The Physics of Power: How Angular Momentum Shapes the Tennis Forehand

[jeffreycounts]

Let's discuss Chris Lewit's article, "The Physics of Power: How Angular Momentum Shapes the Tennis Forehand"

[jeffreycounts]

Sorry guys, I accidentally deleted this thread. Airforce1 had a comment about the article being biased towards the straight armed forehand, and that a bent arm can produce just as much power. If you watch Sinner, with his bent arm, for just a minute you can see how he obliterates the ball. So I would argue that you can get just as much angular momentem with the bent armed forehand, but some of the physics changes with the length of the lever. I'll leave it to Chris though.

[rstrecker]

Jeffrey’s comment brings to mind something I’ve wondered about within the bent v straight arm forehand discussion. I’m not a mechanical engineer but I wonder if there is an element missing in the analysis. Let’s grant the basic idea that, given a particular angular velocity, i.e., greater speed of rotation, there is a mechanical advantage to a longer lever because the tip speed will be higher. This is basic high school physics.

But, is it possible that players who use a bent arm can generate more angular velocity because it takes less effort to do this with a shorter lever? If you look at some great players with very bent arms on the FH, e.g., Sam Querry, Jack Sock, Nick Kyrios, Osaka when she was winning, Iga, Goran Ivanisevic, it always looks to me like they rotate unbelievably quickly and get very high racquet speeds. To look at a classic example of this in another sport, consider a classic figure skater’s spin. The spin typically starts with the arms fully outstretched horizontally and then as the skater brings the arms up over the head, thereby shortening the lever, the body rotates faster and faster.

This idea would suggest there might be a trade-off where a player with a bent arm can rotate the torso faster and generate equal tip speed to a player with a straight arm who is rotating a bit more slowly but getting the same speed through a longer lever.

Chris Lewitt, if you’re listening, we’d love to hear from you!

[stotty]

My question to Chris and other posters would be:

From a biomechanical standpoint, when executing a one-handed topspin backhand, which stance is more conducive to generating maximum racket head speed and power — a neutral stance or a closed stance?



Below is an excerpt from an email exchange I had with John Yandell back in October, 2020. It gives some insight into his feelings about Tennisplayer and its place in the tennis world. I find it inspiring.

My feeling is that Tennisplayer is like the New York Times or the Economist. You need to care, have curiosity and some intelligence to respond to it.

[jeffreycounts]

Jeffrey’s comment brings to mind something I’ve wondered about within the bent v straight arm forehand discussion. I’m not a mechanical engineer but I wonder if there is an element missing in the analysis. Let’s grant the basic idea that, given a particular angular velocity, i.e., greater speed of rotation, there is a mechanical advantage to a longer lever because the tip speed will be higher. This is basic high school physics.

But, is it possible that players who use a bent arm can generate more angular velocity because it takes less effort to do this with a shorter lever? If you look at some great players with very bent arms on the FH, e.g., Sam Querry, Jack Sock, Nick Kyrios, Osaka when she was winning, Iga, Goran Ivanisevic, it always looks to me like they rotate unbelievably quickly and get very high racquet speeds. To look at a classic example of this in another sport, consider a classic figure skater’s spin. The spin typically starts with the arms fully outstretched horizontally and then as the skater brings the arms up over the head, thereby shortening the lever, the body rotates faster and faster.

This idea would suggest there might be a trade-off where a player with a bent arm can rotate the torso faster and generate equal tip speed to a player with a straight arm who is rotating a bit more slowly but getting the same speed through a longer lever.

Chris Lewitt, if you’re listening, we’d love to hear from you!

I agree with all your thoughts on this rstrecker. I also think you can get more external shoulder rotation with the bent arm in addition to the faster torso rotation (the ice skater analogy you mentioned). And all the players you mentioned are great examples of all of this. I'll ping Chris and see if he can jump in.

[jimlosaltos]

I'll share this from Hugh Clarke {one of stroke's fav analysts) on Substack comparing the Sinner bent to Carlos straight (subscription)

"You can see the similarities in their unit turn: racquet head higher than the hand, wrist extended, which points the strings to the side fence, the left hand staying on for a great coil. One of the main differences is that Sinner plays with a bent-arm forehand that, when coupled with his fixed wrist position, means there is very little movement in the arm except for the shoulder. Djokovic is similar in this regard."

For what it's worth, both players hit 7 over 100 MPH forehands.

The aniGIF is too large to upload here even when I reduce the size and frame count but you've seen them both.

#

[airforce1]

Jeffrey’s comment brings to mind something I’ve wondered about within the bent v straight arm forehand discussion.

But, is it possible that players who use a bent arm can generate more angular velocity because it takes less effort to do this with a shorter lever?

Chris Lewitt, if you’re listening, we’d love to hear from you!

Not only is it possible, but we see this in the game every day in that, how they Lag the racket is partly a way to shorten the radius to aid in rotation.

[dimbleby69]

I'll share this from Hugh Clarke {one of stroke's fav analysts) on Substack comparing the Sinner bent to Carlos straight (subscription)

"You can see the similarities in their unit turn: racquet head higher than the hand, wrist extended, which points the strings to the side fence, the left hand staying on for a great coil. One of the main differences is that Sinner plays with a bent-arm forehand that, when coupled with his fixed wrist position, means there is very little movement in the arm except for the shoulder. Djokovic is similar in this regard."

Hi Jim,

thanks for the link to this. I might have overlooked it otherwise. I'm confused by this phrase: "wrist extended, which points the strings to the side fence". Given where it appears in the sentence, before mentioning the left hand staying on for the coil, it seems to suggest that they have their wrists extended long before the flip. I thought that the wrist only extends when the inertia of the racket creates the flip in the forward swing? That seems very clear on the gif of Alcaraz hitting a forehand on grass in the article.

Have I misunderstood something? Hugh Clarke, can you clarify??

regards
Rob

[stotty]

It’s All About The Player

Bent or straight—both can work perfectly well, and no biomechanist has ever claimed otherwise. But when it comes to efficiency, there are optimal ways to strike the ball, and a straight arm is slightly more efficient. On top of that there are genetic factors. Some players are more talented than others, some are gifted, and occasionally, very occasionally, you get a true genius come along —enter Roger Federer.

When we are talking long levers, well, some players have longer arms than others, some have stronger arms than others, some can swing a racket quicker and time the ball more sweetly than others. Genetics…you’re born with those.

There are so many factors the coach has zero control of or say in, the biggest of all being a player’s natural ability…the DNA…the coding. Good luck to coaches who think they can alter any of that lot.

[stotty]

It’s All About The Player

Bent or straight—both can work perfectly well, and no biomechanist has ever claimed otherwise. But when it comes to efficiency, there are optimal ways to strike the ball, and a straight arm is slightly more optimal and efficient. On top of that there are genetic factors. Some players are more talented than others, some are gifted, and occasionally, very occasionally, you get a true genius come along —enter Roger Federer.

When we are talking long levers, well, some players have longer arms than others, some have stronger arms than others, some can swing a racket quicker and time the ball more sweetly than others. Genetics…you’re born with those.

There are so many factors the coach has zero control of or say in, the biggest of all being a player’s natural ability…the DNA…the coding. Good luck to coaches who think they can alter any of that lot.

[jimlosaltos]

Hi Jim,

thanks for the link to this. I might have overlooked it otherwise. I'm confused by this phrase: "wrist extended, which points the strings to the side fence". Given where it appears in the sentence, before mentioning the left hand staying on for the coil, it seems to suggest that they have their wrists extended long before the flip. I thought that the wrist only extends when the inertia of the racket creates the flip in the forward swing? That seems very clear on the gif of Alcaraz hitting a forehand on grass in the article.

Have I misunderstood something? Hugh Clarke, can you clarify??

regards
Rob

You'd have to go to Hugh's substack page and possibly subscribe to ask him.

My humble interpretation wouldn't substitute

[jimlosaltos]

It’s All About The Player

Bent or straight—both can work perfectly well, and no biomechanist has ever claimed otherwise. But when it comes to efficiency, there are optimal ways to strike the ball, and a straight arm is slightly more efficient. On top of that there are genetic factors. Some players are more talented than others, some are gifted, and occasionally, very occasionally, you get a true genius come along —enter Roger Federer.

When we are talking long levers, well, some players have longer arms than others, some have stronger arms than others, some can swing a racket quicker and time the ball more sweetly than others. Genetics…you’re born with those.

There are so many factors the coach has zero control of or say in, the biggest of all being a player’s natural ability…the DNA…the coding. Good luck to coaches who think they can alter any of that lot.

Well put, Stotty.

Now, I'm imaging some tennis coach searching for a CRISPR, the gene editor approved for use on humans, such as fixing the sickle cell anemia gene

[doctorhl]

My question to Chris and other posters would be:

From a biomechanical standpoint, when executing a one-handed topspin backhand, which stance is more conducive to generating maximum racket head speed and power — a neutral stance or a closed stance?



Below is an excerpt from an email exchange I had with John Yandell back in October, 2020. It gives some insight into his feelings about Tennisplayer and its place in the tennis world. I find it inspiring.

Maybe this helps to visualize your question: In fast pitch softball most batters do not go past a neutral stance because of timing difficulty in making contact. In slow pitch softball many batters go well past a neutral stance to increase angular momentum and "swing for the fence". Their back almost faces the pitcher. My guess would be a closed stance generates more head speed.

[doctorhl]

In the wooden racket days, no one could conceive that anyone would have so much angular motion that players would some day spin off their front or rear foot and even leave the ground. Perhaps we might all someday witness a 360 degree followthrough!

[jimlosaltos]

In the wooden racket days, no one could conceive that anyone would have so much angular motion that players would some day spin off their front or rear foot and even leave the ground. Perhaps we might all someday witness a 360 degree followthrough!

You asked. Rinderkind vs Sinner if this uploads


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