@Zeio, ould you elaborate a little bit more about the hit brushing and brush hitting? I don't quite understand the concept.
That one is a little lost in translation. In Chinese, the two terms commonly used are 先打後摩 and 先摩後打, where
摩 is commonly written as 磨, a variant form of the same word. Those two terms translate to English as "hit first, then brush" and "brush first, then hit", respectively. Due to space constraint, I shortened them to hit-and-brush and brush-and-hit in the sub.
Needless to say, people have been quick to point out that the lower limit of human reaction time and dwell time make either scenario outright impossible. However, the earliest instance of the concept that I could locate is aware of those issues, doesn't stress one over the other or specifies which one comes first, but merely promotes 打摩結合(combined hitting and brushing) and names this type of loop 打摩式弧圈, literally "hit-brush type loop".
And so, that topic has gone on to become one of the longest-standing debates of table tennis. AFAIK, discussion has been on and off on various Chinese forums for at least 20 years. The earliest internet thread,
"打摩式弧圈球技术及应用"(the technique and application of hit-brush type loop), was started by user 虎虎虎(tigertigertiger) in 5/2001 on Table Tennis Homeland, one of the oldest Chinese table tennis forums. The earliest instance in the Chinese magazine Table Tennis World dates back to the article
"正手拉球de发力方法"(method of force generation for the forehand loop) by
Zhang Xiaopeng in volume 4, 2002. See quotes below.
打摩式弧圈球技术及应用
随着乒乓球对抗力量和速度的日益加强,单纯以摩擦为主撞击为辅的弧圈球越来越为人所适应;如果打出的弧圈球没有一定的力量和速度,甚至会被对方反拉!
解决的办法并不是增加撞击减少摩擦(那是发力攻),而是增加撞击的同时保持原有弧圈的摩擦,这就是打摩式弧圈球。从中我们看到:传统弧圈以摩擦为主;发力攻以撞击为主;打摩式弧圈是既撞击又摩擦;所以说打摩式弧圈的手臂发力与前两者不同,比前两者更加复杂且难以掌握。只有在掌握了前两者以后,才有可能有手感去练习打摩式弧圈。
打摩式弧圈的发力顺序:发挥整个大臂前臂及肩背肌的力量去打击球,触球时再快收前臂发力摩擦,手腕较固定稍辅助发力摩擦,才有可能做到又打又摩。因为大臂力量较前臂大,而前臂速度较大臂快,才有可能在大臂撞击时用更快的前臂发力收缩摩擦,才能发挥撞击和摩擦的极限。单靠大臂去发力撞击和摩擦不行,单靠前臂也不行;靠大前臂同时发力撞摩也不行;后三者往往在撞击球后球已脱板,不可能再摩擦到球;所以一定要分工合作,打摩式弧圈才有可能。
正手拉球de发力方法
...
板形与击球部位
现代乒乓球的拉球更讲究“打摩”结合,所以拉球的板形不必过于前倾,这样容易造成摩擦过多,球的前进力不够。常用的板形是在拉球的起始阶段,板面保持与地面垂直即可。在击球的一瞬间,伴随着手腕内收,板面略有前倾,给球一定的摩擦。摩擦与撞击同时进行。在拉加转弧圈时,摩擦多一些;拉前冲弧圈,只要能保证有适当的弧线,使球过网上台,要增加撞击的比重,使球产生足够的向前冲力;当在第一点拉时,可增加撞击的比重;当在第二点拉时,要增加摩擦的比重;反拉时摩擦要多一些,自己发力拉时,撞击要多一些。
在击球部位上,拉下旋和一般旋转的上旋球,接触球的后中部向中上部摩擦;反拉强烈上旋球时,接触球中上部向上部摩擦;为了增加拉球的准确性,接触点可稍向左侧面一点,但千万不要侧面过多,形成拉侧旋球的情况。
TLDR:
先打後摩/Hit-brushing/hit-and-brush = hit first, then brush
先摩後打/Brush-hitting/brush-and-hit = brush first, then hit
打摩結合/Combined hitting and brushing = hit and brush simultaneously
打摩式弧圈/Hit-brush type loop = hit and brush simultaneously
So what really happens upon impact? Turns out the clues have been out there for at least 10 years.