What is the meaning of keep up?

verb

• Maintain a required pace or level.
  • usage: "He could not keep up and dropped out of the race"
• Lengthen or extend in duration or space.
  • usage: "We sustained the diplomatic negotiations as long as possible"; "prolong the treatment of the patient"; "keep up the good work"
  • synonyms: prolong, sustain
• Keep in safety and protect from harm, decay, loss, or destruction.
  • usage: "We preserve these archeological findings"; "The old lady could not keep up the building"; "children must be taught to conserve our national heritage"; "The museum curator conserved the ancient manuscripts"
  • synonyms: conserve, preserve, maintain
• Keep informed.
  • usage: "He kept up on his country's foreign policies"
  • synonyms: keep abreast, follow
• Prevent from going to bed at night.
  • usage: "The anticipation of the trip kept the children up all night"; "I kept myself up all night studying for the exam"