Though physical fitness is an important part of any outdoor activity, you don’t need to be an athletes or marathon runner to enjoy the trekking in Nepal. Physical fitness is probably less of an issue at the start than you might think. Most people of good fitness for their age can complete our trek. Trekking is about taking your time, setting your own pace and enjoying the experience to its fullest. Most first-time trekkers are concerned that they won't keep up, but soon discover that a steady pace will have them in camp well before they would have expected. These treks are not training runs for the fit, but walking holidays for people of all ages.
Since you will be starting with short treks and working your way up, your fitness level is likely to build along with your experience. An enthusiastic attitude is far more important at this stage in the game. You can be the fittest person in the world but if you have no genuine interest in trekking it will not become a long term activity for you. Nevertheless, it cannot be understated that if you were physically trained before your trek, you will enjoy the experience a whole lot more. It should also be noted that almost every trekker in Nepal has prepared physically and as such, has made a commitment to the trek ahead. By under preparing, not only are you robbing yourself of an enjoyable experience, but also potentially letting down the team of people you will be trekking with. Trek training by definition means that you will strengthen major body muscles (in particular legs) and trains your cardiovascular system. So raising your heart rate during a training session is imperative!
Below is a general guideline as to what amount of exercise we recommend you undertake to prepare for the trip. Every trek has a big "uphill" somewhere and no treks are easy, but a mental attitude that allows you to relax and take your time is the best way to trek. There is no single fitness program to suit every person. We are all different. There is no better training than trekking itself. Get a day pack on and get out there as often as you can. But if, like most of us, your free time is limited there are other things you can do to fill the gaps.
We consider this to be a moderate trip and on a moderate trip you will be walking for six to eight hours per day, at altitudes up to a maximum of 5,600 meters. At least three to four months prior to departure you should involve yourself in at least one hour of exercise three to four times per week. Walking, jogging and cycling are excellent forms of exercise, so long as you are strengthening leg muscles and building stamina. Bushwalking is also great. If you can manage a couple of valley floor to ridge line ascents per bushwalk, you will cope with a moderate graded trek. Speed is not the essence; stamina, confidence and continuity are.
However, if you are planning to join a commercial trekking or mountaineering expedition you will need to develop a high level of fitness so that you can comfortably and safely endure several weeks on the trail.