First secret for sitting at the desk:
Your abdomen must be pressing in to the desk and the back of the chair upright and pressing in up under your shoulder blades. You're locked in, sitting up straight, hollow in lumbar spine.

Second secret:
Spend some time each day standing up. Put a box on your desk big enough to fit your keyboard and your mouse.

 

Third secret:
Get yourself a Balans Chair.
 Spend some time each day on it. The reason these chairs work to provide low back pain relief is because they eliminate the effect that tight hamstrings and buttock muscles have in stopping you from sitting up straight with the 'S" shaped curve in your spine.

'They' say not to spend all your time on it as it may impact on your knees. Some of the day is good - as it sitting with stomach against desk and standing up.

Fourth secret:
Sit on the floor with legs straight out - particularly if all you're doing is reading.

Secret five:
Do  a few hip crossovers at lunch time.

Secret seven:
Build up your pressups to 30, on the trot. Pressups not only strengthen arms and shoulders but also your trunk muscles, front, back and core. Do Superman and cobra for a minute a day.

30 pressups too much? One night in the gym I watched Valda do 32 'men's' pressups. Valda was 66 years old.