内容简介：
Six Titles Written in the Exciting Spirit of the Eco Challenge These Titles Will Fascinate and Exhilarate Middle School Readers Ultra pursuits--recall all the attention given to the climbs up Mt. Everest--have long captured people's interest and awe. In recent years, young people have become more and more interested in sporting events that push people to their ultimate limits. Highlighting both the risk-taking and the safety precautions involved in the sports presented, these books also chronicle the personal and physical challenges these unique athletes confront. The ultra sport of marathon skiing involves cross-country skiing, and it means pushing yourself to ultra fitness, ultra performane, and sometimes ultra pain. Take a look at this amazing world of snow, skis, and determination. Stiefer provides all the information you'll need to have a sense of what it's like out on the slopes