well you're making sense now. i see what you're saying.
yes you can swing like that if you like.
however...
good forehands today and the certainly pros are rarely doing this. They are maintaining their hitting structure all the way through contact. Do you know what 'hitting structure' means? If not i can explain.
They are not using their biceps. They are using any combination of radial deviation, forearm pronation or internal shoulder rotation. This is very evident if you know what these terms mean. If they were 'pulling back' using their biceps you would see the arm/racquet/amount of elbow bend relationship change before or at contact. The upper arm / lower arm angle would change. I guess it happens in some instances but in the large majority of rally balls
the hitting structure stays the same. No bicep pulling. You can see bicep pulling in the student video. It pulls his arm into his chest.
Look at a slow mo of a pro. the racquet/arm relationship is the same until well after the hit.
Look at this djoko pic. If you used photoshop and moved the racquet behind his body it would look the same as it does in his takeback. He hasn't changed it. The ball is long gone here. No bend in the elbow. Everything is facing
forward. No bicep pulling. Compare that pic to oscar's student.
Also you can see the same thing in all of the other pics I posted. Look at the fed pic. his hitting structure has not changed since the first forward movement after takeback. Racquet / arm angles are EXACTLY the same. No bicep constricting.
Rafa takeback
Rafa at contact
Rafa well after contact and the ball is 20 feet away
Rafa's racquet / arm / elbow bend relationship is the same
all the way through and well after contact. It's the same at takeback, contact and follow-through. No pulling back. His hitting structure has remained unchanged.
You can see the same thing with bent arm fh's too so it's not related to straight arms only.
ISR, pronation and deviation is used to rotate that hitting structure. Not bicep pulling.
After they reach FULL EXTENSION then the elbow will bend
on it's own at the finish.
The evidence is clear in all these pics. No pulling back.