Klassen Harness Fitment and leg numbness
Numbness in the legs is a common problem with Klassen harness fitting and I’m surprised that more people don’t know about it. I’ve developed strategies for how to prevent that numbness and tingling sensation in your leg, after reading about early Klassen harness owners who had numbness in their leg that even in a few cases lead to them falling in the rig. Perhaps that old history isn’t being talked about as much as the Klassen harness has become more mainstream.
The issue of numbness in the legs is a common one amongst those who use Klassen harnesses. Where the harness rides is over a very important joint - the hip socket - and around that socket joint you have a significant amount of blood vessel crossings and nerve crossings to get the blood and nerve signals down your leg. The harness by its nature wants to tip forwards on your body, and if the harness is not in the right place on that joint, the bottom edge of the harness will put a line of pressure onto those blood vessels and nerve pathways and pinch them off. This generally can be identified at first by a coldness or tingling in the front surface of the thigh closest to the rig - that is the thigh that gets pinched the most. The coolness or tingling will slowly lead to numbness, until the entire leg “falls asleep”, which can cause a fall if not checked.
One significant cause of this is that the harness may be too low on your pelvis. If you feel this tingling, numbness, or cool feeling in your leg, stop and immediately adjust the shoulder straps to be a bit shorter. These are small adjustments - can be as little as a 1/4”, probably no more than 1”. What you will find is that especially with heavier loads, as you shorten these straps, you’ll get to a point where you begin to feel back muscle activation again, like you’re wearing a front mount vest, or tightness in your shoulders as the shoulder straps are now carrying more weight than they’re designed for. That may mean you’ve gone too far.
It’s a balancing act to get the strap length exactly perfect, and it can change season to season as your body gains and loses weight, the foam compresses more in heat versus cool weather, and even as you change loads - a heavier rig will tend to dig in more and may require you to shorten the strap.
Get used to checking in with your leg - I found that I as I was getting the length worked out would periodically reach down and touch the surface of my left thigh (the one closest to the rig for me, a regular operator) and see if it had feeling in it. If it felt cool (not to the touch, but had the sensation of coolness) or if it was tingly or if it wasn’t registering my touch, I would quickly shorten my straps a touch, and generally things would improve.
Let me know if you have any questions - I’ve owned 3 Klassen harnesses (still own 2!) and have spent a lot of time with their fitting and am happy to answer questions if anyone has them.