Fit adjustment and surprise numbness/weakness

So this is going to seem weird, but bear with me.

Ive been riding Tri bikes for about 3 years with no problem in aero for long periods of time. I recently changed my fit which mainly raised the saddle (not sure exactly how much) and dropped the riser about 4cm. Ever since then, EVERY ride, I get numbness, loss of grip strength, and loss of motor control in my left hand. I’ve brought the riser back up in increments, but I still get the numbness. My Chiro and I have narrowed it down to either the brachial plexus being blocked because of the new, lower position, or a nerve having added pressure in my elbow and it effecting my hand.

Other than going back to my old fit, I’m not sure what I can do.

Anyone else ever have anything like this and if so, what was your solutions?


Can you pin down the area of numbness? Whole hand, only the smaller fingers or maybe thumb area? Back or front of the hand? What about your arm? Is it on your forearm or upper arm?

Test that by poking the areas with something dull, like the grip of a tool or similar (not your finger).

What about motor function? Can you form a fist? Stretch all fingers? Can you flex your hand similar to the position while doing push ups for a minute without pain?

To be honest, "partial) “blockage” of the brachial plexus is a severe diagnosis that seems a bit unlikely and would have greater consequences.

As you see there is a lot of things to consider. One common problem is compression of one of the three nerves that supplies the hand, though that is a wild guess as I haven’t seen you in person. That’s why I recommend seeing a doctor, specifically a neurologist. A general practinioner might also do the trick if it’s more convenient and assuming it’s one of the more common causes.

Whatever you do, don’t treat numbness lightly, it’s a sign of (temporary) nerve damage so should be avoided. Switching back to your old fit is definitely a good idea until this is resolved! You can take notes of your current fit and revert any time!

From a fitter perspective, the first lesson here is to always measure the bike before making any changes.

  1. That way you can revert back to it for any reason, especially if the new change is deemed to be undesirable for any reason.
  2. So you can track this and any future changes and at what point the tangential affects change for the better or worse, and you then can look at the range of changes and their impact to learn what does and does not work for you.

In this case, I would revert entirely back to the original setup (if possible since the precise saddle height change may be unknown). The reason for this is that you are experiencing a severe and entirely new issue. So I think heading back to the start and allowing yourself to reset is important. Hopefully that reset will eliminate the issues you are experiencing.

On to the second lesson available here.

  1. Assuming that is true, then you can consider making changes again. But do them with a single adjustment (saddle or pad spacers only), in smaller steps, and then evaluate the impact of that single/small change.
  2. As of now, you had made some very dramatic changes and are now experiencing a dramatic issue. And you don’t know which one or which combo of changes lead to the issue. It’s better to take a slower and more scientific approach now, so you can better understand the issue and how your bike setup drives it.

Lowering the cockpit by 4 cm at a time is a MASSIVE shift. These things have a way of sorting themselves out sometimes as you get used to the new position, but it takes a small step at a time…

And add to that a saddle height increase (of unknown distance) and you get an even bigger effective drop between the saddle and pads. So yes, this was a massive change indeed and I am not surprised at all that it lead to issues. At the very least, a change like this could lead to pure muscle soreness and strain on the body from the new position. At the worst, we seem to see a huge issue.

Reading the fit related answers I would also chime in and focus on changing the fit. It’s bike related and if going back helps then do that! Following Chad’s advice by changing to your desired fit in smaller steps is a good idea for sure!
Still I’d see a doc - but only if changes to the bike don’t help.

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Thanks everyone. The plan is to go back to my original fit and then move forward with adjustments. I knew going in that the change would be aggressive but was definitely a “hope for the best plan for the worst” mentality. Never know until you try, right? Ugggggg


Hi Uni - Yeah its pretty severe. Motor control was way off (its gotten better overnight). The first time it happened the loss of control was enough that I couldn’t grip or open a Gu pack. Numbness was present but I still had sensory input (could tell the difference between a sharp poke and something dull with my eyes closed). The reason we suspected something “higher in the chain” was the extend of the involvement (thumb to all 4 fingers).

Its better this morning so “definitely” just some impingement on the nerve. Unfortunately its something I’m familiar with. Getting sorted out though.

Thanks for all the ideas!

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