The dream of mechanical cushioning started in 1984. It was then that biomechanical experiments with the goal of optimizing energy return began. First, Nike designers and engineers added steel springs to a running shoe’s midsole to see if it would improve running economy. A year later, they trialed a multi-layer leaf-spring heel unit to see if they could find the sweet spot of cushioning and stability. Experiments on different hinges and mechanical columns continued throughout the rest of the 1980s.