Among all workplace injuries, back and neck injuries are easily among the most debilitating. Often, in fact, they are life threatening or can lead to lifelong inability to work and earn a living for oneself and one's family.
Sudden impacts to the back or neck from a falling/sliding object can damage the spinal cord and the central nervous system, and heavy lifting or serious slip and fall accidents can do the same.
The range of severity of neck/back injury can vary. Neck sprains/strains, whiplash, pinched nerves, and herniated discs are common examples. And full or partial paralysis, which can be either temporary or permanent, is on the most severe end of the spectrum.
California workers comp will cover all manner of neck and back injuries if they occurred while you were on the job. This is true even if your "bad back" is the result of repetitive stress at work rather than a one-time incident. Don't assume you can't get workers comp benefits just because your injury's origin isn't immediately obvious - there are ways to substantiate the cause with evidence gathered during a focused investigation.