We all spend a lot of time at our desks and many of the ailments that come with this sort of work are preventable, if you follow this advice on DSE posture and taking breaks.
Do not sit in the same position for long periods of time, make sure you change your posture as often as is practicle. But ensure you are in the correct position for typing as detailed in your DSE Training.
Some movement is desirable, but avoid repeated stretching to reach things you need, move them closer towards you.
Make use of breaks from your screen, eg. to do filing or photocopying to change your focus and viewing distance. Ensure you blink regularly to keep the eyes moist.
Take regular breaks from repetitive keying and mouse work.
If there are no natural breaks in your job, your manager should plan for you to have rest breaks. Frequent short breaks are better than fewer long ones.
For further guidance on how to help yourself when using DSE visit: https://staff.shu.ac.uk/healthandsafety/DSEGuidance.asp
Ensure you have completed a DSE Assessment within the last two years. Your local DSE Assessor will be able to check when you last completed one.