How physically demanding is being a library assistant?

i had to quit my last job that was part time and retail due to the prolonged standing and difficulty of putting up heavy freight. i can deal with some physically demanding stuff but i need to sit for about an equal time as i stand for health reasons.

i managed to get an interview to be a library assistant after looking for a few months (yay!) but before i go in for the interview i wanted an idea of how physically demanding the job was. do you have to stand for prolonged amounts of time (think more than 2 hours)? how often can you sit and for how long?

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