"Inescapable" is the first word that comes to mind. With more than a dozen joints and a full case of muscles, is it any wonder that the neck gets pissy when put into a hyperextended position for long periods? Belayer's neck is probably one of the most common complaints we all hear at the crag. The best remedy is to not belay. The next is to not look up. Braces are a waste of time. Like bike helmets, it's not because they are ineffective, but rather for more ephemeral reasons like convenience or vanity.
Compare the number of people you have seen wearing a neck orthotic for belaying to the number of people you have seen belaying. There will never be a tipping point where these become standard issue, but if you have a crappy neck they will certainly help. Likewise, if you lack the monocular coordination of a chameleon, those funny vision-bending-glasses that enable you to look up by looking down will work a treat. Assuming, of course, that you can get your visual cortex around the concept and not break an ankle in the process.
Without the paraphernalia you will need to shake your booty. Look up. Look down. Bend backward. Lean to the side. Hustle like you have position-related ADHD. Use your eyeball muscles! Position your neck at different angles regularly and only as much as you have to. Optimize your stance such that you reduce the extension factor. For instance, in a cave you can turn around to face out instead of craning your neck to look up and back.
By Dr. J, Senior Contributing Editor, Rock and Ice