The stroke cycles were separated into two phases (contact and recovery) based on total force applied to the handrim, with the contact phase subdivided into periods of propulsive contact (propulsion) and nonpropulsive contact (initial contact and release) as determined by the moment about the wheel axle [ 21].
The propulsion period angle, the angle the wheel moved during propulsive hand contact, was similarly defined during the propulsion period.
Just as an increase in accelerating torque in a motorcycle results in nose-up pitching and reduced weight support on the front wheel, a similar principle applies to accelerating quadrupeds (where the hind leg is equivalent to a spoke of the rear wheel and most of the propulsive musculature is arranged to retract, or pull the leg backwards).
The only known example of a biological "wheel"—a system capable of providing continuous propulsive torque about a fixed body is the flagellum, a propeller-like tail used by single-celled prokaryotes for propulsion.
The horizontal components, due to friction between the wheels and the ground, including rolling resistance, are in response to propulsive forces, braking forces, and turning forces.
"Number Nine," a 16-minute bonbon of a ballet to Michael Torke's propulsive score "Ash," keeps its yellow-clad ensemble and four principal couples wheeling through kaleidoscopic patterns that surprise as they smoothly crystallize and deliquesce, sometimes matching the musical rhythms, sometimes working against them.
The A.V. Club Christopher Bahn gave the album a B- rating, calling it "heart-on-sleeve and icily detached at the same time"; however, Bahn felt that "the lack of a propulsive single... as well as an overabundance of instrumentals, suggests a band that's spinning its wheels".
That anxiety is propulsive.
This thing is extraordinarily propulsive".
