Very interesting. It looks like the riders are on some kind of rollers that are somehow connected to the small bicycles that go around that rink. Interesting that the riders seem to have to be held for balance.
"people willing to trade their freedom for temporary security deserve neither and will lose both" Benjamin Franklin
2007 Bianchi 928 Carbon Lugged- SRAM Rival
2005 Windsor Kennett Aluminum/carbon- Ultegra
1983 Raleigh Super Course Steel- Shimano 600
I'm betting that they are stationary and being held because with the (slow) films of the time, and probably no flash, an action shot would have been pretty blurry. TGFD.*
*Thank God For Digital
This is a form of roller racing.
They are being held because the race hasn't started yet.
Same way you see bikes being held in the Team Time Trial start booth.