There are so many factors that can affect worker productivity. Overall, productivity can be improved through mechanization. A worker with a backhoe will be much more productive than one with a shovel.
However, if you are talking about productivity change without changing equipment, there are still factors that can matter. Perhaps the most important one is motivation and morale. Workers who are happy and motivated will be much more likely to be productive. Organization is also important. A workplace that is well organized and has streamlined production processes will also be more productive than one in which work is done in a haphazard way.
Keeping equipment constant, I would argue that motivation and organization are the most important factors that affect worker productivity.