With a tap, someone in my Body Attack class commences their workout by warming up a forefinger on my shoulder.

I turn to see who has busted the cardinal rule: Make As Little Eye And Actual Contact With Fellow Exercisers As You Can.

It is a Hong Kong woman wearing an aubergine T-shirt which her face will soon match. Yes, reader, I am being harsh. It is deserved.

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"Would you move forward?"

It is 10.59 and the Body Attack class is due to start.

I am not late. I slipped down the side, judged there was sufficient room for an extra person and inserted myself in the Lycra-clad cluster. In the process, it seems, I crossed a territorial boundary. This is Her Space.

If you don't do group exercise classes, let me explain. Class space is like airspace. The instructor is magnetic north, everyone aligns themselves to him or her.

People have their position, and the dead-reckoning used in air navigation is ambiguous compared with class-space precision.

The issues of Your Space brings out possessive behaviour. Waiting outside a class, people jostle for pole position. When doors open, they sprint in and thrust whatever they can on the floor, to establish a sweaty settlement before going to collect any equipment. If a mineral water brand had the logo "I AM HERE," their bottles would sell out in Hong Kong.

Given this woman is behind me, and the class involves high-kicking, I can see it's not going to be a relaxing experience. Action cinema is HK's greatest export.

There is no reason she won't restage the latest Wong Kar-Wai film and engage in martial moves to settle our dispute.

I dart over to another space. During the class, I make faces at her, which in a Body Attack class could be easily excused as expressions of exhaustion.

The following week, I arrive early and stand poised on The Space. She arrives five minutes later. She is not pleased. Half-way through, when a track requires running forward, she brazenly elbow-thwacks me as she passes.

Thoughts grow of retaliation. Pinging her so-80s headband? Racing too close during the running track? Or actually tripping her up and then listening as she tells the instructor a big girl did it and ran away?"

I walk home, having resisted all options, and get caught up in one of the many demonstrations in Hong Kong.

The crowd marches slowly, it is a good cool-down pace and the combination of body politic and Body Attack makes me think. Had I been a victim of just another global case of Class Space Rage? Or was there a political dimension in the woman's response? Right now Hong Kongers are very touchy about jurisdiction over territory.

Just in case, I seize an anti-Beijing placard. Less meddling from the mainland might mean everyone in HK has a more nonchalant attitude to sovereignty over their stomping ground.

Holding it aloft, I find, also tones my triceps.