BBBAKAMONO DA! DOITSU NO KAGAKU WA SEKAI ICHI!
On a serious note, that is an intresting concept author used in here, with muscle flexing, most of people who work out professionaly know about brain-muscle connection and how you need to consciously contract muscles when you work out to target them ofcouse here it's exagereted beyond real life level, but still not out of this world concept wich is nice =)
Also taking a vertical hammer fist from a 2m and 100+ kg dude with the only idea of "countering" it is dumb, if person knows you're up to counter it.
Thanks Hokuto no Gun for translation!