You do not need to be a triathlete to succeed in trekking. What you do need is a deep reserve of strength and stamina rather than speed. Eventually you want to be training uphill with 5 kg depending on your size, strength and fitness goal. If you are super-strong at home, you will find your trek much easier.
In your training you want to be able to comfortably walk uphill with your pack doing 300m vertically per hour for 1 hour minimum. As your fitness and strength improves you should be able to do this for 6 hours. We do not suggest you need to do this every day, in fact you would be better training for 30 min – 1 hour a day, 3 times a week.
At least a month before your trip, it can be very helpful to go out on one or two weekends and do a long training walk for say 6-8 hours. Or consider training on consecutive days to get the feel (and endurance boost) of working a tired body.
We do not recommend intensifying your training immediately before the trip; it would be a huge disappointment to injure yourself at that late stage!