Archive:
Ride Smart / Not Hard
Today's Topic: Human Efficiency
By Peter Jensen
In the last edition of "Ride Smart, Not Hard," (archive) we concluded with the statement: "…don't waste energy compressing or stretching the crank arm. Instead, make circles with your feet." This is a specific statement within the very broad subject of efficiency, which is important in virtually every process, both natural and man-made. From light bulbs, to microwave ovens, rocket engines, automobiles, and the conversion of corn into dairy products, efficiency invariably affects both the process and the outcome.
If a cow produces an unusually large volume of milk relative to the feed it consumes, then it is an efficient and desirable cow. If a new engine design increases the gas mileage of your SUV without sacrificing performance, then the new engine is more efficient and desirable than the old engine. (True, some might argue that the new engine is better even if performance suffers; however, this is a matter of choice, rather than pure unbiased efficiency.) Similarly, if you waste a lot of energy compressing and stretching your crank arm, then your riding is inefficient and children on stingrays will pass you on hills.
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Efficiency is determined by comparing the necessary energy against the actual energy expended for a given task. This then begs the question, "what is the necessary energy?" Given that we're discussing bicycling, the necessary energy is defined as force multiplied by the distance moved relative to the force. For clarity, we can refer to this as the "useful work."
For example, if you spend an hour pushing on a 10-ton boulder, and if the boulder doesn't move, then you have done no useful work. You exerted a force, but the boulder didn't move, so all of your effort was wasted. What is your efficiency in this case? Simple answer: zero.
Now suppose we observe an asteroid flying through space. It is coasting along at high speed, but no force is being applied to it. How much work is being done? Answer: none. (Note for the purists: we're ignoring the gravitational force from nearby planets, black holes, and Vulcan battle cruisers.)
Obviously, when bicycling, it is best to be like the asteroid rather than the boulder. Maximum distance, minimum work. Smooth motion, not grunting struggle.
Now let's look at a human standing on the earth. The constant force applied to this human is… gravity. Yes, gravity is always pulling the human down, and straight down. (Again for the purists: we're ignoring the gravitational pull of large mountains, the moon, and Vulcan battle cruisers.) While you are standing still, your brain automatically coordinates the small muscle contractions necessary to maintain your balance. This means that your body is constantly expending energy, though very slightly. You work, though you do not move. What is your efficiency? Answer: zero. True, you are working; but you are performing no useful work.
Now suppose you take one step sideways on level ground. This requires a bit more energy than standing still. What is your efficiency? Not so obvious answer: zero. Why? Because you have not moved relative to the earth's gravitational force. You have not moved up or down. Instead, you have moved across the force.
To help illustrate, consider an ice skater gliding on smooth ice, with freshly sharpened skates. The skater can glide for a considerable distance, slowing only because of wind and friction between skates and ice. But if there was no wind, and no skate friction, then the skater would glide forever, never slowing, always at the same speed, while performing absolutely no useful work. This defines the necessary energy required to move across flat ground when there is no wind or friction: none.
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Now consider someone who runs a marathon across flat ground. Assume there is no wind, and that each step lands squarely on the ground without slipping. Without wind or friction against the ground, the only remaining force to contend with is gravity. And because the runner moves across this force, the useful work performed is… zero.
How can this be? How can you run so far and so hard, and collapse to the ground in exhaustion, and still perform no useful work? Simple answer: the entire marathon is a struggle against yourself. You flop along inefficiently, rather than gliding smoothly.
Straighten your arm. Now tighten all of the muscles in your arm, but don't allow your arm to bend. Your arm struggles against itself, and soon all of the muscles will become exhausted. But it goes nowhere and does nothing useful.
This brings focus to today's topic: human efficiency. It is a fact that you are always using energy and you are always wasting energy. Waste happens at a chemical level over which you have little control; but it also occurs during physical and voluntary processes that you can control. This control comes through coordination and flexibility. If you are coordinated, then your muscles will not fight each other, and they will cause only the desired motions. If you are flexible, then your limbs will bend and extend easily and without struggle.
On a bicycle, the desired motion is known: make circles with your feet. Round and round they go, where they stop, nobody knows. In truth this is a very complicated motion, involving many muscles large and small. If some are contracting when they should be relaxing, then you are fighting yourself and you will be slower than you could be.
Next time you're riding, try to identify the muscles used at various points in the pedal stroke, particularly at awkward points like the very bottom of the stroke. Try to relax the muscles that aren't being used. Try shifting into your highest gear while grinding along slowly. Get a feel for how things work. Don't push all the way to the bottom of the stroke. Pull up the back. Roll over the top. And always be as relaxed as possible. Don't fight with yourself, and truly ride smart, not hard.
"Ride Smart / Not Hard" is a regular column in the Eastern Idaho Bike Magazine. Can you think of a topic for
the next issue? Let Us Know!
Peter Jensen has resided in Eastern Idaho for 19 years. He is an avid cyclist, though a "non-racer" because
of his low melting temperature (above 75 degrees you'll find him frying up some beef liver and gummi bears on
the road). He is an Internet programmer and engineer, and like all true engineers is constantly thinking of
simple ways to make things easier.
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