Not a question, just a progress report. This is the first time during a regular practice I was able to hit forehand with (almost) straight arm many times in a row. Yes, I am massively ahead of schedule here, this particular push is not heavy, hip rotation is probably not there yet (I feel like I definitely can do much more). But I feel like something good had happened.

Maybe I'm playing devils advocate here, but looking back at LTT60 it seems making the correct pattern with the arm was identified as the key to spinny serving. Now with the explanation given in LTT84, as with all the other strokes, it is the hip/lower body that is responsible for fast racket head speed, which equals more spin. Aren't these two explanations somewhat contradictory ?

They are mutually reinforcing. Good technique is complex. Focusing on any one thing will not give you good technique. But when you understand some of the elements, you can use them to diagnose issues and resolve problems.

You can use more or less muscle groups to activate the whip pattern shown in LTT60 or any other table tennis stroke. The largest muscle groups are in the hips. Therefore, they can do the most heavy lifting on many strokes. Efficient transmission of any work done by the muscles needs a relaxed arm.

When teaching a student you can't focus on everything at the same time. Some people just pick up on things by subconsciously copying others. But learning is a physical activity and you still need to build the muscle groups and neural pathways to support table tennis strokes. It is why it takes people time to learn to loop efficiently even when they understand the theory. Same with serves. These things take many hours probably years to refine and master. Looking for "gotcha " contradictions is not going to make a practical contribution to the learning process.

Even back before this video, I have always talked about being able to activate the whip of your strokes with other parts of your body. The degree to which you can do so makes the whip more powerful. But you can also activate the whip with less. I do it all the time as do people who play arm only topspin. Over time though, good hip work can become almost invisible on short strokes or blocks or even some serves. That can make them deceptive.

Not a question, just a progress report. This is the first time during a regular practice I was able to hit forehand with (almost) straight arm many times in a row. Yes, I am massively ahead of schedule here, this particular push is not heavy, hip rotation is probably not there yet (I feel like I definitely can do much more). But I feel like something good had happened.

I do think that goodtechnique's question is legit though and I expected it from a member. How does one make an advanced pattern whilst driving momentum from the hip in order to minimize complex arm muscle contractions? Solve the riddle during training and you'll have an excellent serve

So then they are both an essential in developing a spinny serve ? The question arose because in my mind LTT60 and LTT84 seemed to be two different ways of achieving the same result.

You have to turn the hips into the serve anyway to have decent recovery for the 3rd ball. If you finish the serve still completely side-on your 3rd ball will not be pretty. I have tested this many times.