verb (v)

• make strong or stronger(verb.change)

  Example:
  This exercise will strengthen your upper body.
  Strengthen the relations between the two countries.
  

  Synonym:
  beef up, fortify
  

  source: wordnet30
• gain strength(verb.change)

  Example:
  His body strengthened.
  

  Antonym:
  weaken
  

  source: wordnet30
• give a healthy elasticity to(verb.body)

  Synonym:
  tone, tone up
  

  source: wordnet30
• To make strong or stronger; to add strength to; as, to strengthen a limb, a bridge, an army; to strengthen an obligation; to strengthen authority.(verb)

  source: webster1913
• To grow strong or stronger.(verb)

  source: webster1913