Contributed by Adele Frizzle
Mushy, swampy, snowy, or uneven ground, several creek crossings, lots of elevation gain and loss, even a previous leg injury - these are all conditions that would make me choose poles. If I anticipate a flat or short section, I'll leave the poles with support.
However, distance does play a role. Long treks (30 km+) make for very sore feet and can aggravate a pre-existing injury so the poles really help. They say you can go up to 30% further with poles because they bear some of the weight and your legs are a lot less fatigued. If you're carrying a lot of gear, they can really help - especially when negotiating footing in tricky terrain.
If you're considering poles, I recommend training with them. Find out what height works best for you and mark it. I like my hands a little lower than my elbows but it's a personal choice. I just find my hands don't go as numb and my shoulders don't get quite as sore in this position. You may also find using one pole just as effective, especially in terrain where you need to scramble or if you're the navigator and need a free hand for compass work. There is a current raging debate on that subject, as some people consider the use of one pole imbalancing and causing musculoskeletal injuries.
Remember, if you're using poles, you're reducing the wear and tear on your legs but increasing the demands on your upper body, especially upper back and shoulders. Also, your heart rate will probably increase, although your speed may not, at least while you're fresh. In the long haul, they may help you go faster and further.
A little off topic but helpful nonetheless - your poles are a great place to wrap a little duct tape - just in case. And if you're considering buying poles, I recommend ones that have a slightly angled handgrip for a more natural feel and less stress on your wrists. Lastly, make sure your pack has somewhere to stash your poles when you need your hands free.