I'm late to chime in... but I see three things in the image that hints at how this was done.
First, I'm noticing that the platform leg on the left side shows two soft shadows indicating a couple of light sources lighting the scene from behind. This is likely providing the ambient light.
Second, I'm noticing that the gentleman's arm produces a very sharp and defined shadow (as does his body onto the arm of the lady, as does the lady's hair onto her neckline). This tells me the that the photography likely used a strobe (high and left). It was a pinpoint light source and it wasn't diffused.
Third, I'm looking at the platform surface behind the lady, where the strobe should be casting a bit of a shadow... and it's not. So the lighting in the back is strong enough (or long enough) to overcome the strobe shadow.
With all those observations, my guess is the couple was illuminated only for a split second by the strobe to "freeze" them for the shot, and the ambient lighting was on long enough to light up the background. We don't necessarily know by looking at the image if those back lights were weak and on for a long time... or stronger and on for less time. But I somewhat suspect the latter because someone walking through the image with the lighting that created the ribbon effect is not visible in the image. When I've done this in my youth, I dressed COMPLETELY in black (a black jump-suit and a black mask) to minimize my being detected by the open camera shutter even in weak lighting.
If the ambient room lighting were turned off while the person created the ribbon effect the couple need not stand-still for the duration of the shot. I suspect the ambient lighting was switched off while the ribbon effect was performed.
I don't know that this is what was done to create this shot (there's usually more than one way to achieve the solution).