Before revision:  We integrate an experimental and theoretical framework to connect mesoscopic measurements of nonequilibrium properties to the underlying molecular-scale force kinetics . Our results show that force generation by myosin-V drives the cytoplasmic-skeleton out-of-equilibrium (at frequencies below 300 Hz) and actively softens the environment. In vivo myosin-V activity generates a forceof F \sim 0.4 pN, with a power-stroke of length \Delta x \sim 20 nm and duration \tau \sim 300 \mus , that drives vesicle motion at v_v \sim 320 nm/s.
After revision:  We integrate an experimental and theoretical framework to connect mesoscopic measurements of nonequilibrium properties to the underlying molecular-scale force kinetics in-vivo (motor force, power-stroke of length \Delta x \sim 20 nm and duration \tau \sim 300 \mus , that drives vesicle motion at v_v \sim 320 nm/s.