Steve McCaw

Biomechanics has all kinds of practical applications — from the construction of running shoes to ankle braces to low-back pain to weightlifting. Knowing how the body moves because of the forces applied to the body is key to getting the most out of your athletic performance, and your daily life.How Running Shoes WorkHumans have been running for millions of years.

Humans have been running for millions of years. Large forces are produced at the foot–ground interface when running. The force from the ground stops the downward motion and slows the forward motion of the runner during the first half of ground contact, and then propels the runner upward and forward into the next running step during the second half of ground contact.

Low-back pain affects many people. It’s often said that a person with low-back pain suffers from a “slipped disk,” but the better term is a bulging disk. Regardless of what it’s called, low-back pain is very debilitating, causing both pain and muscle weakness. The spine is the backbone of the body. It consists of 24 individual bones called vertebrae.

An ankle sprain is one of the most common injuries in sport and recreation. Typically, the ligaments on the outside of the ankle are sprained when someone “rolls” his or her ankle. Ligaments are tough connective tissue running from bone to bone to help support a joint. Ligaments consist primarily of the fibers elastin and collagen, aligned to provide support and flexibility to the joint.

Talk in a weight room among experienced lifters may revolve around “doing negatives.” This doesn’t mean they’re going to stop exercising and go for a snack. “Doing negatives” refers to a particular way to perform an exercise. It’s weight room jargon, but it’s also talking biomechanics. Positive work is performed when a force is applied to a body, and the body moves in the direction of the applied force.

Solving for the resultant force created when multiple forces act on a body involves several steps. The steps include using the tools of math and trigonometry to work with force vectors. Using a systematic approach makes it easier to arrive at the correct answer. With vector quantities like force, the direction of the vector is as important as the magnitude.

The following ten principles of biomechanics provide a solid basis for looking at performance, whether it's coaching, teaching, rehabilitation, teaching a kid in the driveway, or watching a sporting event on TV. You can think of these principles as a list for quick reference. There may only be ten principles covered here, but seeing how they apply will keep you busy for the rest of your movement-analyzing days.

Astronauts float around the interior of the space shuttle because they’re in a gravity-free environment. This creates a unique problem for the astronauts trying to get work done up there: how to turn around. Because they’re floating, when astronauts needs to turn around, they can’t do it as easily as you can on earth.

Each muscle in the body includes many motor units. A motor unit consists of a group of individual muscle fibers that are activated by a single motor neuron. When stimulated by an action potential transmitted along the motor neuron, all the fibers in a motor unit develop muscle tension (a pulling force) at the same time.