During my 2001 Okinawa trip I was fortunate enough to spend quite a lot of time learning under Yasuda Tetsunosuke Sensei of the Naha Jundokan.
Whilst practising Sanchin kata, Yasuda Sensei told me off for making a ‘sanchin face’. Just before my return to England he took me out for lunch and told me that the most important thing for me to remember after I left was this advice about sanchin.
I find it curious that whenever you mention to fellow karateka that you are a goju ryu practitioner, they always seem to pull this ‘sanchin face’ while joking around that goju has too much tension. This is a regular reaction even in Okinawa!
Something that I notice often comes up in conversation when speaking about sanchin is the fact that it causes high blood pressure and can lead to health problems.
I think what Yasuda Sensei was hinting at was that there should never be an over tension during sanchin. There is a big difference between making the muscles firm, and making the muscles tense. Too much tension to the point where your limbs are shaking, you struggle to breath, you start seeing spots in your field of vision, and you finish the kata feeling exhausted is the incorrect way to practise sanchin.
As with all of your karate, nothing should be forced. Movements need to be natural, and should never be harmful if practised correctly. When you finish your sanchin practice, you should feel refreshed and energised.
It is my opinion that the face pulling, over tension, and hard shime favoured in some schools of goju ryu is geared more towards impressing the public during demonstrations, rather than pure martial art.