I have a real issue with Camelbaks…
I suffered with back spasms for a few years to the point when sometimes I’d bend down to pick something up and couldn’t stand up again, which got to be a proper problem once when I was out on a ride at the top of High Street.
Someone mentioned to me that it could be the pack and I had been finding that no matter how much I adjusted the straps the weight would shift to one side whilst riding (it was a Camelbak Mule).
I swapped over to an Evoc Enduro Blackline with a back protector insert. The result was instant. The load was off the spine and central and the straps fit that well it’s like riding with a hug. More importantly 3 years on I’ve not had a back problem since.
Everytime I follow someone with a Camelbak I see their pack off to one side or moving from side to side and I know several other people who’ve had similar back problems and switched over.
PS Don’t bother with the Evoc bladder though, run a Camelbak bladder, that part of their packs can’t be beaten.