This position requires you to lift boxes up to 50 pounds. Are you physically capable of this task?

Many jobs require some intermediate to heavy lifting. At 7-eleven there will be new stock coming in all the time--some light and some heavy. Assure the interviewer that you are physically capable of assisting with the receiving of stock. If you do have limitations, this is the time to disclose them. You do not need to get overly personal with health issues, but you do need to be upfront and honest. Focus on what you CAN do versus what you cannot.