No part of the body has a weightier role to play than the feet. These multipurpose appendages allow us to walk, saunter, jog, run, jump, skip or hop for miles at a time.

Feet aren't just for locomotion; they can serve as a second pair of hands. Who hasn't picked up a towel from the floor or turned a VCR knob by grasping it between the toes? Some exceptionally dextrous sorts can pick up coins or other small objects this way. This substitution can be literally true. A big toe can replace a thumb that has been lost. And toes, to some extent, can replace lost fingers.

It's less known that feet are organs of thermoregulation. When you're cold, your body reduces blood flow to feet and the other extremities to keep the vital organs warm. That's one reason why toes (and fingers) are vulnerable to frostbite.

When you're getting too hot, the opposite happens. Blood flow increases to the feet, where the heat is radiated away and removed by evaporation of sweat. At least, that happens if you're barefooted, or at least wearing open-topped footgear such as sandals. Feet suffocated inside the sauna of closed shoes don't give that relief, so liberating them as often as feasible is healthy.

Elephants "hear" through their feet; that is, they sense low-frequency ground vibrations emanating from as much as 20 miles away. A study of this ability was published in 2001 in the Journal of the Acoustical Society of America. The study authors, from Stanford University, hypothesized that the vibrations traveled through the feet into the skeleton and then into the ear.

Humans have this ability as well. If strong vibrations pass through a structure you're standing on, you may be able to "hear" them, similar to how you perceive the vibrations of a tuning fork touched to your head. However, the gecko's feet arguably have the neatest trick of all: They are covered with billions of microscopic "nanohairs" that enable the lizard to walk on vertical walls or even upside down on ceilings.

Of course, all these marvelous abilities are secondary to the feet's star role of getting us (human, elephant or gecko), where we want to go. To that end, human feet have three main points of contact with the ground: the toes, the ball of the foot, and the heel. The pattern of contact changes with each method of locomotion.

The heels and ball provide solid support. The toes, especially the big toe, fine-tune this support with balance. That balance is especially noticeable with bare feet. The degree of control approaches that of the hand; not surprising considering their anatomical similarities.

Most of the foot's 26 bones can be paired up with corresponding bones in the hand. The 14 phalanges (fingerbones) and five metacarpal bones just below the phalanges pair with the 14 toe bones and the five metatarsals just below them.

This fine control, along with that of the leg muscles and flexing at the knee, gives humans the ability to cross over terrain from the nearly smooth surface of a tiled floor to more challenging acts of locomotion such as walking across sand, climbing stairs or climbing mountains. The most sophisticated ambulatory robot in existence is left behind in the dust by the adaptability of human foot power.

With all the stress we place on our feet daily, they are vulnerable to a variety of ailments from overuse or improper use. Basketball players, with their constant jumping, are prone to stress fractures. These are small breaks in bones that can tear wider if untreated.

When people get foot fractures without having engaged in such foot-stressing activity, it could be a sign of osteoporosis. A study by Ohio State University researchers in March 2000, found that 20 out of 21 patients with foot fractures either had osteoporosis or early signs of the disease.

However, diabetes is an even bigger threat to feet. Diabetes often results in poor circulation to the extremities, with the feet being most vulnerable. Deprived of blood, diabetic feet are prone to develop ulcers, possibly leading to amputation of toes, the entire foot, or even the lower leg.

The Lancet, a British medical journal, stated on Nov. 14, 2005, as many as 15 percent of diabetics worldwide develop foot ulcers and more than 1 million diabetic-related amputations take place each year.

This June, a study in the journal Diabetes Care stated that diabetics who get infections have 154 times the risk of amputation of diabetics without infections. Moreover, nearly 90 percent of amputations were performed in response to an infection. Poor circulation, however, is an important contributing factor in determining the extent of the amputation.

Short of this drastic threat, feet can be just plain sore from excessive or unaccustomed use, blistered, bunioned or mildly traumatized, as with the all-too-familiar toe stub in the dark.

For information on foot health, walk on over to the American Podiatric Medical Association's Web site at www.apma.org/s_apma/sec.asp?CID=14&DID=2825.

Contact staff writer Bradley J. Fikes at (760) 739-6641 or bfikes@nctimes.com.