These trips demand a perfect physical fitness, some previous experience and a good preparation. The trek involves some steep ascents and descents, passing high passes and involving glacier crossings. Usually you will trek 6 to 8 hours a day. Some understanding of adventure travel is important as travel conditions can be tougher than you have imagined. The highest elevation approached is around 5,500m and trekking duration can be 3 weeks or a few days plus or minus.
Annapurna Circuit, Everest Base Camp, Gokyo Peak are still the first line of choices of the trekkers who want to try for the first time a strenuous trek. You have the close up views of the highest mountain on earth and the trails cater lodging and fooding facilities. Annapurna Circuit trekker can take an optional route of un-trodden and wild Tilicho Lake route from Manang towards. A gradual ascent through a green river valley will lead you up to a number of high passes, where you will reach the altitude of 5,416m at Thorong La. Everest Base Camp and Gokyo Peak treks take you to the middle of the soaring peaks and cultures of the Everest region. Makalu Base Camp Trekking in the eastern Nepal and Upper Mustang Trek, north of Annapurna region might interest you if you want to try strenuous treks in the wilderness region.