Is there at least a universal consensus that maximal ESR occurs at frame 2, the so-called "cocking phase"?
Or can there be an even greater ESR after that point? I think this is what the OP is alluding to.
Four phases during high speed serve:
(I) backswing,
(II) maximum external shoulder rotation
(III) ball impact and
(IV) maximum internal shoulder rotation
You are thinking of maximum External Shoulder Rotation (MER) as depending only on the joint angle of ESR. When joint angles are measured, all other joint angles are held in place, prescribed, for the measurement. (Look up joint measurement videos and see how it is done.) In real motions, like the tennis serve, the other joints are changing, for example, with Thoracic Extension and Thoracic Flexion. I have had a thread about Thoracic Extension on the serve and how it changes the distance between the
origins of the lat on the back and its
insertion on the humerus. In other words, for Internal Shoulder Rotation (ISR), changing that distance affects how much the lat is stretched and thereby, how much ESR can be reached. Since that lat stretch is one thing that limits maximum External Shoulder Rotation - all bets are then off regarding "maximum" ESR. Remember that maximum ESR can only be actually measured under prescribed conditions of other body joints and parts.
That is a main point about the thread on
Thoracic Extension (TE) during the serve. TE would allow some more ESR and then Thoracic Flexion could produce ISR as the back straightens again -
as is observed.
To understand, first study "Two Joint Muscles" (TJM). This will show you how a second joint affects the range of motion of another joint. The lat has several
origins on the back so that it is a Multi-Joint-Muscle rather than just a Two Joint Muscle.
I have posted this for a few years and have never received one case of someone disagreeing with it, discussing it, or one question or even
any indication that anyone understands it. ?
Thoracic Extension may be very important for the serve? Time to acknowledge Thoracic Extension and the role it might be playing during the tennis serve. Speak up.
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WARNING - How your spine is used during the serve can risk injury. Many backs are not capable of much Thoracic Extension. ? http://www.racquetfit.com/articles/Screening/if_you_can%27t_extend_from_your_thoracic_spine_you%27re_squandering_power_and_inviting_injury The extension of the...
tt.tennis-warehouse.com
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Prescribed body & joint positions for isolating and measuring External Shoulder Rotation angle. Including Elbow bent 90 degrees, back straight (vs with Thoracic Extension)