During the period 1984-1990, impedance-based thinking emerged as the dominant lens for understanding and controlling how mechanical systems interact with their environment. A key pattern involved modulating limb impedance through antagonist muscle coactivation to stabilize posture, introducing the central idea that stiffness and damping can be actively shaped to manage contact. The era also operationalized impedance control via feedback algorithms to impose a desired Cartesian impedance on a nonlinear end-effector, bridging theory and practical manipulation tasks. Simultaneous force and position control in constrained motion tasks enabled robust interaction with surroundings and foreshadowed modern force–position strategies. Modeling grasp compliance and developing stiffness maps for parallel manipulators provided early design guidance, helping anticipate singularities and controllability issues in complex mechanisms. Overall, the period coalesced around shaping mechanical interaction with the environment through impedance-based formulations and compliant actuation, rather than relying solely on position control.