Rebounding is recommended to help with lymph movement.
Not long ~ 5 ins or so. Do recognise Resting plays a fundamental role in the fast repair process.
Exercise has been much debated here. My dime's worth:
Exercise amounts etc depend on your health and your fasting history.
On my first fast I could do very little exercise.
After a short fasting history I can't stop myself.
Very rarely do I slow down during a fast these days.
Some appear to need all the rest they can get, others
exercise moderately, and others keep their regular regimes.