It's an odd thought that a 'hobbler' must have been one of the fittest men alive, in the days when it was a common term. Eily Gayford, one of the original IDLE WOMEN, describes 'hobbling' as the process of running ahead to get the locks ready, and hobblers in the old days would sometimes be intinerant men available to hire. It was a term restricted, apparently, to the Midlands, and particularly to the Birmingham & Worcester canal.
The term is little used these days, and the process is known almost universally as 'LOCKWHEELING' - perhaps because it's more effectively done by bicycle - especially where the locks are further apart.
Whatever the nomenclature and etymology, the process of running/cycling ahead is a wonderful exercise. I call the English canals 'the world's greatest gymnasium'. You get the aerobics from chasing ahead of the boats, and the muscular workout from DRAWING THE PADDLES and opening and closing the gates. And all in the beautiful green countryside. If it's raining, and it's not too cold, then dammit, so much the better! You work up a thirst and a jolly good appetite, too, which is 90% of the purpose, naturally. You work up the thirst to cool down. On the English canals it's the greatest of virtuous circles. With any luck, the only real hobbling you'll do is an unsteady one back to the boat at pub closing time.
But the real origin of the term is perhaps more romantic and more historic, predating even the canal era. A hobiler, in medieval times, was a man contracted to maintain a horse ready for war. He was, in short, what we, these days, would in England call a territorial, and in America a reservist. The term comes from the same root as 'hobby horse'.
I guess that 240 years ago in the Midlands, the originally hobbler, the man who managed the horse, would also be the one who'd rush ahead of the horse and get the lock ready.