count on your Garmin?

To be frank, your Garmin is lying to you about the calories you have burned.  If you have a power meter, than it is still going to be much better than just about every calorie counting machine you’ll find in a gym, but gym machines aren’t really the topic here.  Let’s take a quick look at how Garmin computers and the Strava app do at calculating your total calories burned. Power meter such as an SRM can calculate your total work done during your ride, essentially power X time= total work.     Basically, if you ride at 150 watts for an hour, you do the same amount of work as if you ride at 300 watts for half an hour.   Your Garmin or other training device will display this as Kilojoules, or KJ.  KJ and Calories are both units of energy, and one can be converted to the other.  Many people will simply take the number of KJ and say that is the number of calories burned.    While that the total number of KJ is close to the number of calories burned,  KJ and Calories are not the same thing.

For starters the KJ measured by the powermeter are  a measurement of the mechanical work that was put into the bicycle.   Your body is really only about 21% efficient at creating mechanical work from the food energy.   So in reality, you need to multiply the total KJ of work by 4.8.    So if you did 1000 KJ worth of mechanical work, it actually took 4800 KJ in food energy to do that work.   Next you have to convert from KJ to Calories.  This is sort of like converting feet to meters.   One Calorie is equal to 4.184 KJ, so  you need to divide 4800 KJ by 4.184, and you get 1147 Calories.

If you simply looked at your Garmin, and assumed that KJ = Calories, you would have underestimated by 147 calories, or nearly 15 %( In reality is probably somewhere between 13 and 15%).    I can understand how early powermeter users simply looked at total KJ, and used it as a proxy for calories.   They probably considered it close enough.    But considering the fact that a modern bike computer is capable of doing  some fairly complex calculations in real time,  it seems silly  to work with this assumption.   Unfortunately, it appears that is exactly what Garmin is doing.    For  more explanation on  mechanical energy, food energy, and garmin’s KJ to Calories gooof, see this excellent blog  post by Jose  Areta.

Now on to my little experiment( N=1):

I started off a ride with a Garmin 500  synced to my SRM,  a Garmin 800 that was not synced to any  other training devices, and the Strava app on my IPhone.    The ride was from my house to the top of Mt Soledad, a local 700 foot climb.  I kept it at endurance pace for the most of the ride, and tempo pace up the climb.

The Garmin 500 really should be giving the most accurate calorie count, as it was the only device that could accurately measure KJ.  Unfortunately, Garmin makes the mistake of simply converting the KJ into Calories.   It seems absurd that they would make  that mistake, when all it would take to make a  more accurate calorie count would be to multiply KJ by 1.15 to get a much more accurate calorie count.

Total  Calories burned according to the Garmin 500 synced to the powermeter: 1075 Calories

More accurate calorie count (1075 KJ X1.15):  1236 Calories

Error:  Underestimate by ~15%


Next, was the Garmin 800 that wasn’t synced to anything else.   I’m not exactly sure what Garmin uses to estimate calories, but it must be some function of speed and elevation.     Unfortunately the Garmin doesn’t  “know” if I have a headwind or tailwind, if I’m drafting or riding solo, if I’m in the drops or sitting upright.     My expectations for an accurate calorie count were quite low.

Total calories burned according to Garmin with no  power : 1906

Error: overestimate by 54%


Whoa!  If you were using this to get an idea on how much you should eat to be Calorie neutral, you could be in big trouble!   Even if you were trying to have a 500 calorie deficit each day, you would be sorely disappointed.   Imagine meticulously measuring your food and calculating your energy expenditure, only to find out that  rather than having a 500 Calorie deficit each day, you actual had a surplus.      Do you think it will be any better if you measure heart rate?  Not According to Jose.  This is  a situation where bad data is worse than no data.    I have zero confidence in the calorie count of a Garmin without a power meter.   Zero.

What about the Strava app?    I suspect that Strava is using the same information  ( distance, elevation) as the Garmin.   But I was honestly surprised to find that the Strava data was pretty darn close to the Garmin/ Powermeter data my guess  is that Strava has loads of data  from all  of the riders that upload their files with power, and that they have created an  algorithm that is far more accurate than the one used by Garmin.  Yea big data!   Strava probably has more information about riders and rides than any organization anywhere and they are really doing some interesting things with it.

Total Calories burned according to Strava: NA

The Strava app  didn't actually give Calories, but it did an amazing job estimating total KJ.  if we know the KJ, we can  do a pretty good job estimating our Calories, as long as we don't make the  KJ=Calories mistake.

Difference in KJ from the Garmin/Powermeter: ~2%

strava calories

So what can we learn here?   Basically we’ve learned that Garmin data on Calorie count is practically useless, without a  powermeter.     The Garmin/Powermeter data does a pretty good job, but still underestimates Calorie count by ~15% ( get on this Garmin engineers!), and Strava did a surprisingly good job with KJ,  but the app doesn't actually give us Calories.     I would like to upload a few more files and see if I get a similar result.    I’m not sure what happens when you upload a  Garmin file (no power) that has a calorie count.   Does Strava use the Calorie count from the Garmin or  does it still only estimate KJ?    Let me know if you’ve experimented with this.


Why do I use Calorie with an upper case rather than calorie with a lower case?  The simple explanation is that 1 “food Calorie”  is equal to 1000 “physics calories.


Thanks again to Jose Areta for inspiring this post.

Great SRM Deal with the new PC8!

Wow, this is a really great deal we are authorized to offer through SRM, and many people will find this too good to pass up.   Its pretty simple, you get a new Dura Ace SRM training system for only $2995.  It comes with a PC7 and a voucher to upgrade to the PC8 at no cost when it comes out in December.  That is a pretty cool deal if you ask me!     Just conact Coach Burke: Sean@CrankCycling.com,  or call us at 619-865-3389 and he'll get you started on your new SRM! Amazing SRM Deal

How To Use a Training Diary, or Keeping Track of the Important Stuff!

Most professional and top amateur athletes keep a training diary.

Training diaries are used to keep record of your training rides and races to track your progress over long periods of time. As a coach I have all my athletes keep a training diary. When filling out a training diary, it is important to record both subjective and objective data. You will also need some way to keep track of training metrics. With some performance testing, discipline, and a diary tracking your training, you can achieve those all-important long term gains in your cycling.

Subjective Data:

Subjective data is information about how you felt during a particular effort or training session. When recording your efforts, make sure to give detailed information about how each effort felt to you as well as how long your efforts were. How you feel is not just important on days when you do hard intervals: it’s equally important on your easy, recovery days. ‘Grade’ your workouts in order to track your progress. I like to use the traditional ‘A’ through ‘F’ scale with plus or minus indications on each grade if applicable.

Objective Data:

Objective measurements or ‘metrics’ are critical to record in your training diary. There are more than a few types of metrics to use when keeping records of your training activities. The coaches at Crank Cycling use Training Peaks software to record metrics with their athletes. Using metrics that give you specific data points like watts from a power meter or heart rate from heart rate monitors are best. Most power meters and heart rate monitors come with a software program to upload your data files for analysis. These are certainly not the only kinds of metrics available, but they are the most reliable. Here are four metrics that I use with my clients and a brief explanation of how they work.

Heart Rate is one of the older metrics available and there’s quite a bit of information about it out there in books, cycling magazines and on the internet. Because heart rate can be influenced by many variables (atmospheric temperature, stress, sleeping habits and diet, for instance) this metric has some inherent limits that will affect and limit reliability.

Wattage measured by a power meter is not new to cycling but power meters have become super reliable in the last few years. They’re inexpensive enough that even a beginning cycling enthusiast can afford one and use it with ease. Power meters have strain gauges in them that measure the force and torque (the power that the cyclist applies with their legs) in order to calculate the wattage being produced. The use of a power meter is one of the most accurate ways to measure a cyclist’s progress.

Speed and Duration can show you how fast you’ve gone on a specific course or how much endurance you have built as your workout times increase. If one of my cyclists chooses to use a heart rate monitor, I always make sure to use speed and duration along with heart rate data.

RPE-Rate of Perceived Exertion is usually represented on a 1-10 scale, 1 being an easy walk and 10 being the most physical exertion you can endure for 10 to 15 seconds. RPE scales seem to work well for riders who are in tune with their bodies and who enjoy pushing their limits. Riders who do well with RPE usually find objective data unhelpful when riding, training, and racing. They might put black tape over their computer’s head unit during training and have their coach look at the actual metrics at a later time. RPE is, of course, considered a subjective metric.

Performance Testing:

Testing yourself on the same course every 3 months to see if you have improved your performance is important to overall, long-term improvement. Make sure you take tests and record them a minimum of 3-4 times a year. Be careful to record test results in your training diary, as they will show your improvement over time. In my next blog post I’ll talk more about the types of tests you can perform.

Tracking Long Term Gains:

Your subjective feedback (how you felt during the training session), and the objective data (your heart rate, watts, speed, and duration of the session) will help give you a picture of how you are progressing. If you keep good records, you will be able to look back at past years and find out what has worked best for you over time. You will also be able to see long-term trends which will help you focus your efforts on what you are making the most gains in.


Set yourself up for success! Create realistic habits for filling out your diary on a daily basis. Make sure that the act of filling out the diary is something that you can realistically do, at a certain time, every day. For instance, if you don’t have time to fill out your diary in the evening don’t plan on doing it then. Plan to do it when you know you’ll have the time and are free to take advantage of that time like just after your ride or during a post ride snack. Attach the chore to something you’re doing already so you’ll never forget to do it!

I try to download my power/heart rate data just after my workout if possible. I write down how my legs felt before the start of my workout, after my warm-up, and how they felt during each repetition of efforts, and then grade myself (A+ through F-).

Filling out a diary will help you make sure that you’re staying on track with your training. If you need help designing a training plan for your next big ride or event, let us know: we’re experts at it and we’ll be glad to help!


Percieved exertion 10 point scale and how to use it.

About 2/3 of the athletes I coach  use power meters to train, and the majority of them use heart rate monitors as well.  But even with athletes that use all of this fancy equipment, sometimes a  "Rate of Perceived  Exertion" (RPE) scale  is the best way to explain  the subjective  intensity of the workout.       This a basically  how hard  you are going on your own personal 1-10 scale.   While  the scale is 100% subjective, it winds up being quite reliable, and has been validated in multiple scientific  studies. ( you can do a Google Scholar search for GAV Borg or Gunnar Borg) The scale is typically given like this:

  • 0 - Nothing at all
  • 1 - Very light
  • 2 - Fairly light
  • 3 - Moderate
  • 4 - Some what hard
  • 5 - Hard
  • 6
  • 7 - Very hard
  • 8
  • 9
  • 10 - Very, very hard

But I also sometimes explain it like this:

  • 0 - Nothing at all
  • 1-2  Super easy, like a slow walk
  • 3-4 Moderate effort, you  aren't going easy anymore, but you can hold this for a long time
  • 5-6 Hard  holding this for an extended period is difficult,  at or just below   race pace
  • 7 -8 Very hard     race pace, as  you can only hold this for a couple of minutes
  • 9 Almost as hard as you could possibly go
  • 10 - This is as hard as you've ever gone your entire life, like someone is chasing you with a cattle prod.

This is  useful for large groups of people such as stationary  cycling classes ( such as the classes I teach at the  Navy and VA hospitals), or situations where athletes don't have have access to, or don't want to use devices such as power meters  or heart rate monitors.  It is also     frequently  use the RPE scale even with athletes that DO use these training devices.   The fact is, that an athlete needs to know  how to go off of feel,  to gauge their own physiological  responses,  just get a  handle on  what they can do,  and when they need to do it.      Don't get me wrong.  I love training, coaching, and racing with power.   But if you you don't know and  understand what  your boy is doing at the moment, and what you are capable of on a purely primal level.   You'll never really reach your maximum potential.

I love my PowerTap, but this is ridiculous.

I saw this story on Velonews today:   Upcoming from CycleOps: Heart-rate-based power meters and superlight carbon wheelset I am going to say this as clearly and simply as I possibly can.  There is no way to measure power using heart rate.   It just isn't possible.   Heart rate is to dynamic.  It changes due to factors such as fed state, level of fatigue, how long you have been exercising, hyrdation level and more.      Power measured via strain gauges is instantaneous,  and any effort put into the pedals can be measured right then and there, but but  heart rate may take several minutes to catch up.    So heart rate is a reasonable proxy  for effort level on long efforts, but  is practically useless for long efforts.

Like I said, I love my powertap,   I have one on my bike, and I have a studio full of powertap stationary trainers.   But don't tell us you are measuring power when you aren't.    What PT is trying to do is measure training stress using heart rate, and make it applicable across different types of exercise.   This is nothing new and it can be useful.    You can read a good article on TRIMP HERE.    But there is absolutely  no no way that TRIMP equals power measurement.


New Warm Ups Posted for Road, Mountain, Cross, and Track

A warm up is an important part of your race preparations.   It  is rather silly to  train for countless hours,  travel to a race, and payg entry fees if  you aren't  going to be properly warmed up. A  proper warm up may not necessarily  win  you the race, but it can definitely lead to a sub-optimal performance and can lose you the race.   We have posted  warm ups for road racing, cyclocross racing, crit racing, time trialing, track racing, and mountain bike racing.    These warm ups are not set in stone, and you may have to experiment a little bit to find out what works best  for you.    If you haven't been doing a structured warm up, or are looking for something new, consider them a starting point.   If you like them, stick with them,  but  feel free to experiment a little.     You'll more find  information   links to all of our warm up  protocols here.

Is power measurement the "End All Be All?"

I personally have been using power meters since 2002, and I love to use power meters to coach athletes. I'm kind of a science geek and I love to crunch the numbers and evaluate the data. I also love that fact that the power data can enhance or even tell a different story from what the athlete conveys. Power meters give truly objective and accurate information that can't be obtained any other way. They let us track progress more accurately than any other method, and they help us dial in an athlete's effort level to ensure an efficient use of time, as well as determine when "enough is enough." There plenty of resources out there on training with power, and there is ever more powerful software available to analyze, evaluate, and plan training. These are all powerful tools, that help athletes track and attain higher levels of fitnes, as well as help coaches communicate and track their athletes better than ever. The problem comes when athletes and coaches become too reliant on the power meter.

The training and coaching of an athlete is not just a simple recipe or formula with predetermined inputs and outputs. Every athlete is different, and every athlete's response is going to be just a little bit different. An athlete needs to be viewed as a whole organism, not just a set of power data. In fact the subjective feedback from an athlete is every bit as important as that power data. I think some athletes and coaches easily forget that. They just want to open up a book, take training plan from the book, and adjust it for the athlete's power numbers. It is easy to get caught up in all the charts, graphs, and information that today's powerful software provides, but all those charts and graphs just don't tell the whole picture. I would argue that power data in isolation can even confuse the issue. For example in riders look at their power meter data along with a chart that says they are in a Cat 1 range and get frustrated because they are still a Cat 3.

How and athlete "feels" is every bit as important as what that athlete does. In fact there are several athletes I have been training for years that don't use a a power meter, a heart rate monitor, or any piece of electronic equipment on their bikes whatsoever. We train primarily using RPE (Rate of Perceived Exertion), or how an effort feels, and these athlete have reached many of their goals, as well as put wins on their palmares. Power meters have their place. And if i had my way, most of my athletes would train and race on them all the time. But power meters aren't for everyone. Price, functionality, and even all of that information makes powermeters and training with power undesirable for some.

For those that don't want to train with power, RPE works just fine. I used to rely heavily on heart rate monitors for athletes without power meters, but now I've gone the other way and prefer to use just mostly RPE. Heart rate data can simply change so much from day to day, and RPE conveys both what I want from the athlete, as well as what the athlete should do much better than heart rate.

Power meters have their place and many coaches and athletes love to use them, but they are by no means a requirement for success. Coaching and training is more than just looking at power numbers, and the entire experience of the athlete needs to be taken into account. Rate of perceived exertion and how an athlete feels is just as important as power numbers, and many coached athletes are successful using nothing more than than their own perceptions and some feedback from their coach.

Use the comments section below to tell me what you think.

"Understanding Your Power Files" Clinic

Ok, You've got this fancy doohicky on your bike. Maybe its made in Germany, maybe its built in the US, . This fancy thingamajig may have cost you just about as much as some people spend on their entire first racing bike. It tells you how hard you are going in watts, it tells you you average watts, your max watts, it tells you how much work you've done in kiljoules, and more. It gives you all sorts of information, but what do you DO with all this information. The coaches at Crank Cycling are here to help. We work with power every single day. We sell more Power Tap and SRM power measuring systems than most bike shops. We've helped elite athletes analyze their power files, and adjust their training.  We've written articles on power for local and national cycling news outlets, and we want to share our knowledge with you with you.

This clinic will cover:

  • The basics such as how power is measured, what are the advantages and disadvantages of the different power measuring systems.
  • How, when and why you should do field testing with your power meter.
  • How to monitor and analyze individual workouts as well as weeks, months, or years worth of data.
  • Creating and implementing a training plan based on power.
  • Racing with your Power Meter
  • and more

This clinic is appropriate for anyone who owns a power meter, or anyone who is thinking about purchasing a power meter.    It is appropriate for self coached athletes as well as athletes who work with a coach (Crank Cycling or anyone else!)*.    Knowledge is power, and the more knowledge you have, the greater your chances for success.

The clinic is scheduled for Sunday November 20th at 1PM at our downtown training studio and is expected to be 3-4 hours in length.   The cost of the clinic is $99 with discounts being offered to Crank Cycling coached athletes or clubs with more  5 than athletes attending.

Registration is HERE , or use the contact form on the lower right or call Coach Burke at   six- one –nine -865-3389 for more information.

*Athletes that work with another coach may bring their coach with them to the clinic for no charge.  We welcome the company of knowledgeable coaches, and encourage their  participation in the question and answer portions of the clinic.