A collapsible training unit for cyclists comprises a frame made up of three sub-assemblies (10, 11, 12) pivotally connected one to the next. A front sub-assembly (12) supports the front forks (30) of a bicycle (from which the front wheel has been removed) and a rear sub-assembly (10) carries rollers (10) on which the rear wheel (35) of the bicycle rests. The frame is adjustable to vary the distance between the support for the bicycle forks and the rollers in order to accommodate bicycles of differing wheelbase, and the adjustment to the frame is retained during collapse and erection of the frame.