By David Goldstein

Everyone has wished, at one point or another, that they had the strength to lift a car off of the ground, or break through a brick wall with the pound of a fist. You know, typical superhero stuff. But everyone who has tried it knows that most of the time reality, and the limits of the human body, spoil the fun.

Thankfully, scientists have been developing a way around those limits, in the form of wearable exoskeleton robots capable of increasing our strength, stamina and speed.

These aren't the massive, clunky brutes of old sci-fi movies, but nimble extensions of the human body with the gift of intelligence. They work by sensing and anticipating the movements of the person wearing the suit, using their own power to minimize the efforts of the user.

While most of us probably won't be living out our superhero (or evil villain) fantasies, these robots have some very practical applications, both military and civilian.

Here are the top five exoskeleton robots that stretch the limitations of our bodies and our imaginations.

1. Raytheon Sarcos Exoskeleton

Designed primarily with military purposes in mind, the XOS Exoskeleton, developed by Sarcos (purchased by Raytheon Integrated Defense Systems in Massachusetts), is the robot perhaps most like the popular comic book character Iron Man. While it doesn't shoot missiles or have boots with rocket thrusters in them, it does allow the wearer to lift or carry up to two hundred pounds repeatedly without tiring. It's unique because it's one of the few full-body exoskeleton robots available. Most robot exoskeletons are broken up into either legs or arms.

The idea is that a soldier wearing one of these robots could carry heavy gear over long distances without getting tired; rescue wounded soldiers from the battlefield with ease; or singlehandedly wield a weapon that usually requires two people to operate.

The major challenge has been engineering a power source that will power the robot from four to 24 hours. Right now the Exoskeleton can't operate that long without being plugged into some external power source, but the engineers are working on making it completely self sustaining.

2. Human Assistive Limb Exoskeleton (HAL)

Want to look your best for a big night on the town? CYBERDYNE Inc. in Japan understands. For those of you obsessed with accessories, this robot is a little more wearable than the others. The Human Assistive Limb Exoskeleton, or HAL, is a "cyborg type" robot designed to help people with mobility problems, in rehabilitation, and for heavy lifting. Although, if you visit the company's Web site, at first glance it looks as if the robot is designed to help you become a kung-fu master.

Associated Press, U.S. Army

HAL isn't all aesthetics though. It also has brains and beauty. In one sense HAL is a mind reader, as it uses electrical signals sent to muscles from the brain to anticipate the wearer's movement. It then calculates how much power the user intends to produce and directs the right amount to the right joints on the exoskeleton. HAL's ability to anticipate movement allows it to move fractions of a second before you do, providing seamless interaction between human and robot. And with its clean, sleek design you'll be the bell of the robot ball.

3. Human Universal Load Carrier (HULC)

Like the Raytheon Sarcos Exoskeleton, the Human Universal Load Carrier (HULC) was designed to create a stronger, more durable soldier. Developed by Berkley Bionics in Berkley, Calif., the HULC is a wearable robot exoskeleton for the legs. It enables the user to carry up to two hundred pounds on his or her back over long distances and harsh terrains. While the HULC is not a full body exoskeleton like the Raytheon Exoskeleton, it does provide one distinct advantage: the HULC is the only wearable exoskeleton proven to reduce the user's oxygen consumption, giving the soldier greater stamina. The HULC weighs 53 pounds and is battery powered, but can be equipped with a generator that lasts for three days. The only problem: the generator weighs 85 pounds, a big chunk of the robot's carrying capacity.

4. Honda Experimental Walking Assist Device

Saddle up boys and girls, it's time for a new breed of walking horse. The Honda Experimental Walking Assist Device is a robot exoskeleton for the legs, designed to reduce the strain of walking for the elderly and those with mobility problems. Essentially a chair with legs, the Honda exoskeleton allows users to sit down in a saddle-like seat and strap their feet into two shoes attached to artificial limbs. The seat supports a portion of the wearer's body weight, reducing the strain to joints in the knees, ankles and hips. While the device is expected to improve mobility, running a marathon in one probably isn't a good idea, since the lithium ion battery (a more powerful version of the cell phone battery) lasts roughly two hours at a pace of 2.8 miles per hour.

5. MIT Exoskeleton

Designed to use less power and weigh less than similar robotic devices, the exoskeleton developed in Cambridge, at the Massachusetts Institute of Technology, is another wearable robot for the lower body. The purpose of the exoskeleton is to help people with heavy loads to carry on their backs (hikers, soldiers, students with too many physics textbooks) lighten the load. Unlike other robotic exoskeletons, which can require up to 3,000 watts to power, the MIT exoskeleton only requires one watt. However, the device does interfere with the wearer's normal walking motion, which causes the user to expend more oxygen than he or she would without the device.