You can clearly tell the difference between the actors and their stunt-doubles particularly during the first couple of episodes when the rangers are fighting Jack and Z.
In both "History" and "Wormhole" Commander Cruger erases the Rangers' memories because he believes them knowing the future would be dangerous, yet in "Messenger" he has no problem with Boom getting a radio broadcast from the future, and in "Samurai" an alien is brought from the past and they don't even try to erase his memory. Also, in the end, when the Omega and Nova Rangers return to their time, their memories do not get erased.