I am not a trekking pole advocate. Folks may counter this by saying I do not know how to properly use them, and this may be true. If a hiker has a physical limitation, they may be of benefit. Additionally if a hiker is expert in their use and maintains a natural walking motion and stride, and correct posture trekking poles maybe advantageous.
The bottom line on trekking poles is the fact the hiker will expend more energy when using poles. This is due to the fact that body and pack weight will be transferred from the legs to the arms and upper body, using muscles that are much less capable of carrying repetitive loads than the leg muscles. If a hiker needs to additional upper body muscles to assist in hiking, then perhaps the hiker should analyze the root cause of this problem — their legs are not conditioned enough to hike. All of this means the body is going to consume more calories when hiking with poles, than without. And long hikes typically burn more calories than we replace. If a person is in good physical shape, then it simply does not make sense to run a calorie deficit, unless it is a short hike.
Most pole users report that poles help them hike down-hill without damage to joints. Unless they have damage to their joints, I am not buying this benefit. I have been hiking downhill for nearly 50 years, and have no joint problems. I rely on my legs to act as springs when going downhill, not poles that force me to change my stride and posture. For my comments on how improper stride negatively impacts muscles, joints, tendons, etc. see my post on minimalist footwear.
Trekking poles do assist with balance, especially when fording streams or rivers. But then one could simply pick up a stick to do this. Also I find when crossing these obstacles that one pole works better than two for me.
Pole users also report they have less swelling of hands when using poles, because the are constantly moving their arms. Hmm… just swing your arms when hiking, that is the natural way most people walk.
Now one benefit of trekking poles I will agree with is the fact they make good tent poles when using a tarp shelter. Okay, just strap tent poles to your pack — but wait… many hikers are consumed with their spreadsheets and deducting the weight of tent poles from the sheet’s base weight and transferring it to items carried seems to be a huge motivator in the UL hiking community — the my pack weighs less than yours mentality.
I will admit that I often hike with a single staff. But I will state that it does not enhance my actual hiking. It does act as a functional tool to erect a tarp, move rattlesnakes from my path, and other miscellaneous tasks. But it is not a necessary item.