This is a very frequently asked question.
You can use Nordic Walking Poles for trekking as well as for Nordic Walking; however you can not use Trekking Poles to perfrom Nordic Walking - therefore I suggest you get yourself a pair of Nordic Walking Poles.
Let me explain to you in more detail.
Nordic Walking Poles come with a specially designed wrist strap. Being strapped in means it's easier to apply pressure on the pole as you simply push down your arm. (if you used ordinary poles which come with a loop, you have to hold on to the grip and are therefore limited in how much pressure you put on the pole).
So - comfort wise, but also benefit wise I recommend Nordic Walking Poles (with the proper strap). Also look out for the detachable wrist straps of LEKI and ONE WAY poles.
A lot of trekkers use adjustable poles. What's that all about?
As trekkers often just use poles when they go downhill and not when they're on the flat or going uphill they wanted poles that can be stored away in the backpack - fair enough.
However, by realising that poles also assist on the flat and especially when going uphill, the poles are in use for most of the tiome and don't need to be store daway any more.
Now - adjustable or fixed length poles? Quite simple!
When looking for a pole you look for quality, strength, comfort and price.
Fixed length poles are stronger - one piece is usually stronger than two or three pieces.
With fixed length poles there is no adjustment mechanism that can wear out.
Good quality fixed length poles are cheaper than good quality adjustable poles.
Adjustable poles have the advantage of being collapsable which makes it weasiy to take them with you in a backpack or when you travel (This applies moreso to the three piece pole which collapses down to 67 cm).
Most adjustable poles are made from Alloy which is a very soft (and cheap) material, meaing the poles bend easily. Fixed length poles come with carbon composites or 100% carbon shafts at a relatively good price.
So make your choice. If you're looking for more information visit the Nordic Academy website.
All the best
Yours in health