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Human running mechanics
Running is a complex and coordinated process that
involves the entire body. Every human being runs
differently, but certain general features of running
motion are common.
Lower body motion
Running is executed as a sequence of strides, which
alternate between the two legs. Each leg's stride can be
roughly divided into three phases: support, drive, and
recovery. Support and drive occur when the foot is in
contact with the ground. Recovery occurs when the foot
is off the ground. Since only one foot is on the ground
at a time in running, one leg is always in recovery,
while the other goes through support and drive. Then,
briefly, as the runner leaps through the air, both legs
are in recovery. These phases are described in below.
Support
During the support phase, the foot is in contact with
the ground and supports the body against gravity. The
body's centre of mass is typically somewhere in the
lower abdominal area between the hips. The supporting
foot touches ground slightly ahead of the point that
lies directly below the body's centre of mass. The knee
joint is at its greatest extension just prior to the
support phase; when contact is made with the ground, the
knee joint begins to flex. To what extent it flexes
varies with the running style. There exist stiff-legged
running styles which reduce knee flexion, and looser, or
more dynamic running styles which increase it. As the
supporting leg bends at the knee, the pelvis dips down
on the opposite side. These motions absorb shock and are
opposed by the coordinated action of several muscles.
The pelvic dip is opposed by the Tensor fasciae
lataeilio-tibial band of the supporting leg, the hip
abductor, and the abdominals and lower back muscles. The
knee flexion is opposed by the Muscle
contractionEccentric contraction|eccentric contraction
of the quadriceps muscle. The supporting hip continues
to extend and the body's centre of mass passes over the
supporting leg. The knee then begins to extend, and the
opposite hip rises from its brief dip. The support phase
begins to transition into drive.
Drive
The support phase quickly transitions into the drive
phase. The drive leg extends at the knee joint, and at
the hips, such that the toe maintains contact with the
ground as that leg trails behind the body. The foot
pushes backward and also down, creating a diagonal force
vector, which, in an efficient running style, is aimed
squarely at the runner's centre of mass. Since the
diagonal vector has a vertical component, the drive
phase continues to provide some support against gravity
and can be regarded as an extension of the support
phase. During the drive, the foot may extend also, by a
flexing of the soleus and gastrocnemius muscle in the
calf. In some running styles, notably long-distance
"shuffles" which keep the feet close to the ground, the
ankle remains more or less rigid during drive. Because
the knee joint straightens, though not completely, much
of the power of the drive comes from the quadriceps
muscle group, and in some running styles, additional
power comes from the calves as they extend the foot for
a longer drive. This motion is most exhibited in
sprinting.
Recovery
When the driving toe loses contact with the ground,
the recovery phase begins. During recovery, the hip
flexes, which rapidly drives the knee forward. Much of
the motion of the lower leg is driven by the forces
transferred from the upper leg rather than by the action
of the muscles. As the knee kicks forward, it exerts
torque against the lower leg through the knee joint,
causing the leg to snap upward. The degree of leg lift
can be consciously adjusted by the runner, with
additional muscle power. During the last stage of
recovery, the hip achieves maximal flexion, and, as the
lower leg rapidly unfolds, which it does in a passive
way, the knee joint also reaches its greatest, though
not full, extension. During this extension of the leg
and flexion of the hip, the hamstring and gluteal
muscles are required to rapidly stretch. Muscles which
are stretched respond by contracting by a reflex action.
Recovery ends when the foot comes into contact with the
ground, transitioning again into the support phase.
Upper body motion
The motions of the upper body are essential to
maintaining balance and a forward motion for optimal
running. They compensate for the motions of the lower
body, keeping the body in rotational balance. A leg's
recovery is matched by a forward drive of the opposite
arm, and a leg's support and drive motions are balanced
by backward movement of the opposite arm. The shoulders
and torso are also involved. Because the leg drive is
slower than the kick of recovery, the arm thrusting
backward is slower also. The forward arm drive is more
forceful and rapid.
The more force exerted by the lower body, the more
exaggerated do the upper body motions have to be to
absorb the momentum. While it is possible to run without
movements of the arms, the spine and shoulders will
generally still be recruited. Using the arms to absorb
the forces aids in maintaining balance at higher speed.
Otherwise, optimal force would be hard to attain for
fear of falling over.
Most of the energy expended in running goes to the
compensating motions, and so considerable gains in
running speed as well as economy can be made by
eliminating wasteful or incorrect motions.
For instance, if the force vector in the drive phase
is aimed too far away from the centre of mass of the
body, it will transfer an angular momentum to the body
which has to be absorbed. If a free body in space is
struck off-centre by a projectile, it will rotate as
well as recoil. If the projectile strikes the body's
centre of mass exactly, the object will recoil only,
without rotating.
The faster the running, the more energy has to be
dissipated through compensating motions throughout the
entire body. This is why elite sprinters have powerful
upper body physiques. As the competitive distance
increases, there is a rapid drop in the upper body and
overall muscle mass typically exhibited by the people
who compete at a high level in each respective event.
Elements of good
running technique
Upright posture and a
slight forward lean
Leaning forward places a runner's center of mass on
the front part of the foot, which avoids landing on the
heel and facilitates the use of the spring mechanism of
the foot. It also makes it easier for the runner to
avoid landing the foot in front of the center of mass
and the resultant braking effect.
Stride rate
Exercise physiologists have found that the stride
rates are extremely consistent across professional
runners, between 185 and 200 steps per minute. The main
difference between long- and short-distance runners is
the length of stride rather than the rate of stride
During running, the speed at which the runner moves
may be calculated by multiplying the cadence (steps per
second) by the stride length. Running is often measured
in terms of pace in minutes per mile or kilometer.
Running versus
walking
In walking, one foot is always in contact with the
ground, the legs are kept mostly straight and the center
of gravity rides along fairly smoothly on top of the
legs; in comparison, humans actually jump from one leg
to the other while running. Each jump raises the center
of gravity during take-off, and lowers it on landing as
the knee bends to absorb the shock. At mid arc, both
feet are momentarily off of the ground. This continual
rise and fall of bodyweight expends a tremendous amount
of energy opposing gravity and absorbing shock during
take-off and landing.[4]
. The act of running involves using more energy to
accomplish travel over the same distance and running is
a less efficient means of locomotion in terms of
calories expended, though it is faster.
Running injuries
Due to its high-impact nature, there are many
injuries associated with running. Common injuries
include "runner's knee" (pain in the knee), shin
splints, pulled muscles (especially the hamstring),
"jogger's nipple" (irritation of the nipple due to
friction), twisted ankles, iliotibial band syndrome,
plantar fasciitis, and Achilles tendinitis. Stress
fractures are also fairly common in runners training at
a high volume or intensity. The most common
running-related injuries are due to over-exertion or bad
running form.Repetitive stress on the same tissues
without enough time for recovery or running with
improper form can lead to many of the above. Generally
these injuries can be minimized by warming up
beforehand, wearing proper running shoes, improving
running form, performing strength training exercises,
eating a well balanced diet, getting enough rest and
"icing" (applying ice to sore muscles, or taking an ice
bath). Ice immersion is a very effective modality in the
treatment of subacute injuries or inflammation, muscular
strains, and overall muscular soreness. For runners in
particular, ice baths offer two distinct improvements
over traditional techniques. First, immersion allows
controlled, even constriction around all muscles,
effectively closing microscopic damage that cannot be
felt and numbing the pain that can. One may step into
the tub to relieve sore calves, but quads, hams, and
connective tissues from hips to toes will gain the same
benefits, making hydrotherapy an attractive preventive
regimen. Saint Andrew’s cross-country coach John
O’Connell, a 2:48 masters marathoner, will hit the ice
baths before the ibuprofen. "Pain relievers can disguise
injury," he warns. "Ice baths treat both injury and
soreness." The second advantage involves a physiological
reaction provoked by the large amount of muscle
submerged. Assuming one has overcome the mind’s initial
flight response in those first torturous minutes, the
body fights back by invoking a "blood rush." This rapid
transmission circulation flushes the damage-inflicting
waste from the system, while the cold water on the
outside preserves contraction. Like an oil change or a
fluid dump, the blood rush revitalizes the very areas
that demand fresh nutrients. Make sure not to stay in
any longer than 15 minutes; 10 minutes is usually
sufficient. There is a strong consensus among the
running and scientific community that all of those can
be effective in both minimizing and recovering from
running injuries
Another injury prevention method common in the
running community is stretching. Stretching is often
recommended as a requirement to avoid running injuries,
and it is almost uniformly performed by competitive
runners of any level. Recent medical literature,
however, finds mixed effects of stretching prior to
running. One study found insufficient evidence to
support the claim that stretching prior to running was
effective in injury prevention or soreness reduction,
Another, however, has demonstrated that stretching prior
to running increases injuries, while stretching
afterwards actually decreases them. The American College
of Sports Medicine recommends that all stretching be
done after exercise, this is when the muscles are most
warmed up and capable of increasing flexibility. Recent
studies have also shown that stretching will reduce the
amount of strength the muscle can produce during that
training session.
Inconsistent experimental methodology and the failure
to use proper stretching methods are reasons given to
explain the conflicting results. Because of this,
members of the running community argue that stretching
remains helpful.
Jogging
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