But they still have value for me, for example the 2nd one. I may tend to have a slightly longer follow-through. It may indicate that I actually don't hit at the optimal moment of zero acceleration and max speed.
On that, one study from Taiwan (on FH and BH fast loop at maximum effort close to the table among 6 div A collegiate players in 2011) and a series of studies from China (on FH fast loop from mid-far distance among 11 national level players in 2016 and its BH counterpart in 2018, 2018, and 2019) have actually found that
the players do hit at nearly the maximum velocity upon contact AND accelerate through the contact, consistently.
How is that possible? It turns out that, instead of the resultant racket velocity (which is what many studies focus on), you have to look one step further at its 3 directional components - forward, upward, and lateral, as postulated by
another study from Poland in 2018. What actually happens is that
the players' stroke reaches the maximum velocity first in the forward direction moments before contact, and then accelerates through the contact in the upward direction. To be more precise, the curves of the forward, upward and lateral velocities are out of phase, reaching the peaks at different times. The prominent argument on reaction time is therefore irrelevant as the swing is moving in 3 directions simultaneously yet separately.
The findings in those studies support the notion of "
hit first and then brush", that is, wrap around the ball.
桌球正、反拍拉球動作之生物力學分析_黃信學
Fig. 4-1-1 Time of maximum resultant velocity of racket after contact
Legend
FH/BH: left/right bar
Left to right: topspin diagonal, topspin parallel, backspin diagonal, backspin parallel
https://i.imgur.com/Fr06PBv.png
Fig. 4-1-2 Time of maximum forward velocity of racket before contact
https://i.imgur.com/Vq99cfv.png
乒乓球正手中远台拉冲技术的生物力学特征分析_蒋津君
https://i.imgur.com/K2Pf6o1.png
Fig. 9 Resultant velocities and their 3 velocity components for shoulder, elbow, wrist, and racket markers for FH
Legend
a1/-2/-3: end of backswing
b1/-2/-3: impact
c1/-2/-3: end of follow-through
d1/-2/-3: recovery
Top part
Top right corner from top to bottom: racket, wrist, elbow, shoulder
Bottom part
Top right corner from top to bottom: racket-lateral, racket-forward, racket-upward
https://i.imgur.com/hE3JSjB.png
乒乓球反手中远台拉冲技术核心环节的运动学特征分析_蒋津君
Fig. 5 and 6 Resultant velocities and their 3 velocity components for shoulder, racket, elbow, and wrist markers for BH
Legend
Shoulder (blue), racket (red), elbow (green), and wrist (purple)
Racket X lateral (blue), racket Y forward (red), racket Z upward (green)
https://i.imgur.com/s3rnAhG.png