HOW WE WALK: Walking is different from a running gait because only one foot at a time lifts off the ground. During forward motion, the leg that leaves the ground swings forward from the hip, like a pendulum. Then the leg strikes the ground with the heel and rolls through the toe in a motion similar to an inverted pendulum. The motion of the two legs is coordinated so that one foot or the other is always in contact with the ground -- a so-called 'double pendulum' strategy. The process of walking recovers about 60% of the energy expended thanks to the pendulum dynamics and the ground reaction force. (The legs act as long levers that transfer ground reaction force to the spine.)
ON ONE'S TOES: Vigilance is an area of human factors and ergonomics research that looks at people's ability to stay focused on a task over long periods, such as someone monitoring the controls at a nuclear power plant. The challenge is how to keep alert when nothing of concern is happing, so that when a problem does occur, it will be recognized and dealt with quickly.
PROBLEMS FROM PARKINSON'S: Many people suffering from Parkinson's disease experience progressively greater difficulty walking, a condition known as akinesia that is thought to result from depletion of the neurotransmitter dopamine in the brain's movement control centers. The most common gait problems are freezing and small little stuttering steps. Drug treatment can help alleviate this condition, but also has undesirable side effects.
The Human Factors and Ergonomics Society contributed to the information contained in the TV portion of this report.