Does anyone else find that tightening the fist too much makes the arms tense and thus produce a weaker punch?

I believe its because antagonist muscles engage, making it sort of like driving a car with the parking brake on.

Its pretty obvious that if you're too tense and stiff, you're going to move slower. Staying relaxed is key. Tense up, tightening the fist only at the end of your punch.

I can tense my fist and have a fully loose wrist/relaxed arm.

It's about learning what muscles to tense and what muscles NOT to tense.

So the answer is no - tightening your fist does NOT have to tense your whole arm. Learning this is part and parcel of learning our basic techniques.

(I can video this for you if you want Vietpanda.)

The muscles involved in making a tight fist are found in the forearm. The beauty of this is that you can make a tight fist and have a completely relaxed elbow and shoulder which allows for a fast punch.

Most people tense every muscle in the forearm, where you don't have to in order to have a sufficiently tight fist.

Hence I can do an uraken (back fist) with a loose wrist but a tight fist. As I said, this is a basic.

Try keeping the pinky and ring finger tight and the other two fingers closed but relaxed. Tense the relaxed fingers just prior to contact. The same grip will come in handy when you do tonfa- to control tonfa in the spins using the grip on the handle and because it allows wrist movement for the spins. WHen you tighten up the first two fingers you can't roll the wrist.As already stated you can learn to relax the muslces that need to be relaxed.
The PP people will also tell you this grip helps strenghten against strikes to one of the meridians (heart?).

This is an ancient Okinawan secret so don't tell anyone.

Sorry. There are no tricks. You can keep the whole fist tight enough without having a stiff wrist. It's not that hard - come on, it's a basic technique for crying out loud!

Actually, you can not have a completely tight fist while having a relaxed wrist. It is anatomically impossible. It has to do with the fact that the finger flexors and extensors share a common origin with the wrist flexors and extensors. If the fingers are tight, the tendons cross the wrist and it is tight. That is why a person can not grip well when they have "tennis elbow".

The concept of the ureken and why you can have a tight fist at impact with bending wrist is due to tendon insufficiency. The tendons of the fingers are not long enough to allow both wrist flexion and finger flexion (or extension of both). If a person flexes the wrist, they can not make a fist (that is why wrist locks are good for disarming knives). However, when the wrst bends back into an ureken, the fingers "want" to bend and make a fist. It does not take a lot of extra effort to tighten them into a strong fist.

That is why I said "tight enough".

We're talking the right tension for a punch that does not cause your forearm to be so stiff as to preclude uraken.

It's a question of tightening the right muscles, not ALL the muscles in your forearm.

This is all a non-issue as far as I'm concerned.