This reminds me how Hayata started bringing a hygrometer to tournaments starting with WTTC 2023 and gave a scientifically sound argument. Because a table tennis ball is so light (very little mass and easily affected by other factors), heat and mass transfer could readily occur when traveling in humid air and potentially affect ball flight, with condensation forming on the ball if the surface is cooler than the dew point of the surrounding air.
Since table tennis ball is smooth unlike other racket sports, the point of separation from laminar flow (where a thin layer of air sticks to the surface of the ball) to turbulent flow (where that thin layer of air tears away and turns into eddies/vortices) tends to be very early, leaving a larger wake behind the ball, which in turn produces more drag. It would be nice to know how humid air/condensation affect the point of separation.
世界卓球2023ダーバン 高樹ミナのダーバン便り（6日目）
張本／早田が金メダルに王手！ 木原／長﨑は個人初メダルで「最高に幸せ」
https://www.butterfly.co.jp/takurepo/tournament/detail/022562.html
そんな姉御肌の早田は技術やメンタル以外の要素にもアンテナを張り、最近はなんと湿度の変化も戦略に取り入れているという。
今大会にも湿度計を持ち込んでいる彼女いわく、会場の湿度が上がると「ボールに水の粒子が付着するためボールが重くなる」「ボールの飛びが悪くなる」などの観点から、パートナーの張本が練習や試合でミスをして焦り始めたときに、湿度の影響もあると伝えているそうだ。
例えば、中国ペアとの準決勝はこんな具合だった。
「ボールが飛ばないときに強く打つと自分たちが崩れてしまう。林詩棟選手に強く打たれなければスムーズに試合ができていくと思うので、例えば私がツッツキを早いタイミングでやって、林詩棟選手がバックドライブでキュッてかけたボールが湿気で滑るので、そこをストップかチキータに持っていくとか」
確かに湿度はプレーに影響を及ぼす。だが、湿度計まで使って対策を図るとは。努力家で研究熱心な早田らしいエピソードである。
張本／早田は26日、2021ヒューストン大会決勝で敗れた孫穎莎／王楚欽（中国）とのリベンジマッチに挑む。日本勢6年ぶりの混合ダブルス金メダルまであと一歩だ。
Hayata, who has a big sister-like personality, is also aware of factors other than technique and mentality, and recently she has even incorporated changes in humidity into her strategy.
She brought a hygrometer to this tournament, and according to her, when the humidity in the venue increases, "water particles stick to the ball, making it heavier" and "the ball's flight becomes worse," she tells her partner Harimoto that humidity is also an influence when he makes mistakes in practice or matches and starts to panic.
For example, the semi-final against the Chinese pair went like this.
"If we hit the ball hard when it's not flying, we would collapse. If Lin Shidong doesn't hit it hard, I think the match will go smoothly, so for example, I do an off-the-bounce push, and Lin Shidong's solid backhand drive would slip because of the humidity, and from there I'll do a stop or take a chiquita."
It's true that humidity does affect play. But to use a hygrometer to take measures. It's a typical story of Hayata, a hard-working and research-oriented person.
On the 26th, Harimoto and Hayata will face Sun Yingsha and Wang Chuqin (China), who defeated them in the final of the 2021 Houston tournament, in a rematch. Japan is just one step away from winning the mixed doubles gold medal for the first time in six years.
早田ひなが持ち歩く湿度計 「研ぎ澄まされてきた」心技体と「智」
https://www.asahi.com/articles/ASR703TMRR7LUTQP01S.html
60%台なら気にしないが、70%に届くと考えを巡らせる。
「湿気で、ボールに水の粒子が付着して重くなる。飛びが悪くなる」
68%と70%で感覚が違う、という。
ラケットに球を当てる角度、強弱を変えて対応する日もあれば、戦略ごと変えてしまう場合もある。
例えば5月下旬、南アフリカ・ダーバンであった世界選手権。
カラッとした陽気で湿度の低い港町は、混合ダブルス準決勝の日、雨で蒸し蒸ししていた。
日本から持ち込んだ湿度計は70%台を示していた。
ペアを組む張本智和に声をかけた。
「ボールが飛ばない時に強く打つと自分たちが崩れてしまう」
「（相手の男子選手が）バックドライブをかけたボールは湿気で滑るから、そこをチキータ（攻撃的なバックハンドレシーブ）に持っていこう」
いつもと球の軌道が違うことに張本も戸惑っていたが、「湿気の影響だから」と繰り返し、落ち着かせた。
2人は中国ペアを3―1で破った。
湿度計を取り入れたきっかけは、世界選手権の1カ月前、マカオであった国際大会で中国の陳夢にボロ負けした試合だ。
世界ランキング1位で東京五輪金メダルの陳には一度も勝ったことがないものの、直近の国際大会では2試合続けてフルゲームの接戦ができていた。
それがこの日、どのゲームも大差をつけられ0―3で完敗した。
調子は悪くなかった。
使う道具も前回の対戦と同じ。
相手の戦略もそれほど変わらなかった。
それだけに、解せなかった。
気になったのが湿度だった…
If it's in the 60% range, I don't mind, but when it reaches 70%, I start to think.
"Due to the humidity, water particles adhere to the ball and it becomes heavy. It doesn't fly as well."
She says that 68% and 70% feel different.
Some days she responds by changing the angle and strength with which she hits the ball with the racket, and other days she changes her entire strategy.
For example, the World Championships were held in Durban, South Africa in late May.
The port town had a dry, sunny day with low humidity, but it was humid with rain on the day of the mixed doubles semi-finals.
The hygrometer she brought from Japan showed a reading of 70%.
She called out to her partner, Harimoto Tomokazu.
"If we hit the ball too hard when it doesn't fly, we'll collapse."
"The ball coming from (the male player) backhand drives will slip because of the humidity, so let's go with a chiquita (aggressive backhand receive)."
Harimoto was also confused by the ball's different trajectory from usual, but she calmed him down by repeatedly saying, "It's because of the humidity."
The two defeated the Chinese pair 3-1.
The reason they started using a hygrometer was a month before the World Championships, when they were thoroughly defeated by China's Chen Meng in an international tournament in Macau.
Although she had never beaten Chen, the world number one and Tokyo Olympic gold medalist, in the most recent international tournaments she had played two consecutive close 5-game matches.
But on this day, she was beaten by a large margin in every game and was completely defeated 0-3.
She wasn't in bad shape.
She was using the same equipment as in the previous match.
Her opponent's strategy hadn't changed much either.
That was all the more puzzling.
What I worried was the humidity...
