I’m having fun watching the historical bicycle films collected at CriticalPast, an archival film distribution service.
I see that some of the goofier bicycle inspired exercise machines we see today are nothing new. Check out, for example, this “Rythm Bicycle” promotion from San Francisco in 1936. This “Rhythm Bicycle” uses a treadle mechanism to push the bike and make the saddle bounce up and down while you’re riding.
CriticalPast entitles this one “Several girls sitting on bouncing bicycles.”