A South Korean-U.S. team of scientists have bred a "marathon" mouse which can run twice as far as a normal rodent.

Researchers say the genetically engineered animal can run farther and longer than their naturally bred peers, and are more resistant to weight gain.

In lab tests, normal mice were able to run about nine hundred meters before dropping out due to exhaustion. The genetically engineered animals were able to run one thousand-800 meters before they ran out of steam.

The "super mouse" was created by changing a gene that codes for a specific protein, leading to an increase in so-called "slow-twitch" muscle fiber.

Scientists say the findings could be used to help people with muscle or weight problems, but also acknowledge their studies could be abused by athletes.

The findings have been published in a paper posted in the open-access journal Public Library of Science Biology.

The research paper was co-written by Dr. Ronald Evans of the Salk Institute in San Diego California and Han Joong-yeob and Kang Heon-jung of Seoul National University.