You can't do that, you might get hurt!
The following was sent to me by one of the rowers I coach. I love the way kettlebells are seen as primeval wrecking balls of death, the marketing hype doesn't help but his comments about personal training are pretty spot on.
Extraordinary scenes in the gym earlier. I'd got to the DB swings in the suggested workout and thought I'd use a kettlebell instead for comfort and symmetry. Anyway, I get halfway through the first set and one of the personal trainers scurries over to tell me that I can't use the kettlebells without supervision, apparently because if I injure myself whilst training alone with KBs they're not insured. No-one seemed to mind when I was squatting 110kg and deadlifting 135kg earlier in the same session. It seems odd that the gym should be insured for people injuring themselves whilst deadlifting unsupervised but not using KBs unsupervised. I suspect (having discussed it with one of the other members shortly afterwards, who told me that the guy who stopped me uses KBs more than the other trainers) that personal training fees are likely to be the motivation behind it.
Amusingly, just as I returned to my place with a DB to carry on the workout, another member was curling on the preacher bench behind me when the plates slid of his EZ bar and he nearly smacked himself in the head with it. I immediately asked him (loudly, with tongue firmly in cheek) where his instructor was and suggested he obtain insurance without delay.
He's 6'4" and 230lbs. I'm surprised that the trainer had the balls to stop him. The training was a light day but even at those weights it would have been enough in his gym for the other members to be 'freaking out and shit'*
*as Shaf once put it.