Footstools have been a common accessory in human living quarters for more than a millennia. They have primarily been used as a way of providing a resting position for the feet when a person is seated. Their main purpose was to provide relief for the tired individual by creating a relaxing position with the feet off the ground.
Think of the black and white pictures of individuals in the 1800s in their living space, (like in this link) and you will likely see a footstool somewhere in the picture. Despite the cramped living quarters in those days, the footstool was a must have furniture piece.
Fast forward to the current contemporary times, and the footstool still finds relevance in the home. Fulfilling its function of providing relaxation for the feet as well as being an adornment in the home. But there has also been an evolution of the footstool to provide ergonomic benefits in the form of a footrest.
Because of the sedentary life of most office workers seating in front of their computers and the posture issues such as back pain and leg pain that this sedentary life causes. Footrests have been growing in popularity in providing relief to these issues.
A well-placed footrest in front of a seated person will align the knees to the hips when they place their feet on the footrest. This alignment forces active seating which leads to better posture and relieves neck and back pain.
This sitting position also relieves the stress on the legs and feet, by aiding blood circulation due to the reduced stress being applied to the soles of the feet. And as millennia of human footstool users can attest to, it is very comfortable raising weary feet off the ground. Enhanced productivity is one of the best side effects of a footrest.