Yes and yes, with a degree in sports psych.
Ah, the argument from authority.
Day 1 in a 101 class- rah rah halftime speeches have no measurable affect on athletes.
Why is there sports psychology at all, then?
For every one of your 2 examples, there are 1,000,000 of someone giving that speech, then having their team continue to get their ass kicked in the 2nd half.
So, your better approach would be to tell the team:
Sorry, lads, but sports psychologists maintain that
nothing I say can motivate you to play better.
I can envision the team captain standing up:
Hey, guys, the coach must be trying some of that
reverse psychology bullshit on us! Lets do it!