Japanese language/customs questions

[Ninja Relaxer]

I've been rewatching old Sasukes, and I was hoping someone here could answer some longstanding questions for me. In no particular order:

(1) Nagano often has his back slapped before a run (usually with a towel covering his back). I assume this is a Japanese custom of some kind, but I can't find any information on it. Anyone know?

(2) Competitors sometimes yell "Sa!" (or is it "Sha?") before attempting a difficult challenge (on Stage 3, for example). Asa Kazuma does it the most frequently; Kawaguchi has done it a few times too. Is this an actual Japanese word with a definite meaning, or more of an exclamation, like "Huh!" or "Hmm," indicating a mood rather than an exact meaning?

(3) Re-watching SASUKE 32 last night, I heard the word/phrase "machika" a few times (majika? mah chi kah?). Urushihara says it 2 or 3 times after Hioki's Stage 1 defeat; another contestant said it after their own defeat. How do you spell this, and what does it mean exactly?

Thanks!

[tns8597]

I can answer number 3 as I know minimal Japanese. It’s spelt maji-kayo.

It basically means ‘seriously?’ or ‘are you kidding me?’

That’s often why you hear it a lot when someone fails suddenly or early.

[ChiBiJKT48]

This is from what I know, obviously, so maybe it wasn't correct answers.

1. It was Nagano's request. He feel that he would be more confident if someone slap him in the back, like if when someone pat you in the back. The earliest I remember is SASUKE 12, which it was actually done by Yamada. In SASUKE 13 onwards, it become a tradition that was done by Takeda *since Yamada didn't appear in SASUKE 13*.

2. Yeah, from what I see, Shah! means Ha!, just an expression. A YouTuber made a compilation of All Ryo Matachi's Shah!
up to SASUKE 32, which is quite hilarious.

3. It is basically "Are you serious?", it was used when someone fail unexpectedly.