The phrase stand up straight is not a reference to his posture but to the fact that he should stand up fully on his feet rather than lean against something or perhaps crouch over. In some languages this may be equivalent to “stand up fully” or “stand up to your full height.”

On jumped up and started walking around see 3.8.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on The Acts of the Apostles. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .