Hills Are Easy - The Science of Pacing, Using Gears and Bike Set-up

Below is a short piece I've written on riding hills.   It was hard to place limits on the topic without going to to 2 or 3 other discussions. I apologize for any grammar mistakes.  I'm heading out of town this afternoon and wanted to wrap this up before I left. Enjoy!  Feel free to ask any questions.

Hills Are Easy – The Science of Pacing, Using Gears and Bike Set-up

By Coach Mike Girard - 11/23/14

I frequently see the comment among athletes that a particular race course is hard because it’s so hilly.  They typically go on to recommend practice tons of hills in training.  I’m not going to say that’s a bad thing.  Not at all.  Variations in terrain or wind are always good opportunities in training.   However, many athletes view these challenges as well, very challenging.  Using the proper equipment selection and pacing plan, it’s possible to make hills or wind no more challenging that a flat open segment of roadway.

To understand how a hill or wind are different than a flat road on a windless day.  First we need to review the opposing forces that determine how fast you are traveling.  From the moment you bicycle starts rolling, you are balancing both drag slowing you down and the power generated pedaling.  If the force produced exceeds drag, you accelerate.  If the force is less, you decelerate.  If equal, your speed stays constant.   SO what forces are slowing you down or potentially speeding you up in some cases?   There are 3 primary forces (we’ll ignore drivetrain losses for now). 

1)      Wind Drag – This is how efficiently you push a hole through the air as you move forward.   For practical purposes, wind drag is insignificant below 10-12mph or relative air speed (not ground speed).  Above 12mph, this is the primary force slowing your down.  Wind drag if impacted by wind.  To reduce this force, you need a more aerodynamic position, or use equipment that is more aerodynamic.   With aerodynamics, the shape and location of an object is often more important than its total size.  EVERY OBJECT on a bicycle impacts your drag, and one object can influence another.  Very, very small changes in shape or texture can have a large impact.  The ideal aero position would make a bicycle impossible to ride, control, is uncomfortable, to is illegal based on the rules of sport.  So your position is a compromise of comfort, ability to make power and safely handle the bicycle.

2)      Elevation gain (or loss) – More specifically, you are storing or recovering potential energy.  A hill is like having a battery on your bicycle, except you don’t get to control when it’s charging or releasing energy.  You can control how quickly it’s stored in how fast you go up a hill.   The rate at which you go uphill is determined by your total weight and the power output.   When you go downhill, the opposite occurs, but because speeds are higher #1 becomes a factor.   To reduce this force, you ride slower.

3)      Rolling resistance – the drag created by your tires as they roll.   The primary drag is caused not by the tire & road interface, but by the tire casing (sidewalls) flexing as the wheels spins.  To minimize drag, you can select tires and tubes that are more flexible.  However, very flexible tires are more suspect to cuts and punctures, so you must compromise.  Additionally, you need to select the optimal air pressure for the road surface and rider weight.   Higher pressure can be slower than lower pressure.  Also wider tires typically roll better than narrow ones, but have more wind drag.

On the opposite side, of the equation, a bicycle is propelled by the rider generating force (torque) at a certain frequency (cadence… revolutions per minute (RPM)).  These combined are the power a rider is making.  Muscle are contracted and your cardiovascular system supplies the muscles with fuel and oxygen.  Over a period of time, muscle become fatigued.  How these systems interact to allow this to happen at different power levels is another topic, but it’s directly related to pacing.   

The power is then transmitted through the drivetrain.   The gear ratio selected will determine what RPM you are riding at.  This will determine the amount of force vs. frequency needed for a given power level.  The range of gearing on a bicycle needs to reflect the maximum and minimum speeds you expect to ride at a given power level.  This doesn't need to be emotional or complicated.  If you want a minimum of 80RPM, and your power level indicates 5mph at you weight climbing a grade, then you need to correct gear ratio to accomplish this.  There are several websites that will allow you to calculate gear ratios for a given speed. This could mean using a different range of gears up front or triple chain ring to have the correct gears. 

My daughter just demanded that she type her name…. her name is Brielle.  Sorry about that.

So why does a hill feel different than a flat road.  The reason for this is the same reason most indoor trainers feel different than riding outdoors.  In fact both hills and in indoor trainer are very similar.   The first is that you are moving slower and therefor have less inertia or in other words the stored energy determined by the weight of the bicycle and rotating mass of the wheels. The result is that when you are pedaling, you pedal stroke is less smooth since you decelerate more between the most powerful parts of you pedal stroke.   This is more noticeable the lower your cadence and will have a small influence on which muscles are used more when pedaling. The second is that you have less air moving over you, so you feel hotter, which can make riding harder, or at least feel harder.  Finally, a rider may sit in a different position.  This too will engage slightly different muscles more than others.

When it comes to racing an individual time trial or bike leg of a triathlon, you time split is most closely related to your average power or in other terms, your total energy output. 

It sounds obvious, but too commonly riders are trying to maintain a given speed during a race.  In reality, you should completely ignore speed, and maintain the ideal power during the event.  For the moment, we’ll ignore special situation such as race tactics, legal drafting or pacing out of T1 due to the stress of swimming.  The ideal power level when going uphill or downhill should be only slightly harder or easier than a flat road without a headwind or tailwind.

How can you determine the optimum power level for bike leg or race?  The easiest way is to use a tool such as the website BestBikeSplit.com.  The details of how to utilize this tool is another long topic altogether.  But what you can get out of this tool are power targets for different situations and the associated speed given your ability and equipment selection, which will give you the fastest bike split.   If you rider harder or easier than the pacing plan, you will go slower. 

Putting this together, a rider only needs to know how hard they can ride based on their training & fitness, choose the correct gearing for the course and conditions and execute their pacing plan by shifting their gears to maintain an ideal RPM at a given power output.  The rider needs to resist the temptation to ride harder than planned as they slow down due to conditions or how others are riding around them.  While this will take practice to use good discipline when riding, physically, the training stress of riding actual hills is not necessary and can be counterproductive in an overall training plan in some cases.  You goal, should always be to build fitness by creating the most adaptation possible, while still having fun while being challenged and staying mentally engaged.