How Many Ways Can You Cause a Stretch Shorten Cycle?

[Chas Tennis]

Believe there's a biological/ chemical process taking place inside/along the muscle.
(My sons taking physiology)

I don't think that there is anyway for a muscle to lengthen or stretch itself. It can shorten itself but I believe it needs external forces to get longer.

What you mention sounds like the active muscle process for shortening. The brain sends the muscle cell nerve signals, negative calcium held near the muscle cell (or maybe even in a special valve inside the muscle?) are released into the muscle. That causes Actin & Myosin to form 'crossbridge' links that cause the muscle to shorten. See Actin & Myosin video animations for the sarcomere.
Detailed explanation.

 

[Chas Tennis]

Is it momentum? Chas



Centrifugal force?


Or maybe, wind?

Describe the momentum with an example.

On the serve, the ESR muscles are used to get the forearm and racket moving up and back - at speed - into Trophy Position. That rotation speed or angular momentum might be considered as stretching the muscles that do ISR. If the ESR muscles have stopped producing forces but the upper arm and racket are still at speed that might considered a separate cause. Interesting.................??

Wind is a step too far I guess............??

#4 could possibly be a strong force for stretching muscles.

 

[Pete Player]

#4 - twist against a load of the racket momentum going back, while already pulling the handle forward. The muscle is already shortening, but does not move the throwing hand nor the racket forward before the momentum of the backward motion is countered by the forward motion releasing the stored energy.

Feel Tennis demonstrates the physics of groundies very well in their clip on swinging the racket back out to in and in to out goung for the shot. You are to start the forward hitting just a fraction before the direction change.

The harder you hit the earlier you start the forward move before the direction change. It is somewhat similar, what happens in a fuel engine with the sparkplugs and TDC. The fuel is ignited in the combustion chaimber before the TDC. The higher rev engine, the earlier you need to ignite. But if you go too early, the engine backfires.


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No more on pain meds - all contributed matter and anti-matter are still subject to disclaimer

 

[atp2015]

The stretch shorten cycle involves first lengthening and then stretching muscles and then using them like rubber bands to provide joint forces.

Keep in mind that muscles have no way to provide forces to lengthen themselves.

In tennis strokes, how many ways are there to stretch muscles for a stretch shorten cycle?

There are only three ways to stretch, anything else is just a synonym for one of the three. In fact, the third type is combination of first and the second acting at the same time.
(we are not really stretching just muscles, it's also the tendons we are after and add as much tendons as possble)
They are push, pull and twist (what's gravity? it's an example of pulling force). Pull is a force applied from the direction of the target, Push is a force applied from the opposite direction of the target. Twist involves applying both at the same time.
Core rotation is a twist - some muscles pull and others push. A twisting force is always angular because a liner push and pull at the same time is extremely short lived as one takes over the other as the effective force.

More importantly, the advanced skills utilize tendons as opposed to just muscles (popularly known as elastic energy). Muscles can be pulled or pushed voluntarily - but tendons are involuntary - we utilize muscles to stretch the tendons and release them like a spring. We want to keep tendons strong by stretching exercises. Since tendons are attached to the bones, use of tendons automatically means adding more bones to strike the ball.

 

[Chas Tennis]

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More importantly, the advanced skills utilize tendons as opposed to just muscles (popularly known as elastic energy). Muscles can be pulled or pushed voluntarily - but tendons are involuntary - we utilize muscles to stretch the tendons and release them like a spring. We want to keep tendons strong by stretching exercises. Since tendons are attached to the bones, use of tendons automatically means adding more bones to strike the ball.

Researchers did an experiment where a single rabbit sarcomere was isolated and experiments were done. Elastic force adequate to account for the muscles elastic forces appeared to be contained in the sarcomere itself, there were no additional tendon forces necessary. The source of that force in the sarcomere is Titin. Titin is a giant molecule that kinks or in some other way stores energy. My description may not be accurate so check it out. Search Titin. Titin is a very long molecule, but it is too narrow to see with visible microscopes. There are no visible light videos of Titin in action. It can be seen statically with electron microscopes in high vacuum.

Stretching tendons during a stretch shorten cycle as a means of storing significant energy seems incorrect but read some information on Titin and judge for yourself. If anyone finds an up to date reference book on Titin please let us know.

 

[Hmgraphite1]

So how much energy can be stored in bowing your bones to spring back like bow and arrow?

 

[atp2015]

Stretching tendons during a stretch shorten cycle as a means of storing significant energy seems incorrect but read some information on Titin and judge for yourself.

Even a minor inflammation of tendon saps strength to an extent, we can barely "lift fingers". How's it possible if tendons do not play a significant role? Unless there's a contradictory evidence, it's difficult to discount tendons.
From what I have read, the elastic energy is mostly from tendons. Anyone has links to articles?

 

[Pete Player]

Even a minor inflammation of tendon saps strength to an extent, we can barely "lift fingers". How's it possible if tendons do not play a significant role? Unless there's a contradictory evidence, it's difficult to discount tendons.
From what I have read, the elastic energy is mostly from tendons. Anyone has links to articles?

The question, is whether a tendon is elastic or not. Titin however is by structure a twisted protein molecule, which has elastic feature. Studies in mid to late 1990’s have suggested titin plays a role in muscles elastic response.

It might be, the pain information restrict brain to send contraction command to the muscle connected to that infamated tendon. Doesn’t have to be of elastic nature in that case. However also tendons may be a twisted structure. At least some of them are.


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[Chas Tennis]

Even a minor inflammation of tendon saps strength to an extent, we can barely "lift fingers". How's it possible if tendons do not play a significant role? Unless there's a contradictory evidence, it's difficult to discount tendons.
From what I have read, the elastic energy is mostly from tendons. Anyone has links to articles?

This publication involves the Titin measurements on the rabbit sarcomeres. I believe that somewhere in this article or another publication on rabbit sarcomere studies it said that the measured elastic properties of Titin in the sarcomeres could account for the observed overall elastic properties of muscles, no significant tendon elasticity required. Double check my information. This publication is 17 years old and there is a lot of more recent research. Herzog from Canada is a prominent researcher. Serious research reading. In general on such papers, read abstract, and discussion points made at the end, conclusions, etc as the details require background in the subject.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2290211/

Look at the other pulications on the side of the page. The PMC publications are free online. The PubMed publications may be about $30-40 each.

 

[Chas Tennis]

One example of an additional way to stretch muscles (not the abdominal muscles in this illustration)-
The method can be applied using other body parts.

Hint - The muscle involved will be stretched more. The lat.....

See posts by dominick1985 on Thoracic Extension.

https://tt.tennis-warehouse.com/index.php?threads/exercises-for-explosive-internal-shoulder-rotation-serve.574744/page-2#post-10708926

Back bending is likely to be too stressful for the backs of many/most players.

 

[Accountant]

Stretching tendons during a stretch shorten cycle as a means of storing significant energy seems incorrect but read some information on Titin and judge for yourself.

Here is a study from Stanford on Elastic Energy and The Kangaroo.

"...A kangaroo has extremely long tendons in its back legs that undergo drastic length changes when the kangaroo is hoping. Acting like springs, the tendons stretch under the weight of the kangaroo, and, while elongated, contain elastic energy. ..."

"...While the muscles in a kangaroos legs still work to help them hop, so much of the energy they use comes from the tendons. [1] Unlike muscles, tendons do not fatigue and they do not require oxygen to work. ..."

Elastic Energy and The Kangaroo

 

[Chas Tennis]

Here is a study from Stanford on Elastic Energy and The Kangaroo.

"...A kangaroo has extremely long tendons in its back legs that undergo drastic length changes when the kangaroo is hoping. Acting like springs, the tendons stretch under the weight of the kangaroo, and, while elongated, contain elastic energy. ..."

"...While the muscles in a kangaroos legs still work to help them hop, so much of the energy they use comes from the tendons. [1] Unlike muscles, tendons do not fatigue and they do not require oxygen to work. ..."

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This link is to the Stanford information.

Elastic Energy and The Kangaroo

This is course work. The biomechanical references are from 1978, 1998 and 1999. These references may not have considered the part played by Titin as is currently thought by some researchers. Herzog et al. . Titin is a giant stretch molecule in each sarcomere that is now believed to account for the elastic properties of muscles. In about 2004, an individual sarcomere of a rabbit leg muscle was isolated and the forces were measured without the tendon. More research has been done. Search Titin.

 

[Accountant]

When I click the link, it just keeps bouncing back to post #1 of this thread.

Elastic Energy and The Kangaroo

Fixed in original link or yous link below


Fixed Link