To undertake a trekking trip comfortably, a reasonable level of fitness is recommended. It is better to build up over time rather than undertake last minute training before you leave for your trip. It is recommended to get your body used to a reasonable level of exercise so that the impacts of trekking and increasing altitude are not felt so much.
At the same time, you do not want to push yourself so much such that your immune system is under too much stress, so please do not start an ‘Olympic style’ fitness schedule for the purpose of training for your trip. You want to peak during your trip, not at the beginning. (As a guide, sometimes we say it is better to be 85% fit before a trip so that you can peak toward the 3rd quarter of any trip).
Note: The above information is provided as a guide only and should not be relied upon as suitable training for each and every person for each and every adventure travel activity in which you may propose to participate. It is recommended that you seek medical advice from your own health care professional before commencing any fitness routine.