Physical Fitness is an important factor of any outdoor activity, but you do not need to be an athlete or marathon runner to enjoy trekking in Nepal's Himalaya. Most people of good fitness for their age can complete a trek. Remember that a trek in Nepal is a walking holiday, to be undertaken at your own pace, enjoying the Himalayan panorama and cultural variety. Most first time trekkers are often worried that they might not be able to "keep up", but they soon discover that a stable pace, more than likely slow and steady, taking care not to burn the muscles with lactic acid build up, will have them at their destination well before they would have expected. Treks are not competitions, suffering is not necessary, they are walking holidays for people of all ages, and should be enjoyed. That said, it is true that the fitter you are the more will enjoy it and you will also find you have enough energy for extra activities on the trail.
There are three basic training methods you can use to prepare for a trek in Nepal - aerobic, power and mental. Aerobic training is important primarily because you will be trekking in thinner air:
% Available Oxygen
Altitude in meters
With good aerobic training you will be able to better metabolize whatever oxygen is available to you. You should plan on doing at least one hour of aerobic exercise 3 to 4 times per week for 1 month or more before your arrival in Nepal. Walking, jogging, cycling, hiking and hill climbing are some excellent forms of exercise, as you are strengthening leg muscles and building stamina. Some people in flat areas even train on staircases! When trekking, speed is not necessary; stamina, confidence and continuity are.
Rather than having long, gradually ascending trails, most in the Himalaya zig zag almost directly up, requiring a lot more effort than usual, and can present some problems, especially when descending; they require some serious concentration. Most people think that the biggest challenge while trekking on a high mountain is going up, but it is actually descending that creates the most problems. Tai Chi can be an excellent trek preparation exercise as it focuses not only on strengthening the legs' quad muscles, but also on technique for balance, poise and stepping lightly and safely.
Mental preparation is often overlooked by many trekkers who have otherwise prepared well in all other areas. While trekking may well require a lot of physical effort that we have to be able to deal with if we want to see the remote parts of Nepal, it can at the same time be a deeply moving and uplifting exercise in itself. Trekking in the Himalayas is a relatively safe activity and mishaps or problems are usually minor. However, unpleasant things and personal challenges may occur on a long trek. You might for example have a bout of mild illness, find yourself not sleeping as well as usual, find the trek pace too fast, or slow, there might be number of things annoying or stressful during some part of your trek. So, before you leave to start, think about the journey as much more than just a quest to reach a destination. Try to imagine it as an opportunity to experience whatever happens to you on the way as an essential part of the journey. It really does not matter so much whether you actually reach Everest Base Camp or any other destination. You should be prepared to find joy and fulfillment in all the moments of your trip, including the less pleasant ones that you had not expected. Preparing to keep a very positive frame of mind throughout your trip, along with good physical conditioning, will ensure that you are ready to experience all the wonders of Nepal's Himalayas in the best way.