They're like Underoos for big boys -- but unlike the childhood version covered in Spiderman graphics, these really do give the wearer extra powers.

While on long patrols, often in rugged terrain and extreme temperatures, U.S. service personnel are regularly required to carry a crazy amount of weight. Warfighters often lug 100 pounds or more in body armor, equipment and other essentials.

And as the weight increases, so does the rate of joint and soft-tissue injuries.

Designed by DARPA, the military's advanced research arm, the Warrior Web undergarment will help prevent injury, reduce fatigue and improve endurance -- and the next phase of testing is about to kick off.

Warrior Web

A sort of diver's wetsuit with a full range of motion, Warrior Web will be a lightweight yet flexible stretchy web suit that comfortably fits beneath a uniform and body armor.

Adaptable to different body types, the suit will be a breathable material to avoid increasing body heat and to allow moisture to pass through.

The hope is it will weigh less than 20 pounds -- but the suit will be designed to compensate for its own weight as well as the heavy load typically carried by a warfighter.

Embedded with a web of miniature sensors, the suit incorporates biometric feedback that could provide internal cues to the soldier wearing it to reduce injuries.

How does it keep warfighters walking?

Ankles, knees and the spine are particularly vulnerable to the physical stresses placed on the warfighter.

With the additional weight typically carried, tactical activities like running, crawling and squatting further increase fatigue, can erode performance and reduce the warfighter's ability to resist injury whether chronic or acute.

The Warrior Web program aims to develop technologies that will reduce this strain.

Not only will the suit directly reduce injuries, Warrior Web will augment warfighters' muscles to dramatically improve endurance and effectiveness.

To improve performance, the suit could for example stay flexible and then stiffen to provide support where and when a soldier needs it most

Say a joint is at risk for injury, the suit may sense the threat, alert the wearer and then stiffen and relax at key body joints to help prevent injury.

Or say the sensors detect fatigue creeping into specific muscles putting the soldier at risk for reduced performance and injury? The suit will sense the risk and then using its web system, it will adapt and activate shifts to appropriately support the fatigued area. It may even trigger vibrations to soothe the muscle.

The state of the art suit will accomplish all of this using less than 100 watts of electric power from an in built battery.

Next phase of testing

Currently, DARPA's program is in the first task phase, called Warrior Web Alpha; it's developing essential technologies such as injury mitigation, adaptive sensing and control, and the interface between suit and human.

The U.S. Army Research Laboratory Human Research and Engineering Directorate has been conducting several months of tests on a prototype.

Sensors collect force, acceleration and muscle activity data while a camera captures gait and balance shifts and another device tracks oxygen consumption.

In several weeks, the second phase, called Warrior Web Bravo or Task B, will kick off and focus on producing a suit that integrates these technologies for real-world testing.

From U.S. Olympians using Fastskin3 to increase swim speed to suits that reduce drag for runners, athletes have been successfully using similar technology to improve performance.

Harvard University's The Wyss Institute won an initial $2.6 million contract to work on Warrior Web.

Ballet dancer turned defense specialist Allison Barrie has traveled around the world covering the military, terrorism, weapons advancements and life on the front line. You can reach her at wargames@foxnews.com or follow her on Twitter @Allison_Barrie