Archive for May, 2010

The 600k trip to Hell and back

| May 24, 2010 11:23 pm

by Chuck Schroyer

The event started much the same as the 200k and the 300k leaving from the Golden gate in the wee early morning. This 6pm start was in the daylight without rain, this was a good sign. Art Cruz had asked if we could ride together because he had never done a Brevet out of San Francisco and the cue sheets had a lot of turns that could get him lost. Not haven ridden with Art in a number of years I was a little concerned about our possible different riding styles.

The ride started right on time and soon we were able to settle down, once you are on the bike many of the worries seem to go away. The ride out to the first checkpoint 2 Point Reyes Station was cold but nothing we had not prepared for, things were looking good. After a great Chocolate bread pudding that was just out of the oven, I knew I was in heaven, things could not be better riding and eating life was wonderful. I was right things would not get better, soon we started to get the jest of the ride, rolling hills and a constant headwind and I say that with a capital H.

Art and I found that we rode well together and grouped together with other riders during the more winder portions of the ride. The next checkpoint 3 was Peet’s coffee in Petaluma, things were still going well and the Latte with heaps of sugar hit the spot, on to checkpoint 4. We were starting to get a little tired of the rollers and the headwind they seem to sap the strength. Checkpoint 4 was in Healdsburg and it was getting late in the day so there was no soup at Safeway something my mind was hoping for the last few miles. I was able to make up for the lack of soup with a great croissant chicken salad sandwich.

The fun Begins!

Coming out of Healdsburg you go up to Cloverdale where the climbing begins, not like the rollers are actually climbs. Art and I were riding with a group of six when we started the climb, although it was only a 1300ft climb the grade wore you down. I was the first to the top and was feeling good the rest did not fare as well; the blood was running from the wounds of those that overlap wheels on a slow climb, nothing fatal just more battle scars. The run out to Checkpoint 5 proved be harder than expected, 93 miles between checkpoints and the sun going down. The ride support people had set up a bag drop about 30 miles from Ft Bragg and it was a God sent. Something to eat some extra water and the adding of lights and we were off for Fort Bragg, well after some messing with my rear derailleur, things not shifting right.

Wind is howling coming into Ft Bragg around 10pm temperature around freezing and can’t get worm. After putting on two polypro under layers arm warmers and two jackets I decide it is too cold to ride on. Thanks to Art and six plastic bags and one large paper bag under my jersey I was ready to go.

After messing with my rear derailleur again we were off, much in hopes of finally getting to ride with the wind and not into it. 181 miles of headwind was enough for me. We made it back to the Bag drop and were greeted buy some of the greatest volunteers ever, hot bean soup “yes I finally got my soup” and hot Chocolate and best of all and roaring fire. It soon became apparent I was toast I had thrown up everything I ate at Ft Bragg and the soup looked like it would have the same fate. Art was ready to ride and we had 50 miles to Cloverdale to a Hotel we reserved for the night. Think time line here it was 2pm and it had taken us 4 hours to do the 50 miles from Cloverdale. We said our good bye and Art road off in the freezing weather a better man than me. One of the volunteers’ must have felt sorry for me because he offered me his tent and sleeping bag. I closed my eyes only to be awakened by the volunteer telling me it was 4pm time to ride “what the f@*k” I obeyed my commander and got back on the bike, after playing with the derailleur.

No tail wind and bitter cold I was praying for a climb to heat up the body, why is it that it seems to be the only flat 14 mile stretch in the whole ride in front of me. Shifter not working very well only have my two climbing gears but still have the front chain rings, thank God I have a large spread a 34 and a 54, and this will be the saving factor for the whole ride.

Watching the sun rise was glorious but the ride back to Cloverdale became a daunting task, one large climb and rollers that never seem to end. Coming into Cloverdale and seeing other riders made my day. The stomach was not altogether right but ordered pancakes and eggs anyway, got about one third down and felt better. Surprises never cease here pulls up Klay Cardona he had got 5 hours sleep and left an hour and a half after me from the bag drop and made the cutoff at Cloverdale with 15 minutes to spare.

Feeling better and the wind at our backs Kley and I dropped the hammer and make the run to checkpoint 6 Guerneville. We make it there with an hour and fifteen minutes under the cutoff, things were looking up. Still had the shifting problem and again messed with the derailleur this time deciding to oil the cable housing with sun screen, this did not work for when I pulled on the cable it broke in two. It had broken inside the shifter “not good”. Kley and I looked for a bike shop to no avail. I finally just pulled it up tight so that my rear derailleur was on a middle gear and tied it off. We were off; on the flats I would spin above 100 to keep up, using the 54, and grind out the hills with the 34 my life saver.

Pulling into checkpoint 8 brought another surprise there was Art, we got to hear Arts tale of sleeping on the concrete floor of some post office, he did make to hotel in time to shower before checkout. We made a pack to finish this thing together for without each other we would not be here. After tightening my derailleur cable some more to get me into a better climbing range we headed out of Point Reyes station to the finish. With the lower range I could not keep up on the downwind legs, I have to give it to the fixed gear people they are nuts. Only four climbs left with the lower gear I could grind out without walking but knew that the last climb up to the Golden gate would do me in.

At last climb, I talked Art and Kley to go on ahead because I would most likely walk most of it. Pulling the derailleur cable up as hard as I could I was able to get almost all the way up to my climbing gear. I was determined I was going to make it. Coming around the last part of the climb before you cross the road and cross the Golden Gate there was Art and Kley not willing to cross without me, a perfect ending to the most grueling rides I have ever done.

We hit the checkpoint finish line at 8:13pm and all got the same time, 36 hours and 13 minutes.

The rollers added up to 23,342 ft of climbing, total distance 375 miles, knocked off the bike twice by the wind. This was a once in a lifetime experience that has taken me as close to the edge as I would ever wish to get.

Courses on the Garmin Edge 500

| 9:50 am

Once point of confusion when people are deciding between the Garmin Edge 500 and 705, is the lack of maps on the 500. Some come to the conclusion that the Edge 500 provides no navigational features, which is not true.  Although you can not get a street level view, with the pre-plotted course shown, you can upload courses from either an existing workout or by mapping them in advance. You add the course in the Garmin Training Center program and then send it to your Edge 500.

After transferring the course to your Edge 500, select Training from the Menu, then select Courses

Next select the course file you wish to use.

Your Garmin now has three additional screens.

The first one shows the hill profile behind and ahead of you.  This is quite useful as you are making a long climb since you get a visual clue of the grade ahead.

The nextr screen which I use primarily is the course on a simplistic map.  You can use this to navigate you way along the course.

The arrow shows where you are and the line shows what is ahead.   If you look at the screen above, it is easy enough to see you bend to the left and then a right turn is coming.  The course keeps getting updated as you move along so you can tell you are getting close to the turn.  At the top of the screen, once you are on the course, it will show the total distance to the end of the course.  If you get off course, you will receive a warning message.  Even if you are off course, but near the course, you can see your location by the pointer and the course line off to the side, and easily find your way back.

The third new screen is only there if you take the time to enter course points in Garmin Training Center.  This involves entered every turn, picking an icon to show left, right, summitt, etc, and the name of the road you turn on.  You then get a live, constantly updated route sheet.

One problem I have noted is with an out and back course.  If you did not go fully to what it thinks is the turn around point, on the way back, it seems to think you are off course and wants you to return to the turn around, but the line still shows and you can follow it back.  It is just annoying to have it flash “off course”, then “found course”, repeatedly.

Training Log Online Options

| May 12, 2010 9:00 am
Training Log Online Options

by Franz Kelsch with contributions by Steve Saeedi – last updated: May 12, 2010

Years ago, as runners and cyclists, we would sometimes keep a training log in a notebook, or maybe one of those free booklets that Runner’s World magazine gave free if you renewed. I started to keep my workouts in an Excel spreadsheet, which I keep up through today. Computer based programs were released and as manufactures starting to sell devices which provided for data upload, they usually included some program to work with their device.

There has been a recent explosion in the number of websites that allow you to track your workouts online. With the growing popularity of GPS enabled devices for cycling and running, most of these sites allow you to upload your workout directly from the device, making the process much simpler. Why would someone use a web based approach to a training log? There are a several of key advantages to using a web based program. First it is device independent. To this day, Polar still has not released a Mac version of their training program. Some programs have been released only on a Mac. None of these work on mobile devices, such as smart phones. All these limitations are solved by using a web based approach.

There is the additional advantage with the movement to social networks. If I put my workout in my own log, it is not visible to anyone else. With the web based options discussed here, you can share those with your friends who are using the same web based application, over social networks such as Facebook and Twitter, and embed code inside your own blogs and websites. The social aspect is enhanced with many of these sites offering a Leader board so you can compare your training with your friends or even all users of that site.

Just a couple of years ago web applications were very limited. That has changed significantly and some of the best web based applications, such as Strava, using Ajax features to give you the feel you are using a local based program. In addition, most all of the web applications are free to use, funded by advertising. So is there any downside to using a web based application? The answer is yes and it is common to the movement to the cloud for both data and applications. Your data is stored somewhere else. It is often impossible to export it out. If the site shuts down then you have lost all your data. So you may wish to keep a local copy of the data using the program that came with your device. My Excel spreadsheet has lasted for well over 10 years, as technology has come and gone.

We are looking at the following web based applications. This is not an all inclusive list, but does include many of the popular sites that allow tracking of workouts.

  • Garmin Connect – A free only site geared to those using Garmin GPS devices but does allow manual input .  Also allows for GPX update of Garmin and non-Garmin workouts. Also provides elevation correction for devices that don’t have elevation or barometric altimeters. Can export activities in any number of formats.
  • Strava – A subscription only site that allows GPS upload and manual that automatically shows how you are doing compared with other users climbing the same hills.  For devices that don’t have power meters, Strava will calculate and chart wattage for devices that have barometric altimeters. Cannot export activities.  They recently released an iPhone application.
  • Plus 3 Network – A free site that allows both GPS upload and manual input.  It has a unique aspect that let’s you earn money for your selected cause, based on your miles.  Each of the optional causes has a sponsor who pays the money.  You earn money based on your miles and/or time depending on type of workout. Cannot export activities.  They have an iPhone application.
  • Daily Mile – A free site that is more geared to runners. Allows both GPS upload and manual input.  A Facebook type social network approach to sharing your workouts.  Cannot export activities.
  • Training Peaks – A free site, with premium option, that allows GPS upload and manual input.  Some very detailed analysis tools.  You can print workouts but not export the data.
  • Ride With GPS – A free only site (provision for donations).  Excellent mapping tools.  Allows upload of GPS files for plotting courses and downloaded of courses to GPS devices.  For devices that don’t have power meters, the site will calculate and chart wattage for devices that have barometric altimeters. You can export individual workouts in a number of formats.
  • Map My Ride and Map My Run – Free sites, with various premium options.  Geared toward those who wish to map out their running and cycling courses that can be downloaded to GPS devices.   They do support upload of workout information but do not support uploading from a Garmin Edge 500.   Heavy advertising on free sites is intentionally annoying to encourage you to pay for on of the premium options.  They provide iPhone applications (both free and paid) that allow you to use the iPhone’s GPS to track your route and upload it.

Below is a summary table followed by a detailed review for each site with many screen shots included.

Web Based Training Logs

Website Site Garmin GPS Suport Polar HRM Support Allows Export Price Social Network Estimates Power Tracks Gear Map Drawing Exports to Device iPhone Android Support
Garmin Connect Yes No Yes Free Good No No No Yes No
Strava Yes No No Paid Good Yes Yes No No Partial
Plus 3 Network Yes No No Free Poor No No No No Yes
Daily Mile Limited No No Free Excellent No Yes No No No
Training Peaks Yes Yes No Free/Paid Good No Yes No No No
Ride with GPS Yes No Yes Free Good Yes No Yes Yes No
MapMyRide Limited No Yes Free/Paid Good No Yes Yes Yes Yes

Garmin Connect

If you connect a Garmin device to your computer (either Mac or PC), and click Upload, the workouts are automatically sent to Garmain Connect.  The map of the course and workout details are shown.  You can view the data by splits and also on some of the included graphs.

There is a player option that shows your workout parameters as the pointer moves along the course.  You can easily share your workout on Facebook and get some code to embed the workout in a website or blog.

You can search for other posted routes in your area and download the route to your Garmin device.  There is a nice calendar view that makes it easy to find a particular workout.  It shows the total miles per week, but it adds cycling and running miles together.  There is not tracking of miles on a year to date basis.

The data closely matches the input from the Garmin device, including your split times, calorie estimate and distances.

Strava

This is the only site being reviewed that has no free option, which will make it not an option for many users.  It accommodates other types of workouts but is best suited for cycling.  At this point, it is the only site, other than Garmin Connect,  that will upload Garmin Edge 500 files by simply clicking Upload.  Other sites require browsing to the FIT file or do not support the Garmin Edge 500, one of the newer Garmin devices.

If you drag the pointer along the elevation profile at the bottom, it will show you location on the map and some of your key data at that point in the workout below the map.   This site has a Leaderboard that ranks all users on a week to date based on such things as miles and climbing.  One of the unique features is it will use the uploaded GPS data to see that you climbed a particular hill and show how you compare with others who did the same climb, and provide for an automatic KOM listing.  Below shows the ranking in Strava for the Metcalf climb (in California).

There is also a map for the hill climb and if you run the pointer along the profile, it shows where you are at that point in time compared with the KOM leader.

It is easy to share your workout with Facebook. The site will estimate your power output along the course, unique amongst all the sites reviewed.  You can get graphs for the whole ride or for a particular split.

There is a unique calendar view, with a graph of  miles for each day, with a link to the workouts that day, making it easy to find a particular workout.  It shows your total miles, but adds running and cycling miles together.

You can track which bike you are riding, but beyond that there is no way to track equipment usage.  Strava users can join clubs and see how they are doing with other club members.  You can also have selected Friends.

A unique aspect of Strava is it’s estimate of average power output for the entire ride, or one segment, such as a climb.  Another nice feature is to find local routes, climbs and other athletes.  This could be of great value to someone cycling in an area they are not familiar with.

Plus 3 Network

This site is unique in that it now only allows you to upload your workout, but has a sponsor/cause system so you earn money for your selected clause, paid by the sponsor.

As you do any activity (run, cycle, walk, even volunteer time), you get earn “Kudos”, and therefore more money for your cause.  If you upload a GPS file instead of manually inputting your workout you get more Kudos per mile.  The site does have some graphs for your workout, but only for the entire workout and not by split.  It offers a calendar view of your workouts, but there is not a good way for you to see such things as your accumulated miles over the year or month.  It adds all miles together, regardless of the type of sport.

The site supports some social network features.  You can request another user to be your “friend”.  The site provides a leader board that starts each month and shows how many “Kudos” each person has earned.  You can compare yourself against your friends or everyone on the site.

The social network features are limited and it is not easy to post your network to Facebook.

Daily Mile

When you enter the site you feel you might have entered into Facebook by mistake.  The site is heavily oriented toward social networking.  Many people (including myself) post a lot of work out information on Facebook, but having a site dedicated to those who really might be interested could be useful.

The site offers good tools for showing your miles per week, month and for the year.  They have a calendar view to find your workouts.

There is a leaderboard where you can compare yourself with just your friends, or all users of the site.

The site provides for GPS upload but does not currently support the Garmin Edge 500, so I have been unable to test the mapping features.  You an attach gear, such as running shoes, or a particular bicycle to each workout and then track the mileage on that particular piece of gear.  There is no way to export your workouts.

Training Peaks

Training Peaks probably offers the most features of any of the sites, so many that you can get lost in the site.   It allows you upload GPS data (including browsing to Garmin Edge 500 FIT files) and manul input.   It also allows uploading of Polar HRM files, one of the few websites that supports this.  There are three main views of your workouts, Calendar, Spreadsheet and Dashboard.

The dashboard allows you to add “pods” and track nutrition.  The site allows you to view your data over many different data ranges, such as last 28 days, last 14 days, this week last year, last two years and many more.  For those who are interested in how their training is racking up, this is an excellent site.  It is also the only site that makes it easy to see how  much of your effort is between different sports, while most sites just add all miles together.

There is a very detailed map and graph view.  The graph is very detailed, almost too much so.

You can easily share your workout with others, such as Facebook.  It will even create a shortened URL to use.   You can attach gear, such as running shoes and bicycles to workouts and then track the mileage on that gear.  There is no way to export your data, other than to print it.  I did not evaluate the Premium options because the costs for premium seems to high for post users.

Ride with GPS

This is a free site with excellent mapping tools but none of the annoying advertising like Map My Ride/Map My Run.  It does ask for donations.  You can view your workouts in table or calendar view.

You can upload data directly from a GPS device, or use their excellent mapping tools to draw the course.  If you draw a course, it will create the turn by turn route sheet, although it has errors at times.  Unlike MayMyRide, everyone an print the route sheet.  It has good provisions for embedding the map in a website or blog.  It is also easy to share your workout on Facebook.  Although you can manually input a workout, it wants to know the route, so this site is not recommended for those who do not have a GPS and don’t want to draw out every route they use.  This is understandable because the site is more oriented to mapping than to tracking workouts.

For your workouts you can view the map, workout data, and some graphs.

It will show your activity totals by week, but combines miles from various sports.  There is no feature to see your miles over the course of a year.

MapMyRide and MapMyRun

This site allows you to draw a map of your course, or upload a Garmin GPS file or Polar HRM file.  It does not currently seem to support the Garmin Edge 500 so I had to export to a TCX file to upload.

The main screen has four sections, nestled in excessive advertising.

This screen capture shows how cluttered the screen can be.  The map of your workout is small compared with the excessive advertising.

If you click on the map from an uploaded GPS file, or one you draw, you get a good map view and a nice profile view at the bottom that shows you the percent grade along the route.

The MapMy series as several iPhone applications that allow you to use the GPS in the phone to track your ride/run/walk and upload via the 3G network to the MapMyRide website.  You can export routes, including the ones you draw, to various formats.  MayMyRide has strong mapping tools and allows you to draw maps even on bike trails, something most mapping websites do not support.  A new Leaderboard is being added.  There is strong support for sharing your information via social networks or embedding some code in a website or blog.

There are three paid options, $30, $60 and $99 a year.  Of all the sites, MapMyRide seems to be the most commercialized, which has some advantages in terms of features, but with the downside of the constant nagging to get you to pay something.

Cycling Power Calculations

| May 2, 2010 12:52 pm

by Franz Kelsch

In another post I wrote about the many cycling power meters that are available to measure in real time the power a cyclists is applying to the pedals. This article provides some of the science behind cycling power and formulas that are being used on the Ultra Cycling website to estimate power for those riders who do not have a power meter. If you are one of the many cyclists who mistakenly say that the effort goes up the the square of the speed, you might want to read this article.

Work, Energy and Power

These terms all mean something different, but are indeed related.  A basic understanding is needed before we move on to discussing Power in cycling.

Work refers to an activity of a force being applied and movement over a distance in the direction of the force.  If you cycle up a hill you are doing Work. The typical unit of the force being applied is newtons.  One newton is equal to the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second per second.

Energy is the capacity to do Work.   The source of energy came come from potential energy, as when descending, or energy produced by your body. The typical unit of measurement is the joule. One joule is the energy exerted by the force of one newton acting to move an object through a distance of one meter. The calorie is a pre-SI metric unit of energy. It is still used for food energy, referred to as Calorie (capital C).  This is called a kg calorie, or 1,000 gram calories. One gram calorie equals approximately 4.2 joules so one Calorie (as in food) equals 4,200 joules, or 4.2 kj.  The body is not that efficient in using the energy in food and only about only 18 to 26 percent of the energy available from respiration is converted into mechanical energy. Considering this efficiency, 1 Calorie of food consumed (4.2 kj energy) can produce 1 kj of energy to the pedals.

Power is the rate of using Energy.  If Energy were money in your pocket, then Power would be how fast you are spending the money and what you bought with your money would be the Work accomplished. The typical unit of Power is the watt.  One watt is equal to 1 joule of energy per second. When we are taking about Power output when cycling, as measured in watts, we are taking about the rate we are expending Energy to moving the bicycle and rider forward (Work).  If the cyclists is applying a power of 100 Watts to the pedals, that means 100 joules per second, or 360 kj per hour. To replace that energy, the cyclists would need to consume about 360 Calories of food per hour.

Forces in Cycling

There are certain forces opposing motion of the bicycle that the rider needs to provide energy to overcome. These forces are:

  • Rolling Resistance. This  is friction from contact with the road. It is affected by the bike quality, tire, road surface, tire pressure and weight of of the ride and bicycle.  At very low speeds, on a flat surface, this is the main force.
  • Air and Wind Resistance.  Air is a fluid (although one with low density) and any object moving through the air will encounter friction. It is a function of the speed of the bike plus the wind speed, the area and shape of the cyclists and bike, and the speed being traveled.
  • Gravity. When climbing the rider needs to put in sufficient energy to “lift” their own body weight plus the weight of the bike. It is is a function of the grade and speed.  As the elevation increases, the potential energy increases.  This potential energy can provide energy back whenever the cyclists descends.

Power is the work required per unit of time to overcoming the net forces acting on the rider and bicycle. If you add each of the above forces and multiple by the speed, the result is the power required. The power is applied by the pedals and equals the force applied to the pedals times the velocity of the pedal movement.

Estimating Power Output

Those interested in the math can read further on how to estimate the power required to overcome each of the forces on the cyclists. These are simplified formulas dealing primarily with static forces and do not take into account all items that affect the forces such as wind, impact of turbulence, mechanical fiction in the drive train, etc.

Rolling Resistance

Terms

  • Frl – Force, in newtons, caused by rolling resistance
  • Prr – Power, in watts, to overcome Frl
  • Crr –  coefficient of rolling resistance – typically 0.004 but can be as high as 0.008 for bad asphalt or as low as 0.001 for a wooden track.
  • g – acceleration due to gravity – 9.8 m/s2
  • Wkg – mass of the ride plus bicycle in kg
  • Vmps – Veloicty in meters/sec

Formulas

  • Frl = Wkg x  g x  Crr
  • Prr = Frl x Vmps

Example

Take a rider and bike combined weight of 165 lbs (75 kg) traveling at traveling at 20  mph ( 8.92 meters per second), using Cff of 0.004 and with g being 9.8 meters/sec/sec.  The force would be:

  • Frl = 75kg x 9.8 m/s2 x 0.004 = 2.94 newtons.
  • Prl = 8.92 m/s x 2.94 newtons = 26 watts

Since the power is proportional to speed, the same rider traveling at 5 mph would require 6.5 watts to overcome rolling resistance.

Air and Wind Resistance:

Terms

  • Fw – Force on rider and bicycle due to wind drag
  • Cw – drag coefficient, typically 0.5
  • Rho – air density in kg/m .  Depends on temperature and  barometric pressure. Some typical values are sea level: 1.226, 1500m: 1.056 and 3000m: 0.905
  • Vmps – Speed in meters/sec
  • A – effective frontal area of the rider and bicycle in m^2.  Typical value is 0.5.

Formulas

  • Fw =  1/2 A Cw Rho Vmps^2
  • Pw = Fw Vmps

Example

Take a rider and bike combined weight of 165 lbs (75 kg) traveling at traveling at 20  mph ( 8.92 meters per second), with no headwind, using Cw of 0.5, Rho of 1.226 and front area of 0.5. The force due to wind drag would be:

  • Fw = 1/2 x 0.5 x 0.5 x 1.226 x 8.92 x 8.92 = 12.19 newtons
  • Pw = 12.19 newtons  x 8.92 m/s  = 108 watts.

If you at traveling at 5 mph, instead of 20 mph then:

  • Pw = (1/2 x 0.5 x 0.5 x 1.226 x 2.23 x 2.23) x 2.23 = 1.7 watts

Gravity:

Terms

  • Fsl – Force in newtons due to the pull of the rider and bicycle down the slope
  • Psl – Power in watts required to overcome the force of Fsl
  • Wkg – Combined weight of the rider and bicycle in kg
  • g – Acceleration due to gravity, 9.8 m/s^2
  • GradHill – gradient of the hill, in decimal, the ratio of the rise to the horizontal run.

Formulas

  • Fsl = Wkg x g x GradHill
  • Psl = Fsl x Vmps

Example

Take a rider and bike combined weight of 165 lbs (75 kg) traveling at traveling at 5  mph ( 2.23 meters per second), climbing a hill with a grade of 12% (GradHill = 0.12).  The force due to gravity would be:

  • Fsl = 75 x 9.8 x 0.12 = 88.2 newtons
  • Psl = 88.2 x 2.23 = 196 watts.

Combined Forces

Formula

  • Total Power = Prl + Pw + Psl   or Total Power = (Frl + Fw + Fsl) x Vmps

Examples

Using the values we already calculated in the above examples:

  • Flat Road, 20 mph:  Total Power = 26 +108 = 134 watts.  Here most of the power is used to overcome air drag
  • Flat Road, 5 mph: Total Power = 6.5 + 1.7 = 8.2 watts.  Here most of the power is used to overcome rolling resistance
  • Climb, 5 mph, 12% grade: Total Power = 6.5 + 1.7 + 196 = 204 watts.  Here most of the power is used to overcome gravity.

Some cyclists mistakenly say the power needed goes up by the square of the speed. Although the force due to air drag goes up by the square of the speed, the power required due to air drag goes up by the cube the cube of the speed.  Speed has a linear impact on rolling resistance force and no impact on gravitational forces.  Remember to get power we multiple the force by the speed.  Air drag forces already have the square of the speed in the formula so to get power your multiple by speed once again.

Real World

The above calculations are based on a simplistic model and exclude the effect of wind and some other dynamic forces.   Wind is very seldom zero and even on a circular course there is net loss of power due to wind, assuming wind is constant. There are also factors influenced by aerodynamics of the type of clothing being worn, the type of helmet, the biking position, turbulence caused as the air flows past the rider.  Except in the case of a tail wind, all these other factors will increase the power required. For climbing significant grades these additional factors are small compared with gravity and can be ignored.  However for flatter terrain at high speeds, some additional watts or power output will usually be measured.


References: