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Identifying The Magnus Effect In Table Tennis

As we all wait for the elite professional table tennis scene to return in early May, in today’s post we will look at one of the more fundamental physical phenomena in table tennis that not all viewers are aware of: the Magnus Effect.

The Magnus Effect is a physical phenomenon that explains how the spin of a ball modifies its trajectory while the ball is in the air. Unlike other aspects of table tennis mechanics, the Magnus Effect is not the result of gravity and friction, forces that we are familiar with and experience every day, but the result of fluid dynamics. This makes it difficult to visualize and form an intuitive understanding of the Magnus Effect.

However, although it is difficult to create an intuition for the cause of the Magnus Effect, once you understand its results (which are extremely simple), then you can see how the Magnus Effect is present in several common table tennis contexts.

What is the Magnus Effect?

A very non-rigorous explanation of the Magnus Effect (courtesy of Wikipedia) is as follows. When a spinning ball moves through a fluid (such as air), the ball “pushes” the air in one direction, and as a result of Newton’s Third Law (every action has an equal and opposite reaction), the air pushes back on the ball in the opposite direction. The visualization below shows a ball with topspin traveling to the right, which kicks up the air behinds it. As a result, the air exerts a reactive downward force on the ball.

If this is difficult to form an intuition around, that is fine; from a table tennis perspective what matters is not the cause but the effect of the Magnus Effect. The most important takeaway is that the Magnus Effect means that the spin of the ball affects its trajectory while the ball is still in the air and before it even hits the table.

Visualization of the airflow that causes the Magnus Effect

What makes the Magnus Effect counterintuitive is that for topspin and underspin, the direction of the force is opposite of what we usually associate for each spin. When the ball bounces on the table or off the raquet, we typically associate a topspin ball with jumping upward and forward (e.g. for a kicker serve) and an underspin ball will jump downward and backward (e.g. Ma Lin’s famous ghost serve).

However, by contrast, the Magnus Effect exerts a downward force (and a smaller backward force when the ball is falling) on topspin balls and an upward force (and a smaller forward force when the ball is falling) on underspin balls. We can better visualize both the direction of the Magnus Effect and how strongly it can influence the ball’s trajectory in the below video, where a basketball falling downward with backspin floats very far forward. If you tilt your neck sideways while watching the video, then you can see how a ball with backspin traveling horizontally across a table will feel an upward force due to the Magnus Effect (of course, in a table tennis scenario, this force is still weaker than gravity, so the ball still falls down onto the table).

Identifying the Magnus Effect in Table Tennis

At its essence, the Magnus Effect may be slightly counterintuitive but it is extremely simple: topspin is dragged down when the ball is in the air, and underspin is lifted up when the ball is in the air. We look at its consequences in two common scenarios: the fast topspin rally and the counter against a spinny opening loop.

The Magnus Effect In Fast Topspin Rallies

One of the biggest results of the Magnus Effect is that it is more desirable to add topspin to loops regardless of the speed. Spin vs speed is often viewed as a tradeoff where one must lose one to gain the other, which can be the case when the amount of spin/speed generated is limited by the player’s physical abilities. However, in the certain in-game contexts, increasing topspin may actually enable more speed. Watch the following winner by Ding Ning below.

The radar on the net measures the speed of the winner to be a fast 70 km/hr, but notice how the ball actually does not bounce that deep on the table. It only bounces roughly at the halfway point between the edge and the net both on Ding’s game-winner and the shot immediately before that. This is because the ball is loaded with spin (watch the ball roll on the floor when the point ends), so a heavy Magnus force drags the ball down faster. Hence, Ding Ning could have hit even faster, and the ball would still have landed within the table.

In general, adding more topspin counterintuitively makes the ball land shallower due to the Magnus Effect. This gives players a wider margin of error to hit the ball hard and fast without having to worry about it going off the table. As long as the player brushes the ball sufficiently and adds enough spin, the player can hit as hard as he or she wants and the ball will still drop down onto the table because of the increased Magnus force.

Although it is usually desirable to land serves, pushes, and opening deep onto the table, in the fast rally the ball is so fast and the opponent has so little time to react that the shallow depth appears not to matter much anyway. Moreover, with the heavy amount of spin involved and high downward velocity due to the Magnus Effect, the ball gets a serious kick once it bounces off the table. Looking at the slow-motion replay you can see how much pressure Ding Ning applies to Mima Ito during that point. On the first block, the ball is already up to near her face-level (granted, Mima Ito is short and also bending down). On the second shot, Ito is a bit late, and the ball jumps over her paddle.

Leveraging the Magnus Effect Against Slow Spinny Loops

Many amateur players have had the experience where, even if an opening loop is slow, if it is spinny it can often be quite challenging to block because the spin causes the ball to bounce off the racquet so that it flies off the edge of the table. One solution is to close the racquet and essentially hit the ball downward in order to counter the heavy topspin..

Alternatively, a player can simply add his or her own topspin to the ball, so even if the ball bounces off the racquet at a higher angle than expected, the Magnus Effect will forgive minor errors and drag the ball down. In the clip below, Ma Long opens his angle and counters Fan Zhendong’s slow spinny opening with a heavy topspin counter in which his racquet goes almost straight up instead of down or even forward.

Bonus: Around-the-net Shots

The Magnus Effect carries the most in-game implication for top-spin balls and topspin is usually the heaviest spin in the match, but it also affects heavy underspin and sidespin balls. For underspin balls, the Magnus Effect gives heavy chops their floating effect. While the distances involved in table tennis are too small for us to see some of the extreme bends that we do in soccer/football on sidespin balls, the curve induced by the Magnus Effect can clearly be seen in some of the more ambitious around-the-net shots that Youtube stars like Adam Bobrow take.

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Unfortunately, ITTF has killed ITTV, meaning that past matches are no longer publicly available to watch. Hence, no analysis blog posts are scheduled for the immediate future. You can check out past analysis posts here.

Chinese National Team Shares Their Travel Preferences

We translate a recent group of quick interviews about travel that Table Tennis World did with various members of the Chinese National Team over the last several weeks regarding their travel preferences (sources: one, two, three).

What is the favorite place that you have competed in?

Ma Long: Suzhou

Xu Xin: Shanghai

Fan Zhendong: I have traveled to many places for competition, but the places that have left the biggest mark on me are my first singles World Championships in Paris and my first team World Championships in Tokyo.

Lin Gaoyuan: Japan and Korea

Liu Shiwen: Tokyo

Ding Ning: I don’t have a favorite

Chen Meng: Weihai

Sun Yingsha: I go to wherever there’s good food haha

Wang Manyu: My favorite foreign country is Morroco. My favorite domestic city is Shenzhen.

Zhu Yuling: Korea

Which country or city have you been to that you would recommend fans to travel to and why?

Ma Long: China, it has has everything

Xu Xin: Fiji. The weather is good, the sea is good, and it’s expensive (luxurious?).

Lin Gaoyuan: Japan, the grilled meat is delicious.

Liu Shiwen: United States. I feel like there are so many places to go. Although I’ve been there and planned a lot, I haven’t really been to the most fun places.

Chen Meng: Qingdao, my hometown. The scenery is beautiful and it’s warm in the winter and cool in the summer. There’s also delicious seafood and Tsingtao beer, which will be worth it for everyone.

Sun Yingsha: Everywhere is not bad. I don’t go out too much haha

Where is somewhere you would like to go at least once in your life?

Ma Long: Iceland

Xu Xin: My dream when I was young was to go to Australia, and now I have been there.

Lin Gaoyuan: Maldives

Liu Shiwen: Maldives

Chen Meng: In the sky in a hot air balloon hahaha

Sun Yingsha: Paris

Do you like to travel with a plan or do you do what your heart wants?

Ma Long: A mix of both

Xu Xin: I travel with friends

Fan Zhendong: When you travel, you must go wherever your heart wants

Lin Gaoyuan: When I go out I must travel with a plan.

Liu Shiwen: I travel with a plan.

Ding Ning: I actually prefer to plan the first part, but once I get there then I like the kind of people who just follow their heart.

Chen Meng: I travel with a plan.

Sun Yingsha: Do what my heart wants.

Wang Manyu: Do what my heart wants

Zhu Yuling: I travel with a plan

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Analyzing Jeon Jihee’s Evolving Service Strategy Against Mima Ito

As a medal contender at the Tokyo Olympics, Jeon Jihee has a chance to make Korean Olympic table tennis history this summer. The most recent Olympic singles medals for South Korea are Kim Kyung-ah’s bronze medal in the 2004 women’s singles event and Ryu Seungmin’s famous gold medal in the 2004 men’s singles event. No woman from South Korea has ever reached the finals in the singles event. Similarly, the last time South Korea won a medal in the women’s team event was in 2008, and South Korea has never reached the finals in the team event.

Jeon Jihee has a puncher’s chance at accomplishing all of these things, but there is one player who consistently stands in her way to Olympic glory: Mima Ito.

Jeon’s Path To Olympic Glory

The Path to a Singles Medal

In the women’s singles event, there are roughly three tiers of medal contenders. In the first tier are the two yet-to-be-named Chinese women, who will be heavy favorites regardless of their seedings (although both will likely be top three seeds). In the second tier is second seed Mima Ito, who is quite widely acknowledged as the single most dominant threat to Chinese supremacy in the women’s events. In the third tier are seeds four through eight, which in order of projected Olympic seeding are Cheng I-Ching, Feng Tianwei, Kasumi Ishikawa, Jeon Jihee, and Doo Hoi Kem.

Let us first make the somewhat reasonable assumption that nobody in the third tier is able to pull off what would be a historically unprecedented upset against either of the Chinese women (although a historic upset is always possible and Jeon has beaten Chen Meng before in T2). Jeon’s viable path to an Olympic singles medal without having to defeat a Chinese player is as follows.

As a top-eight seed, Jeon is guaranteed not to play anybody higher ranked than her until at least the quarter-finals. In order for her to have the best chance to medal, she has to hope that she can avoid the Chinese players in the quarter-finals by drawing either Ito or the fourth seed. If Jeon is able to upset both the fourth seed and Mima Ito in some order, then she wins at least a bronze medal.

While it is unclear how the Olympic seeding rules work out this year, there is a chance that the two Chinese players may end up on the same half of the draw, in which case if Jeon defeats the fourth seed and Ito, then she will reach the Olympic finals.

The Path to Team Glory

With Jeon’s presence and the rise of teenager Shin Yubin, who notched impressive wins over Miu Hirano and Miyuu Kihara at WTT Doha and steamrolled the domestic competition at the Korean Olympic trials, Team Korea looks to be at the very least a bronze-medal contender and arguably the bronze-medal favorite in Tokyo. However, Korea appears to have loftier expectations.

In a press conference on March 15 (English translation on TTD), Korean table tennis legends Ryu Seungmin and Kim Taeksoo said that they believe that Korea has a solid chance at upsetting Japan and taking the silver medal (Kim also believes that only Japan can reasonably challenge China) at the Olympics. This is a bold proclamation as Japan’s lowest ranked player, Hirano, is higher ranked than Korea’s highest ranked player, Jeon. However, Korea has pointed to recent encouraging signs in their favor, particularly Shin’s win over Hirano and Shin/Jeon’s doubles win over Hirano/Ishikawa at WTT Doha.

Korea is likely closely monitoring the progress of Choi Hyojoo and Shin Yubin before making any final lineup decisions. However, from their remarks, Ryu and Kim seem to be signaling that Jeon and Shin will be playing the doubles match and that Shin will be playing singles against Hirano or Ishikawa. 

If that is the case, then Choi will play a singles match against Ito, who Choi came close to beating at the 2019 World Team Cup, and Japan’s choice of Hirano or Ishikawa, and Jeon will play Ito in a critical singles match should the two countries meet in the semi-finals.

Given that Jeon’s finals aspirations in both the team event and singles event likely run through Mima Ito, should Jeon spend the next few months hyper-focused on Ito similar to the way that China appears to be?

What are Jeon Jihee’s chances of pulling off the wins that she needs?

Jeon appears to have reasonable chances of upsetting the fourth seed in the women’s singles event (who will likely be Cheng I-Ching, Feng Tianwei, or Kasumi Ishikawa). Since 2018, Jeon is 4-3 against Cheng, 2-3 against Feng, and has not played Ishikawa in international competition. As we saw in WTT Doha, there is also a sizable chance that the fourth seed is not even able to make it to the quarter-finals.

On the other hand, we also saw in WTT Doha that Mima Ito appears to arguably be heads and shoulders above the rest of the non-Chinese competition, including Jeon. Since 2018, Jeon is 0-4 against Ito, including two 4-1 losses since the pandemic. Jeon will almost certainly walk into Tokyo as an underdog against Ito.

Although Jeon has had an underwhelming history against Ito over the last couple of years, their last two matches have been closer than the 4-1 scores may indicate. Out of the eight games that Jeon has lost to Ito in the last several months, three have been heart-breaking deuces.

First, at the 2020 World Cup last November, Jeon was up 10-7 and then failed to convert on four game points in a row to lose 13-11. Then at WTT Doha in March, Jeon lost a deuce 17-15 after Ito got a critical net ball at 15-15 in the second game. In the fifth game, Jeon was again up 10-7 lead and lost six game points in a row, resulting in a 15-13 loss.

Given the closeness of some of these games, even marginal targeted adjustments against Ito may be enough for Jeon to tilt the game more in her favor and pull off the upset in Tokyo.

The Story of Jeon Jihee’s Service Strategy Against Mima Ito

Mima Ito’s Domination on the Serve Return

One adjustment to her game that Jeon has already made and may continue to make against Ito is in the service. Shown below are the last four game points that Jeon failed to convert in game five against Ito at WTT Doha as well as the only match point that Ito needed to win the match.

Over the course of five consecutive critical service returns, Ito manages to receive every serve with the short pips on her backhand and does whatever she wants to them to create an advantage for herself on the next shot. She lands three chiquitas of varying side spin, a fast straight backhand flick, and a strawberry flick.

Why is Ito able to so freely create whatever she wants when receiving the short ball? Part of the reason may be that she does not fully respect the threat of Jeon’s long fast serve to the backhand, which allows Ito to fully focus on being creative with the short receive. Can we quantify how concerned Ito is about the long serve to the backhand and by extension how little attention she can devote to the receive on the short forehand corner?

One rough proxy is the number of times she receives a long fast serve with her forehand. When Ito receives too many long fast serves to the backhand and feels like she is unable to create an advantage on them, she tends to step around and open using her forehand. If Ito has to plan to open her stance for a forehand loop and additionally move left if she’s stepping around, then in principle it should become more difficult for her to move into the table to the short forehand corner to receive a serve with the pips on her backhand.

In Ito’s 4-3 win against Hina Hayata at the All Japan National Championships in January, Ito attempted to receive 13 long serves with her forehand (note this number also includes Hayata’s long serves to Ito’s forehand). In her 4-2 win against Hayata at WTT Doha, that number was 16. In her 4-3 loss to Kasumi Ishikawa at the All Japan National Championships, that number was 5. What about in her 4-1 win over Jeon Jihee at the World Cup last November? Zero.

Jeon raised that number to three in Doha. Let us take a look at the adjustment she made to cause this change, and whether she should further adapt her service game specifically for Mima Ito like other top lefties appear to do.

How Other Left-Handed Stars Serve Against Mima Ito

Jeon may have already started to adapt her service pattern to be more in line with several other left-handed players who are strongly motivated to optimize their games against Ito: Hina Hayata, Kasumi Ishikawa, and Ding Ning. Hayata and Ishikawa should be deeply familiar with Ito since they compete with her for domestic as well as international titles. Ding Ning, along with the rest of China, is likely also hyper-focused on Ito as she is the single biggest threat to Chinese supremacy.

We show selected points in some of their matches against Ito in the past year. Note that these are all very important points in the match. For Hayata and Ishikawa, these are their last few serves in a seven-game thriller. For Ding, these are her last three serves in a 14-12 win during a pivotal third game.

Several things stand out. First, all three of them are willing to challenge Ito on the long serve, even if it means letting Ito step around for a forehand opening. Second, Ito doesn’t do anything too fancy against them when they do serve short. Third, when serving they all stand inside close to the middle of the table (as opposed to the more common position of standing behind the corner), which appears to give them the flexibility to execute serves short to the wide forehand or long to the wide backhand.

Hayata and Ding can go full games serving entirely behind the corner, even at 9-9, but they do serve from inside the table throughout the match, and it says something that when they need points the most, they opt to serve from inside the table. Moreover, while Hayata likes to serve from inside the table against everyone, Ding and Ishikawa are quite clearly serving more often from inside the table specifically because they are playing Ito.

To get a rough idea of how heavily Ishikawa changed her service game for Ito in the All Japan National Championships, consider the following numbers. In Ishikawa’s 4-3 win over Ito in the finals, Ishikawa served from inside the table 85 percent of the time. However, in her 4-2 win over Miyuu Kihara in the semi-finals, Ishikawa served from inside the table only 21 percent of the time.

In Jeon’s loss to Ito at the World Cup, Jeon didn’t serve from the inside the table even once. This is in line with her and Ding Ning’s typical service pattern: almost always serve from behind the corner and possibly break out a different serve from inside the table to introduce some surprises during critical points.

However, at least Ding and Ishikawa have both apparently decided that such a service pattern is sub-optimal against Mima Ito. Jeon seems to have arrived at a similar conclusion as she heavily integrated more serves from inside the table at WTT Doha.

How Jeon Jihee Changed Her Serves At WTT Doha

Jeon Jihee notably started serving from inside the table against Mima Ito at WTT Doha in the second halves of Games 2, 3, and 5 after never doing so in the World Cup (she did, however, serve at least once from the center of the table in her 3-1 loss to Ito at T2 in 2019).

We caught glimpses of the potential advantages of using this serve. In the clip below, we see Jeon take a pair of points at 9-9 in the third game off two fast long serves to the backhand. Ito can only give a standard backhand flick return that is not particularly fast due to the short pips, which Jeon can take advantage of.

However, this serve is not a silver bullet to cure all of Jeon’s woes against Ito. Due to a combination of Ito’s brilliance and Jeon’s possible lack of familiarity with her own serve, some of Ito’s returns against this serve seemed to really catch Jeon by surprise. Jeon also may have signaled more information than she would like with her service stance; she was far more likely to serve fast and long to the backhand when standing inside the table. She can remedy this by serving to the short forehand from inside the table more often.

Jeon also almost certainly feels more comfortable with her usual serve from behind the corner. While she can surely execute her serve from inside the table perfectly during training, can she do it repeatedly when the pressure is on?

As seen in the first video clip in this post, to close out the match Jeon reverted to her normal serve from behind the corner even though Ito was having her way with them. Was this a tactical decision or was it because Jeon lost confidence in her ability to execute the serve well? Jeon did serve a long fast serve to the backhand from inside the table at 12-11, but Ito seemed to easily take advantage of it since the serve was predictable and/or not executed well.

It remains to be seen whether Jeon further integrates this serve into her matches against Ito in the future. At Doha, she only used this serve in the second half of a game and only if the score was within two or three points. This is roughly on par with (although possibly slightly less than) how often Hayata and Ding use this serve against Ito. Does Jeon want to fully adapt Ishikawa’s strategy in All Japan and essentially make this her default serve?

How Much Does Jeon Jihee Want Mima Ito To Step Around?

Counting the number of times Mima Ito receives a long serve with the forehand is always an interesting exercise. As mentioned earlier, the upside of Ito stepping around is that it means she can devote less attention to the short forehand corner. The downside is that it allows her to open with an aggressive shot.

However, a step around forehand from Ito may not be as scary as it sounds. Sure, if Ito knows exactly where the ball is going and has time to prepare, she can pretty much score an immediate winner with a fast wide smash to either corner. However, when she is on the move, not completely in position, and hitting it from a wide angle on her backhand corner, it is extremely difficult to go hard straight down the line to the left-handed server’s backhand.

The points shown below are quite illustrative of the risks and rewards of Mima Ito stepping around for the forehand opening on the serve return.

In the first point, Ito is only able to make a soft and somewhat predictable cross-court shot to Jeon’s forehand, and Jeon lands the strong counter-loop. In the second point, Ishikawa is waiting for the forehand counter, but Ito manages to get in position and land a smash to her elbow for the instant kill. In the third point, Ito prepares to step around, but Ishikawa serves short to the forehand, so Ito can only push with the forehand. Ishikawa loses the point, but she gets a desirable serve return from Ito.

No set formula exists for how often the opponent should want Ito to step around and take the forehand serve return opening. Even Ito probably does not know the optimal number. Hayata, Ding, Ishikawa, and Jeon (listed in order of willingness to challenge Ito’s long opening attack) have all tried various service strategies with varying degrees of success.

So far Ding has had the most success against Ito, but that can also be heavily attributed to the fact that she is Ding Ning. Meanwhile, Jeon has so far been the most conservative with the worst results (granted there are many other factors that account for her results), and it remains to be seen whether she will further adapt her strategy going forward.

If you liked this post, please share it with your friends and follow Edges and Nets on Facebook , Instagram, and Twitter to stay updated.

Unfortunately, ITTF has killed ITTV, meaning that past matches are no longer publicly available to watch. Hence, no blog posts are scheduled for the immediate future. You can check out past analysis posts here.