There are a few basic laws and principles of physics that can help you better understand why you can race walk, and why you need to develop good walking techique. Physics can be VERY complicated, but I think I can explain the "why" fairly easily--and without any mathematics.
The animation of champion race walker Jefferson Perez at right is the same animation shown on the Home page of this Web site--with two differences. First, I changed the background for emphasis--so there is really only one significant difference. Through the magic of animation, this clip shows him walking about 6 inches above the ground--and going absolutely nowhere. Using the same outstanding technique and style as he does on the Home page, here he simply looks like an idiot who is flailing his arms and legs. So, what is the difference?
The difference has to do with basic laws of physics that were first defined by Sir Isaac Newton in his Law of Gravity and his three Laws of Motion.
- Law of Gravity: Gravitation is a natural phenomenon by which objects with mass attract one another. Its strength is based on the relative size of objects and the distance between them. Larger objects exert a greater force of attraction than smaller object, and the force of attraction is greater the closer they are together. For example, the earth attracts the moon thereby keeping it in orbit around the earth, and the moon also attracts the earth as evidenced by ocean tides. For race walkers, gravity is critical because it pulls us toward the earth with enough force to make us fall when we lean at an angle other than vertical, and because it creates the friction which allows our feet to get traction with the ground. (In Figure 1, Perez, with gravity suspended, can not get traction with the ground.)
- First Law of Motion (on momentum/inertia): Momentum is the natural phenomenum that keeps a stationary object stationary, and a moving object moving in the same direction at the same speed unless acted upon by some external force. For race walkers, momentum defines how we change our walking speed or direction (including starting and stopping), and how we change the relative speed and direction of our shoulders, arms, torso, hips, and legs as well work through the process of walking. (In Figure 1, Perez, being off the ground and with gravity suspended, has not been able to generate any force that would cause him to begin to move forward.)
- Second Law of Motion (on acceleration) An increase in speed is produced by a particular force acting on an object, where more force creates a greater increase and a larger object sees less increase from the same amount of force. In other words, to go faster, you will have to work harder or weigh less. For race walkers, this translates into training harder, keeping your weight reasonable, wearing lighter shoes, and use a good technique--one that does not waste energy.
- Third Law of Motion (on reaction) For every action, there is an equal but opposite reaction. This law is a bit harder to understand because it is not quite so visible. For example, if you try to push a box across the floor, a box that is your same weight and has the same traction, your feet will be pushing the floor in the opposite direction, AND the floor will be pushing back against your feet with an equal force (I believe due to friction). The net result will be that nothing moves. If, however, you reduce the box's weight slightly (or lubricate the floor to reduce the box's traction), the box will begin move. For race walkers, this means that, if you push back on the ground (with gravity and proper shoe and road conditions giving you traction), your body will move forward.
- Torque is a rotational force applied to an object. Torque is the force you apply to a screwdriver to insert or remove a screw. Torque is the force applied to a bicycle tire by way of the legs, pedals, and chain that will, with proper tire traction, translate into the bicycle moving forward. For race walkers, torque is the force applied on the thigh by the hamstring muscles that, via lower leg and foot, causes the foot to push backward--which, with good foot traction, will cause the hips to move forward. It is also torque that makes the shoulders, arms, hips, and legs swing and/or rotate while using good race walking technique.
- Pendulums are hinged arms that have a mass at the free end (and, in the real world, along the arm itself). A pendulum has its mass below the hinge, swings at the lower end when activated by an external force, and is stable when hanging vertically. Pendulums with shorter arms complete a full swing faster. The arms of a person are compound pendulums that swing from the shoulders and elbows; the legs of a person are compound pendulums that swing from the hips, knees, and ankles (unless a leg is supporting the body--whereupon it becomes an inverted pendulum). +++ An inverted pendulum has its mass above the hinge, is naturally unstable, and only stays inverted if an external force holds it in place. The body of a standing person is an inverted pendulum which falls down if not held in place by torque generated about the ankles or by moving the position of the hinge (e.g., shifting the support from one leg to the other. +++ For race walkers, the pendulum action of the swing leg works with the inverted pendulum of the stance leg and torso to allow the person to walk; and the pendulum actions of the swinging arms allow the person to walk faster.
- "Center of Mass" (COM) The Center of Mass is that point in an object where the amounts of mass on opposite sides in any direction are equal. For a ball, it is in the center of the ball. For a wheel, it is in the center of the axle (or weights will need to be added to "balance" the wheel). For a complex shape like a race walker, it is that point in the body where the person, suspended by a rope from that point, would be in balance no matter which direction his body was pointing. The COM of a person is usually inside the body just above the navel, but could actually be outside the body if the person is sitting on the ground with legs straight and touching his toes. The COM is usually the same as the Center of Gravity. For race walkers, the COM is important because the greatest efficiency (conservation of energy) occurs when the COM is not changing speed or direction (see "momentum')--i.e., the walker is gliding along without significant movement up, down, or sideways. The photo animation of Jefferson Perez on the Technique page is an outstanding example of such "gliding." The moving masses of the arms and legs counterbalance each other, and his heads bobs very little, so that the total mass of his body stays very near the same spot.
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