5. Strenuous: Full-day hikes (9-12 hours), mountainous terrain (up to 5,000ft Elevation). Repeated elevation gains and losses (hiking up or down 3,500-4,500 feet) on most hikes. IMBA Trail Difficulty: Very Difficult. Snowshoe hiking for 4+ hours, with little breaks. Cross Country Skiing for 6+ hours with little breaks.