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You can pedal a bike well
enough to get by, or you can pedal a bike efficiently and get the
most out of the incredible mechanical advantage that's available.
To make the most of your gearing and aerodynamics you must use all
the leverage available at your bike/body connection - your bike's
crank arms. For anyone who's tried to loosen a tight nut or bolt with
a wrench, the advantage of maximum leverage is simple to understand.
This same leverage principle applies to optimal energy transfer at
your crank arms. To loosen that bolt, or apply maximum pressure
to the cranks, the force applied should be perpendicular (at
a 90 degree angle) to the lever (crank arm), and the further from
the pivot point that you push on the crank arm the more force you
generate. On a bike, the pivot point or fulcrum is the axle of your
bottom bracket, and the length of your lever (crank) determines maximum
leverage. This potential won't change unless you install longer cranks,
but your cranks are likely already at maximum length for effective
pedaling in proportion to your leg length. So this leaves the angle
from which you apply pressure to the crank arm as the only variable
you can modify (besides increasing force/wattage output from the engine—you).
This is challenge for some cyclists, but the rewards are well worth
the effort!
The simple exercise of just pushing down on the cranks to make
the bike move becomes more complicated. As an example of wasted
energy: consider what happens when you simply push straight downward
with the crank arms at the 12:00 o'clock and 6:00 o'clock positions—absolutely
nothing. We all learned this early on when we struggled through
our first few pedal strokes on that little tricycle or coaster-brake
bike. Have you ever watched a child try to get his or her bike moving
when the pedals are in this position? After a while it becomes clear
that in order to get the child started you have to either give a
push, or pick the bike up and rotate the cranks 90 degrees to 3
and 9 o'clock positions. Optimal pedaling technique is no more natural
than a perfect swim stroke, it must be learned.
To get the most out of your cycling, you need to analyze your pedal
stroke and identify the weak spots. There's more involved with efficient
pedaling than just pushing downward with a lot of force. I've identified
three points of your pedal stroke where you can gain energy output:
Pushing forward over the top, pulling back at the bottom, and lifting
the weight of your leg as it moves back up to the top during the
'backstroke.' Cycling isn't a natural motion that we've repeated
every day since childhood, like walking is for running. Try to develop
this pedaling power flow as I've described; it will be worth the
effort. Without any extra work to increase aerobic capacity you
can gain speed by perfecting your pedaling technique.
Figure 1. The difference in the leverage potential
of the right crank arm with pedaling force applied from two different
directions (clockwise crank rotation).
These examples are leading up to a thorough analysis of how to
push in powerful circles with your legs. Figure 1 examines the critical
range of motion over the top of the pedal stroke. This particular
point of the pedal stroke can be either a powerless 'dead spot,'
or an extra bonus bit of energy with a little technique work. The
challenge is to push your foot forward over the very top of the
stroke, and then continue the forward pressure as you begin your
down stroke. Figure 1 illustrates the optimal direction of force
(A) and the more typical, yet less effective direction of force
(B). Figure 1 also shows the amount of leverage available with the
average Pedal stroke (B), and the more efficient technique A). The
diagonal line (A) which runs parallel to the crank arm represents
the effective length of the lever when the pressure is applied perpendicular
to the crank. The two lower lines (A) and (B) compare the difference
of the effective lever length when the power is applied from direction
(A) or (B). Notice that pushing from angle (B) directs about one
third of the energy to pushing the crank arm toward the bottom bracket.
This is similar to pushing the crank straight downward when it's
at the 12 o'clock position. Direct downward force at the fulcrum
(bottom bracket axle) contributes nothing to the turning or torque
movement necessary to pull on the chain at the chain-rings, which
in turn pulls on the sprockets at the back wheel. Therefore, with
an equal amount of muscular power available, pushing only downward
(B) can generate only two-thirds the force that is possible by pushing
both forward and down simultaneously (A). In the weight room, the
leg extension machine, (not the leg press) which focuses on pushing
your lower leg forward from the knee, works well to develop this
particular muscle action by developing your vastus-medialus (inner
quad just above the knee).
But how can you develop your pedal stroke to improve this part
of your stroke without going to the weight room? The most obvious
is simply to get a feel for forward pressure at this part of the
pedal stroke while sitting on your bike in a static position. To
get a good feel for this while moving, try the pedaling with one
leg drill. To do this, just click one foot out of the pedal and
push forward, down, pull back and lift up on the "back stroke"
with only one leg. Apply some resistance like light braking or do
the drill on a slight uphill in a low gear, and try to feel an even
pressure all the way around in a smooth circular motion. If your
pedaling motion with one leg is jerky, or worse still, if there
are points where your freewheel is not engaged at all, keep working
on it. These "dead spots" where you apply no power are
clearly the weak spots in your pedal stroke; you can become more
efficient and therefore faster by getting a feel for where you could
apply more power.
Here is another obvious reason to refine your pedaling technique.
As you pedal, your leg must move from the bottom-most position,
back up to the upper-most position at the top of the pedal stroke
with each rotation of the cranks. Let's call this upward motion
the "backstroke" or "recovery." Now let's assume
each of your legs weighs 15 pounds. If you generate absolutely no
lifting energy with that recovery leg, then you're using up 15 pounds
of your downward force from your quadriceps of the opposite leg
to push that recovery leg back up. What a waste of energy! The hip
flexor is the muscle that can lift your leg up during this pedaling
recovery or backstroke. It is a relatively weak muscle, but well
developed in runners, and quite capable of lifting the full weight
of your leg repeatedly, thus nullifying the energy loss of pushing
your leg back up at each rotation.
So I've talked about the possibility of increasing efficiency and
power by pushing forward over the top of the pedal, stroke, and
lifting the weight of your leg on the recovery or backstroke, but
there's one more crucial point of the circle where we can generate
energy output. This is the range of motion between points (4) and
(6) on Figure 2. At this point of the pedaling action we can use
our well-developed runners' hamstring muscles. I know many of you
with cleated bike shoes already utilize this part of the pedal stroke
to your advantage. This motion should be the second most powerful
part of the stroke when you get it right, after the dominant downward
push from your quadriceps muscle group. The sensation of pulling
backwards from an extended leg should feel like scraping something
off the bottom of your shoe.
Figure 2. Optimal foot angle relative to lower
leg at various points in the pedal stroke as viewed from the right
side (clockwise rotation).
Figure 2 illustrates an idealized pedal stroke with the best possible
angle of your feet relative to your lower leg to generate the most
power around the circle. You might say, "I just watched a bike
race on TV and the pro racers didn't pedal that way." If you
watch closely though, you will see that the slower their cadence,
the more they drop their heel (flatten the angle of their foot relative
to the ground) over the top of the pedal stroke. Typically when
you're spinning (pedaling fast with little resistance) you don't
need to generate much power and your foot favors the least possible
movement at the ankle, thus maintaining a perpendicular angle to
your lower leg. But as you pedal more slowly, perhaps needing more
power for a climb or to push through a headwind, modifying the angle
of your foot at various points of the pedal stroke can increase
your power. Here's why it helps at the top of the stroke: The power
that your dominant quadriceps muscle can generate increases as your
leg straightens. This can be demonstrated by experimenting with
the amount knee flexion versus max weight lifted on a leg press
machine. So, you already know a longer crank arm can give more leverage,
but on the other hand, the less you bend your knee the more powerful
your push. Obviously, this is a bit of a conflict on a bike, due
to the large circle created by each crank rotation. When you understand
these two limitations, it follows that if you can pedal with a straighter
leg you should be able to apply more power at the crank arm. The
only way to do this is to bend your knee less, which can only be
accomplished by your knee rising less at the top of the pedal stroke.
Dropping your heel, keeping your foot flatter relative to the ground
over the top of the pedal stroke is the way to do this. You can
see this change in pedal stroke in comparing spinning with low pressure,
then on the saddle while climbing hard at low cadence. The difference
between the heel high or heel low position over the top is small
but it can help you develop more power when you need it. This even
applies during the current trend toward spinning; even Lance changes
his stroke when more wattage is needed for short periods.
Take a look at Figure 2 from point (2) to point (5). Over this
range of the circle the angle of foot to lower leg changes, from
flexed (flatter) to extended (pointed slightly downward). This is
the only range of the pedal stroke where the calf muscle gets to
contribute some force by contracting. But, take note though, that
this extra energy contribution can't happen if your foot is already
pointing slightly downward at points (2) and (3). So, from these
last two paragraphs, we've learned of two reasons that the angle
of our foot to lower leg is critical to pedaling efficiency. This
flexion at the ankle requires moderate flexibility of the joint
but I've never seen a runner who doesn't have the ability to do
this on the bike. I should also say that in some old school cycling
manuals this technique is called "ankling," and requires
much time a patience to develop. Of course you could ride 600-mile
weeks like pro bike racers and the proper pedal stroke will probably
come naturally by necessity!
Each range of the pedal stroke contributes a different amount of
force with inherent muscle strength limitations. I estimate that
the forward push over the top contributes about 10%, the down stroke
about 65% (including the small calf push near the bottom), and the
pull back about 25%. Even though the muscles are working to lift
the weight of the leg, the lifting action on the recovery probably
contributes little or nothing for most cyclists on a flat road.
But when standing on the pedals (while out of the saddle), sprinting/accelerating,
or at low rpm on a climb, the hip flexors and hamstrings should
supply a significant amount of temporary power. A significant amount
of force can be generated by pulling up for short periods, but only
when you really need it.
So far I've mentioned the term "spinning" with only a
brief description when in fact, to develop a smooth spin should
be a prerequisite. I've left spinning for last because it's recommended
that you do the bulk of your spin work during the off-season base
mileage building period. Most bike racers who started young had
to race with a gear restriction early on. The reason is to develop
a proper pedaling action, and to save young tendons and joints from
the stress of over gearing. Spinning is useful because the unusually
fast rate of muscle contraction teaches your neurological system
to send each muscle stimulating electrical signal at exactly the
correct moment. In order for each of these intricate pushing, pulling,
and lifting operations to take place a very specific muscle(s) must
contract and then relax. It's not uncommon for the "uneducated
leg" to have opposing muscles contracting at the same time,
and this is very inefficient. Spinning is defined as a cadence of
greater than 95 rpm, and typically less than 120 rpm on the road.
Most bike racers can spin smoothly with no bounce on the saddle
to significantly over 120 rpm. The best way to develop your spin
is to self-impose a gear restriction for a certain stretch of road.
Be patient, because spinning takes time to master. Easy, or 'active
recovery' are ideal days to practice spinning in-season.
To get the most out of your cycling, you need to analyze your pedal
stroke and identify the weak spots. There's more involved with efficient
pedaling than just pushing downward with a lot of force. I've identified
three points of your pedal stroke where you can gain energy output:
Pushing forward over the top, pulling back at the bottom, and lifting
the weight of your leg as it moves back up to the top during the
'backstroke.' Cycling isn't a natural motion that we've repeated
every day since childhood. Try to develop this pedaling power flow
as I've described; it will be worth the effort. Without any extra
work to increase aerobic capacity you can gain speed by perfecting
your pedaling technique. |
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