What energy changes take place when a person walks up a staircase?

When a person walks up a staircase they move upwards, against the force of gravity, given that the force of gravity acting on a person is their weight e.g. 600N. Therefore the person’s chemical energy store is transferred to the gravitational potential energy store when they reach the top of the stairs, where they have moved a vertical distance of 5m, from the floor. Given that the distance must be in the line of action because weight (force) is acting vertically downwards only the vertical distance is relevant in this example.