4. what are three ethical safeguards used in psychology research? describe each.

First of all, the participation of any human subject must be voluntary. The participants should be there willingly and not under conditions of threat, coercion or bribing.
Secondly, before starting the experiment, researchers must obtain an informed consent signed by each participant. An informed consent is the process of informing the participants about all the techniques and procedures and all the probable risks and dangers. After the participants are informed in detail and have all their questions answered sincerely, they should sign the informed consent form. 
Thirdly, researchers should keep each participant's confidentiality. Any information or process that could identify the participant should be kept secret.

The person who utilize the progression principle will keep adding the difficulty of the exercise that he's doing, while the person who does not, will only stay stagnant.  the person that utilize progression principle, will get a stronger endurance because now his body is conditioned to do harsher routines.{the answer was already on verified)