The title pretty much says it all. I've started going to the gym semi- regularly and doing some fitness classes, like spinning and full body workout things. During a spinning class, the instructor came up to me and, without asking me, put his hand on my back to correct my posture. I immediately shook his hand off and told him "Please, no touching. Thanks." He looked irritated but left me alone. He never came to my bike again during the session. In a different class, a female instructor pushed my legs up during crunches, when I physically couldn't pull them up further. I simply let my legs fall and waved a hand to signal "leave me alone." Every time I do this, the trainers look so defeated and almost sad. I get that their job is to make sure everybody gets the most out of the training, but I really dislike being touched by strangers, and even more so when I am sweaty and feel somewhat vulnerable. 

Still I can't help feeling that I'm being childish, since nobody else seems to mind the trainers correcting them. So AITA?