A bulk loader was loading a bulk trailer. EE began opening the center hatch of the bulk semi. As EE was opening the hatch EE found all the hatch latches to be difficult to open but EE was able to open the first four. On the fifth latch EE pulled and felt a strain in right shoulder. After EE felt the strain in EE's shoulder EE used a hammer to pry the 5th and 6th latch open.