Stationary bike on balcony

I own my place and put a silent magnetic stationary bike on my balcony to use since I have a kid and when I'm looking after him I can't get to the gym. About 100ft away is another mansion block the same height which has outside walkways to the apartments which directly faces my building and my balcony.

I've had some weird looks from people as they walked to their apartments over the past 9 months, but no complaints. I should clarify that I've deliberately positioned my bike so it faces away from their walkway.

Anyway, today someone went in their apartment and then popped their hand out of the door holding a phone and took a picture of me. I only saw it because I saw the reflection in the balcony windows as I was looking at my kid inside the room.

I don't think my bike breaks my apartment rules and there's no law against using one's own balcony for exercise as far as I know. What gives? Should I expect complaints soon?

by MutedCalligrapher967