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run
fast, run free The
most common response to the thought of stepping up the pace is to put
more effort into the stride. If the legs are already being over worked
due to a less than efficient technique, the centre of the brain (motor
cortex) that initiates the action has to send more impulses adding to
the traffic in the feedback loop. We have the sensation that we are
running quicker because of the increased effort, but are we using our
energy efficiently? The
next
time you want to increase your speed try the following method.
Initially, when you have decided to quicken the pace, observe what you
normally do to achieve this. After a minute, slow down to a comfortable
jogging pace and again think about raising the pace. This time do not think about running faster but instead just move your arms
quicker. If we think of only moving the arms faster, requiring less
energy, the legs will match the speed. Try the exercise and experience
the difference. The first time you speed up you will use your usual
habitual method, the second will feel different because it will be
unfamiliar. A
recent study at Harvard University
titled:
’Faster top running speeds are achieved with greater ground forces not
more rapid leg movements’, Weyand
et
al (2000) found that runners reach faster speeds not by repositioning
their legs more rapidly in the air but by other means. Head of research,
Peter Weyand
explains:
- When
you see someone running at top speed, his or her legs and arms are
swinging all over the place. There is just not enough active muscle
power available to account for all the motion you see taking place. So
where does the force come from? To determine what limits top running
speed, thirty-three runners of varied ability were monitored performing
at different speeds. Surprisingly the amount of time taken to reposition
the leg between steps (swing time) was approximately the same at top
speed for all runners. The slowest runner’s swing time almost matched
that of the 1996 Olympic 100 metre champion, Donovan Bailey
! So
if the swing time is not a factor, how do the faster runners achieve
higher speeds? The researchers discovered speed is determined by the
amount of force applied to the ground rather than how rapidly limbs are
moved through the air. The greater the force, called the support force
(SF), coming down through the body to the ground results in a greater
force pushing back up, called the ground reaction force (GRF). Remember
Newton’s third law of gravity! So those runners putting more into the
ground got more out of it. Peter Weyand
again:
- Much
of the work of running is done through passive mechanical processes, in
which tendons and muscles act though elastic rebound, much like springs
uncoiling, the uncoiling delivers the power to swing your legs. At
first this seems wrong because surely to run faster we need to move the
legs quicker. This study suggests that extra effort applied to moving
the legs faster may not therefore be the most efficient way to increase
speed. The upward thrust of the GRF is translated into forward motion by
the action of the hip, knee and ankle joints. If the act of trying to
move the legs faster leads to unnecessary muscle activity, joint
movement will be impeded therefore reducing the leg’s efficiency to
perform its task. When we run faster obviously the legs move quicker but
this should be a result of a greater force pushing the leg back up from
the earth (a recoil action). For example the harder you throw a tennis
ball at the ground the higher and faster it bounces back up. The faster
a leg comes up from the earth, the quicker it comes back down. The paper
summarises the results by stating: - We
conclude that human runners reach faster top speeds not by repositioning
their limbs more rapidly in the air, but by applying greater support
forces to the ground. The
study also found how the fastest runners achieve the characteristic
longer strides. It has been known for many years that longer strides
meant faster running. Coaches
encouraged
sprinters to practice taking longer strides and devised exercises to
strengthen appropriate muscles (many of which lead to injury). This now
appears to be wrong. Trying to lengthen the stride length decreases a
muscle’s ability to apply the support force required to get back up
for the next step. Runners are not faster because they take longer
strides. It is the other way around; runners take longer strides because
they are fast. They are fast because they apply greater support forces
to the ground allowing them to spend longer time in the air, hence the
longer stride. So
if the secret to achieving greater speed is to apply more force to the
ground, how do we go about doing it? I suspect that in the light of this
research there will be coaches looking to strengthen the muscles that
push the leg downward. However is this the right approach? Whilst muscle
strength is a factor, it could prove to be detrimental to performance if
all that strength is misapplied. In the act of trying to drive the leg
down, the athlete will increase the risk of injury due to increasing the
amount of stress placed on the joints. It may also reduce the recoil action if the joints are not
allowed to move freely. I
believe one facto Perhaps we can now understand why Michael Johnson’s upright style is a world-beater. To run faster we should do as little as possible. Our ‘efforts’ are more likely to impede free movement. Remember; less is more! Agree or disagree? Let me know click here Want to read more? click here
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