Productivity is defined as the quality of being productive of the ability to produce. Being productive is defined as being capable of producing. And now too actually get to a meaning; to produce means to actually create something or to cause something to come into being, occur or exist. This can be done through either physical or mental effort and the output may be physical or intellectual.
You can produce thoughts and ideas. Or you can produce manufactured goods. At night you might produce dinner when you cook and in the morning you might produce clean teeth when you brush them. You can produce a vacuum by removing what should be in a space (either physically or metaphorically). You can produce art by painting or humor with a joke.
Production may result in the creation of individual intellectual ideas or entire processes and systems.
In terms of ergonomics productivity refers to the measure of how much you can get done within the scope of your working time table. How many widgets you can make in an eight hour shift shows how productive you are.