Advice would be appreciated!

I say just keep doing what you're doing. Getting exercise is important, but masturbation is not. Besides, masturbating can be done in a variety of positions.

 

You're right to be cautious, since our bodies have an incredible sense of memory. When we assume a certain pose at a certain time or in a certain mindset, our body often assumes it's to perform a certain function.

It may be useful to say to yourself as you get into the position to start the curls, "this is for exercise and only for exercise." You may even need to say it to yourself repeatedly as you perform the movements. Your body may initially go into arousal mode, but should quickly understand your new intentions and adjust accordingly.

And, of course, if you stop using that position for M, your body will understand that you now only use that position or series of muscle movements to exercise, not for anything else. It may take a while to get into the swing of things, but it will happen eventually. All the best to you