This does not mean anything overly strenuous. Something as simple as a daily walk can make a huge impact on your health.
Proper nutrients allow the body to repair itself easier. Eat organic, unrefined foods and drink at least eight glasses of pure water every day. Avoid drugs, whether recreational or prescribed, including alcohol and caffeine.
Are you sitting up straight as you read this?
Avoid sleeping on your stomach, it twists your neck; avoid the fetal position; it reverses your spinal curves.
When you think about the amount of time you use these things each day, it's worth it
This will also help to loosen up the surrounding muscles and prevent injuries
Whether in a car or at a desk, stretching regularly will help to keep you from tightening up or injuring yourself further.
There are many "hands-free" devices that can be used to avoid this posture.
Remember to carry it over both shoulders to balance the load (if possible). Keep your wallet out of your back pocket when sitting, especially when driving.
Especially if you are ill, under a lot of stress, pregnant or in an accident or trauma. Remember, it is much easier to prevent a problem than to correct one.