not just standing up,you have to do some lifting while your dropping the full tray mail or tie the full sacks and throw it in container,but you have to do it on rotation,come this summer season it will be too slow and the 36 to 40 hrs a week your enjoying will be cut into 20 to 30 hrs a week and it all depend on the volume of the mails that's coming in.it is a better routine work out while your working, you dont have to go to a gym. i"ve been a pse mail processing clerk for 3 years and doing all kind of stuff what ever the supervisor needs to be done,,as what the title says PSE ,,,Postal Support Employee,,,sometimes it is POstal SLAVE Employee,,good luck guys