Punching and Pushing: Is it better to tense up or stay relaxed at the moment impact?

[StrictlySP]

Hi OMGWTF,
You asked:

Do you clench your fist hard?

You turn the fist over?

Do you tense your arm chest and shoulder at impact (not before) or is this a no no?
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You aim at the back of the opponents head or you aim through* the heavy bag, (through the target) but at what point you you tense the fist? At the "surface"? Mid way "through" Or At the "end"?
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Also how long do you tense the fist for and how long do you continue to keep trying to drive through the target??

Hey buddy, you're getting too caught up in minutiae. So much so, that you'll be a victim of "paralysis by too much analysis." Whenever applicable, keep things as simple as possible. And this is an applicable case.

Generally speaking, it's best to keep as relaxed as possible (in the context of fighting - offensive and defensive execution). In regards to punching, staying as contextually relaxed as possible promotes speed and striking power (as your antagonistic muscles will not be impending performance).

As far as tensing the fist before or at moment of impact, don't worry about that. You'll "unconsciously" tense it at the moment of impact as contact with the target will elicit that naturally. The phenomena of tensing or not tensing your fist at the moment of impact actually works in reverse, consciously speaking. You have to consciously think about keeping your punching hand "relaxed" (i.e. a loose/untightened fist) at moment of impact if that is actually what you desire (which you shouldn't do). So, to reiterate, when it comes to tensing the punching fist at the moment of impact, that will come naturally without any conscious thought. So, don't think about it; let it go. There are more important things to concern yourself with on the road to mastering boxing.

On a tangential note, here's something to bear in mind when to comes to learning/mastering any facet of any skill - you go through four stages:
1) Unconscious incompetence > 2) Conscious incompetence > 3) Conscious competence > 4) Unconscious competence (which is what you should aspire to in attaining any skill, in this case, boxing).

I'm bringing this up because when a student is in the limbo realm between the "conscious incompetence" and "conscious competence" stages of learning, the "disease" of "paralysis by analysis" rears its ugly head to detrimental effect. So, be mindful of this in your training. Don't be sucked in by its charm...

Anyway, just let your punching fist do what it will naturally do on its own - tense itself at the moment of impact via reflexively-elicited tactile reaction. By the way, this "naturalness" also goes for the other related questions you asked (i.e. what to tense, how long to tense, drive through, etc). Just focus on the bigger picture (i.e. macro body mechanics and associated elements) and let the "micro" stuff flow naturally...

Take Care,
Lito