A virtual reality computer program simulates the fatigue felt by many cancer patients.

WASHINGTON (CNN) -- Politicians tried out a new computer program on Thursday designed to simulate fatigue brought on by cancer as part of the weekend's events leading to a national rally against cancer.

"The machine does a very good job of making it hard for you to move around the room," said Sen. Connie Mack, R-Florida, a melanoma cancer survivor.

The virtual reality computer program is aimed at health care providers who work with cancer patients.

Most people stricken with cancer suffer chronic fatigue. Developers of the device said doctors can better treat cancer fatigue by using this device as a gauge.

"We're trying to bridge the gap between health care providers and cancer patients," said device developer Dr. Jonathan Merrill.

Machine uses are seated in a special chair and outfitted with special gloves and headgear that are electronically connected to a computer.

The computer program has users walk around in a virtual room.

Through a viewer inside the headgear, interactive technology allows the user to "see" the rooms of the home as if he or she were actually there. The user performs the act of "walking" through the virtual home by moving pedals located in front of the chair.

The computer program is designed to make all movements inside the virtual home more difficult, to simulate fatigue experienced by most cancer patients.

The National Cancer March will hold a candlelight vigil on the Lincoln Memorial Friday night and a rally on the National Mall on Saturday. The event, featuring speakers Vice President Al Gore and the Rev. Jesse Jackson, is billed as the first-ever massive demonstration against cancer.