From Wikipedia, the free encyclopedia
- For the journalism term, see Running (journalism).
Running is by definition the fastest means for an animal to move on foot. It is defined in sporting terms as a gait in which at some point all feet are off the ground at the same time. It is a form of both anaerobic exercise and aerobic exercise.
During running, the speed at which the runner moves can be calculated by multiplying the cadence (steps per second) by the stride length.
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Human running mechanics
Running is a complex, coordinated process which 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 now described in detail.
Support
During the support phase, the foot is in contact with the ground and supports the body against gravity. The body's center 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 body's center 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 ilio-tibial band of the supporting leg, the hip abductor, and the abdominals and lower back muscles. The knee flexion is opposed by the eccentric contraction of the quadriceps muscle. The supporting hip continues to extend and the body's center 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 hip, 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 center 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 driving toe loses contact with the ground, the recovery phase
begins. During recovery, the hip flexes, rapidly driving 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 into the support phase.
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Upper body motion
The motions of the upper body are essential in running, because they
compensate for the motions of the lower body, keeping the body in
rotational balance. A leg's recovery is matched by a downward drive of
the opposite arm, and a leg's support and drive motions are balanced by
raising of the opposite arm. The shoulders and torso are also involved.
Because the leg drive is slower than the kick of recovery, the arm
raising motion is slower also. The downward arm drive is more forceful
and rapid.
The more inefficient the motions of the lower body, the more
exaggerated do the upper body motions have to be to absorb the momentum.
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 center 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-center by a
projectile, it will rotate as well as recoil. If the projectile strikes
the body's center 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.
Running injuries
There are many injuries associated with running (due to it being a high impact activity). Common injuries are "runner's knee" (pain in the knee), shin splints, pulled muscles (especially the hamstring), "jogger's nipple" (soreness of the nipple due to friction), twisted ankles, Iliotibial Band Syndrome, and achilles tendonitis. 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-use. Repetitive stress on the same tissues without enough time for
recovery or due to improper form or muscle imbalances, leads to many of
the above. Generally these can be minimized by warming up beforehand, wearing proper running shoes, improving running form, performing strengthening exercises, and getting enough rest.
There is a very strong consensus among the running and scientific
community that all of those can be very effective in minimizing or
recovering from running injuries. Another injury prevention method that
is very commonly recommended in the running community but is actually
controversial is stretching. While stretching is often recommended as a
near requirement to avoid running injuries, the relevant medical
literature does not represent as much of a consensus that it is
effective. Some studies find that it is and some find that it really
isn't helpful at all. A 2002 systematic review
of 27 peer reviewed studies found that there was not sufficient
evidence to support the claim that stretching was effective in injury
prevention or soreness reduction.[1]
Most members of the running community find that the inconsistent study
methods and the failure to establish proper controls and find proper
stretching methods is the reason behind the conflicting studies, and
stretching is in fact helpful, or at least not harmful.
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Jogging
Jogging is a vaguely-defined term which generally refers to a
type of slow running, previously called "roadwork" when athletes in
training, such as boxers,
customarily ran several miles each day as part of their conditioning.
In the 1960s or 1970s the word "roadwork" was mostly supplanted by the
word "jogging" and this form of running became quite popular among many
people at that time in the United States.
Competitive running
Perhaps the most basic of athletic contests, running races are
simply contests to determine which of the competitors is able to run a
certain distance fastest. Today, competitive running events make up the
core of the sport of athletics.
Running competitions have probably existed for most of humanity's history, and were a key part of the ancient Greek Olympics, as well as the modern Olympic games.
Events are usually grouped into several classes, each requiring
substantially different athletic strengths and involving different
tactics, training methods, and types of competitors.
Running affects not only the body, but the mind
as well. Runners who finish a great run are sometimes said to have a
"runner's high" - which is more than a sensation of a strong feeling of
accomplishment and pride. Some sources point to the origin of a
runner's high being increased endorphin production as a result of exercise. However, many runners also do not experience this high.
Running in itself makes up its own competitive sport, but running is
also a very important aspect of other sports, i.e. soccer, basketball,
lacrosse,etc. Usually the running aspect of these sports is very
important to help move a ball to a goal. People of all running types
are needed; i.e. with speed, endurance, or agility.