You must encourage them to report a little discomfort, niggles, and twinges so that they can be taken care of immediately. If you think the number of complaints is increasing, then it is advisable to arrange the Manual Handling Training so that they can follow the right posture to carry, lift and push heavy objects.
https://issuu.com/auscaregroup/docs/you_should_avoid_in_time_of_manual_handling_to_pre