I run a lot of trail races, and quite often find my arms and shoulders are a bit sore afterwards; especially on the longer races. I think it is from a combination of using them for balance on the corners and downhills, aka flailing wildly. Just my theory at least.

That would make sense. Any ways of dealing with it or preventing it? or should I just get used to it?

---

______________________________________________

A thought:

Years ago I would notice that after races, my arms/shoulders were sore, but could never figure out why.

Then one day I did a V02 max test and a friend recorded some video from it, and I noticed how low my arms were hanging. That's when I realized that me letting my arms hang down lower took more energy to move them with my cadence, thus the soreness.

For a while after that, I made a conscious effort to hold my hands up a bit higher, especially while running at a high effort. I've not had any soreness in the years since.

---

---
KyleKranz.com
Win a pair of SKORA Running Shoes!

Lift.

My first 3 half marathons were like this. 100% the day after, my arms were more sore than my legs.

It went away in the last 2 years. 2 things changed:

1) I started bench press and am about 3x as strong
2) I ran a lot more races and have better posture now

Cannot say for sure which one fixed it ;) Maybe both?

Lifting is a waste of time. Just run trails more.
You use your arms more on the trails: pumping to propel you up the slopes, waving (flailing) them about for balance, possibly carrying a water bottle. Just repeat that stimulus often and they'll get strong enough to cope and you'll be getting in more miles as well!

Lifting is not a waste of time. Also, babes.

This!!

if you're not looking to gain a bunch of mass to have to carry around, look into progressive calistentics. A ton of varying excersize you can do, plus most of them don't need any equipment. You can get your strength training in outside, or inside the gym.
I have been working it into my short runs... run a 1/4 mileish, do a set, run another 1/4, do a set... etc.