Running

Man Running - Edward Muybridge

File:Muybridge horse.jpg

Horse Running - Edward Muybridge

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 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.

Human Running Mechanics

Running is a complex, coordinated motion which involves the entire body. Every human being runs somewhat differently, but certain general features of the running motions 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 sprint running.

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. It should be noted that 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.

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 the people who compete at a high level in each respective event.

Jogging

Jogging is a poorly-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. Jogging is a "high-impact" exercise that places strain on the body, notably the joints of the knee. This is actually one of the basic reasons for doing the exercise, as the impact drives growth processes in the areas of the body stressed by that impact. Some dropped jogging in order to take up "low-impact" exercises such as stair climbing. Jogging can be combined with other kinds of exercising. Special trails that combine them are called trim trails.

Because jogging isn't a well-defined term, jogging cannot be classified as a competitive sport. There isn't any clear set of rules by which competitors could be disqualified for cheating by transitioning from jogging to running, other than the general observation that they are running with too good a form, and trying to win by moving too quickly.

A more precise definition of jogging may be that it is a form of running which, for the given individual performing it, and all other conditions held constant, is less efficient than walking. Above a certain pace, running is a more efficient form of locomotion than walking (less oxygen use per distance traveled). Below that pace, running is less efficient than walking and makes no sense as a means of covering a distance. A foot messenger delivering a message on foot over 60 miles of road could expend more energy jogging the distance at a thirteen-minute-per-mile pace than briskly walking it at the same pace.

US Marine running in a triathlon

Jogging is also characterized by poor form. Joggers, or runners who are jogging, sometimes move in ways that are not observed in competitive running. They demonstrate a hunched posture, carry their arms too high, and leap excessively high into the air and land heavily on the heel. Such form further wastes energy, and exacerbates the impact of the exercise. An elite long-distance runner can move three times as fast as a jogger, yet experience much less impact due to a smooth form that minimizes vertical motion, and which doesn't exhibit the heavy rear-foot landing during the footstrike.

Jogging is used by serious runners as a means of active recovery during interval training. The runner who may just have completed a fast 400 metre repetition at a sub-5-minute mile pace, may drop to an 8-minute mile pace for a recovery lap. The jog might be carried out in much poorer, looser form whose purpose is to "shake out" the body and maintain circulation to eliminate, from the muscles, metabolic waste products produced during the bout of hard work.

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 often said to have a "runner's high" - 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.

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, and Iliotibial Band Syndrome. 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.

Types of running events

• Track running
• Road running
• Cross-country running
• Trail running
• Fell running

Classification of running by distance

• Sprints
• Middle distance
• Long distance
• Ultrarunning
• Multiday running

See also

• Training effect
• Exercise hypertension
• Stretching
• The Side stitch (cramp/pain under the ribs)
• The foot
• Runner's World