delaying the straightening of the arm

[blahness]

I noticed that a few players who use the straight arm FH actually do this while others don't. Basically some actually go to the backswing position with a bent arm - then the arm straightens during the forward stroke itself and then snaps back to bent during the ball contact. What is the advantage of doing this vs just straightening it directly during the backswing?

 

[hclnnkhg]

I noticed that a few players who use the straight arm FH actually do this while others don't. Basically some actually go to the backswing position with a bent arm - then the arm straightens during the forward stroke itself and then snaps back to bent during the ball contact. What is the advantage of doing this vs just straightening it directly during the backswing?

Try doing both yourself. My personal feeling is that if I only straighten my arm during the forward stroke, then my shoulder would move forward first while the arm lags behind my body, hence achieving a "bigger backswing" (arm relative to body).

 

[turbozed]

Not sure if this is exactly what you're referring to but, according this coach, it's just a faster backswing due to decreased rotational radius:

(Turn on subtitles)

 

[dingyibvs]

Not sure if this is exactly what you're referring to but, according this coach, it's just a faster backswing due to decreased rotational radius:

(Turn on subtitles)

Agreed, that's what I found as well.

 

[Tony's Table Tennis]

I noticed that a few players who use the straight arm FH actually do this while others don't. Basically some actually go to the backswing position with a bent arm - then the arm straightens during the forward stroke itself and then snaps back to bent during the ball contact. What is the advantage of doing this vs just straightening it directly during the backswing?

I have seen both as what you say.
I have also heard of newer techniques of smaller backswing
There are so much theory around this and I think each has its own merit.

To me, it is more important to have some backswing (not too much) and then forward stroke and most important is the snapping back to salute. This last bit was all I did when I visited another school last week and helped 2 players all of a sudden, having more high quality FH balls.
The player was like "finding the ball" to grip. I said, don't worry about it, when you see your contact point, just snap and salute very fast.

 

[zeio]

In addition to recovery, it probably has something to do with the "stretch shortening cycle". Muscle can exert more force when stretched eccentrically (sort of a subconscious self-protection mechanism). To take advantage of that, the stretching period (eccentric phase) must be kept short.

stretch shortening cycle | davidpotach.com

davidpotach.com

Phase II is the time between the eccentric and concentric phases and is termed the amortization—or transition—phase. This is the time from the end of the eccentric phase to the initiation of the concentric muscle action. There is a delay between the eccentric and concentric muscle actions. The nerves transmit signals to the muscle group. This phase of the SSC must be kept short. If the amortization phase lasts too long, the energy stored during the eccentric phase dissipates as heat, and the stretch reflex will not increase muscle activity during the concentric phase. Consider the long jumper mentioned previously. Once he or she has touched down and movement has stopped, the amortization phase has begun. As soon as movement begins, the amortization phase has ended.

Eccentric Exercise

Nonetheless, one of the first research observations with eccentric muscle actions was examined in 1882 by Fick, when he discovered that a contracting muscle under stretch could produce a greater force than a shortening muscle contraction (Lindstedt, LaStayo, and Reich, 2001). About fifty years later, A.V. Hill (who became a Nobel laureate) ascertained that the body had a lower energy demand when doing an eccentric muscle action as compared to a concentric muscle action (Lindstedt, LaStayo, and Reich). According to Lindstedt, LaStayo, and Reich, in 1953 Asmussen introduced eccentric exercise as “excentric”, with 'ex' meaning away from, and centric referring to center, thus giving the meaning of moving away from center. Lindstedt and colleagues further explain that when the weight exceeds the force developed by the muscle, as in an eccentric muscle action, it is referred to as 'negative work”, because the muscle is absorbing energy in this loaded motion.

 

[blahness]

Not sure if this is exactly what you're referring to but, according this coach, it's just a faster backswing due to decreased rotational radius:

(Turn on subtitles)

Not really, he appears to be talking about the distance of the elbow to the waist which I agree should be small. You can straighten your arm during the backswing or keep it bent and still have the elbow close to the waist. But in his demonstration he appears to keep it bent too...

 

[turbozed]

Not really, he appears to be talking about the distance of the elbow to the waist which I agree should be small. You can straighten your arm during the backswing or keep it bent and still have the elbow close to the waist. But in his demonstration he appears to keep it bent too...

It's a little bit easier to see in this clip below between #3 style (labeled for beginner-intermediate level) and #4 style (labeled for advanced level):

For #4, he seems to be pulling back his scapulae and twisting his body like he suggests in the first video, and his arm fully straightens before contact. Still pretty sure this doesn't answer your question but posting it here in case it helps, since your description reminded me of this coach's FH drive technique.

 

[blahness]

In addition to recovery, it probably has something to do with the "stretch shortening cycle". Muscle can exert more force when stretched eccentrically (sort of a subconscious self-protection mechanism). To take advantage of that, the stretching period (eccentric phase) must be kept short.

stretch shortening cycle | davidpotach.com

davidpotach.com

Eccentric Exercise

This is really interesting, I never thought of it this way but it does make a lot of sense! So delaying the straightening of the arm allows the eccentric energy from the straightening to boost the concentric movement ie the contraction of the arm according to this theory.

I might give it a go.

 

[Dr Evil]

This is really interesting, I never thought of it this way but it does make a lot of sense! So delaying the straightening of the arm allows the eccentric energy from the straightening to boost the concentric movement ie the contraction of the arm according to this theory.

I might give it a go

This is the most efficient way to generate power. The kinetic chain is forward hip turn (power from the ground) leading extension (preloading biceps, as well as anterior deltoid and pec major) leading flexion (forward whip).

 

[blahness]

This is the most efficient way to generate power. The kinetic chain is forward hip turn (power from the ground) leading extension (preloading biceps, as well as anterior deltoid and pec major) leading flexion (forward whip).

Yeah, I've been toying around with it a bit, it seems that going to the backswing position with the arm bent is better than having the arm straightened - it seems to make for a more powerful "snap to salute" at the end. I think zeio's explanation is probably what is happening - if there's less delay between the straightening and the contraction it allows the contraction to become even stronger. Otherwise the arm stays in a straightened position for too long and that "stored" energy is lost.

Kinda like the example of half squatting before a jump. It's more powerful if you go into that half squat just before you jump, rather than staying in the half squat for too long a period of time.

 

[brokenball]

It is easier to get a faster rotation if the inertia is lower. It requires less torque. Reducing the radius of rotation reduce the inertia and the torque to achieve the same angular velocity. The faster angular frequency is offset by the smaller radius so the paddle speed remains the same though.

 

[blahness]

It is easier to get a faster rotation if the inertia is lower. It requires less torque. Reducing the radius of rotation reduce the inertia and the torque to achieve the same angular velocity. The faster angular frequency is offset by the smaller radius so the paddle speed remains the same though.

That's completely not what this is referring to - both strokes are essentially the same straight arm stroke with the straightening and contraction of the arm (changing the angle between forearm and upper arm), just with different timing of the arm straightening.

So what is being discussed is the 2 options:

1) go to backswing position and straighten arm at the same time, then contract the arm during contact.

2) go to backswing while keeping arm bent. Start forward swing while straightening arm, then contract the arm during contact.

 

[turbozed]

This is really interesting, I never thought of it this way but it does make a lot of sense! So delaying the straightening of the arm allows the eccentric energy from the straightening to boost the concentric movement ie the contraction of the arm according to this theory.

I might give it a go.

I don't think that's the whole story either. Most of the power coming from the forehand drive is coming from the legs, hips, and transferred through to the upper body (as Dr. Evil described above). The arm muscles contribute little power on their own in comparison, and power efficiency of the whole kinetic chain is going to depend on no power leaking out (e.g., through poor bracing of the core, lats, etc.) prior to the energy concentrating in the arm.

If anything, the straightening of the arm at the point of impact may serve as a good cue to concentrate the power in a shorter period of time because the rotational axis is shortened and the motion is faster. This means less time for the power coming up from the legs, through the hips, and to the arm to leak out. In boxing or combat sports, we are taught to stay loose and snap out our punches (straightening the arm right at the moment of impact). This is also to concentrate the power in the kinetic chain in the shortest amount of time. I think any 'stretch reflex' of the arm muscle would only contribute in a minor way in comparison.

 

[turbozed]

It is easier to get a faster rotation if the inertia is lower. It requires less torque. Reducing the radius of rotation reduce the inertia and the torque to achieve the same angular velocity. The faster angular frequency is offset by the smaller radius so the paddle speed remains the same though.

You're 100% right about this. If power is generated at a singular moment in time from the very back of the backswing to bring the arm and paddle forward, then that's how it would play out.

However, in a properly executed FH stroke, the power is ideally applied after forward rotation has occured and as late as possible prior to contact with the ball such that peak acceleration occurs at the point of impact (instead of peak acceleration happening at the very back of the backswing). In this case, whether the wind up was bent arm or straight arm on the backswing shouldn't change the force applied to the ball too much (except maybe a miniscule amount of power inefficiency from longer rotational radius). So I think most of the benefit (if there is any) would be through better timing to get that peak acceleration at the point of contact.

 

[blahness]

I don't think that's the whole story either. Most of the power coming from the forehand drive is coming from the legs, hips, and transferred through to the upper body (as Dr. Evil described above). The arm muscles contribute little power on their own in comparison, and power efficiency of the whole kinetic chain is going to depend on no power leaking out (e.g., through poor bracing of the core, lats, etc.) prior to the energy concentrating in the arm.

If anything, the straightening of the arm at the point of impact may serve as a good cue to concentrate the power in a shorter period of time because the rotational axis is shortened and the motion is faster. This means less time for the power coming up from the legs, through the hips, and to the arm to leak out. In boxing or combat sports, we are taught to stay loose and snap out our punches (straightening the arm right at the moment of impact). This is also to concentrate the power in the kinetic chain in the shortest amount of time. I think any 'stretch reflex' of the arm muscle would only contribute in a minor way in comparison.

With both strokes the legs and hips are the major movers for sure. However the arm is also a major amplifier of that initial impulse and can be quite important imo...

I'm not sure the exact mechanics of it, but staying bent during the backswing and only straightening during the forward swing followed by contracting it during contact seems to give me a significant amount of extra acceleration somehow.... It does seem to "concentrate" the power better, by delaying this straightening of the arm.

Maybe what you're saying also contributes, that the shorter amount of delay between straightening and contraction actually helps to concentrate the power better and reduce power leaks.

 

[brokenball]

However, in a properly executed FH stroke, the power is ideally applied after forward rotation has occured and as late as possible prior to contact with the ball such that peak acceleration occurs at the point of impact (instead of peak acceleration happening at the very back of the backswing).

NO! if the paddle is still accelerating at impact then it hasn't reached the maximum speed and the maximum speed. Any acceleration acceleration after impact is wasted energy and will delay recovery as now you have to decelerate the paddle. You want to hit the ball with the maximum paddle speed and that occurs when the acceleration is zero. This is simple calculus. The trick is how thinly you hit the ball so you can make the optimal ratio of speed and spin.

In this case, whether the wind up was bent arm or straight arm on the backswing shouldn't change the force applied to the ball too much (except maybe a miniscule amount of power inefficiency from longer rotational radius). So I think most of the benefit (if there is any) would be through better timing to get that peak acceleration at the point of contact.

Myths.
Acceleration means nothing if the paddle isn't moving fast so it has momentum and energy.
In motion, the acceleration leads velocity and velocity leads position.

 

[turbozed]

NO! if the paddle is still accelerating at impact then it hasn't reached the maximum speed and the maximum speed. Any acceleration acceleration after impact is wasted energy and will delay recovery as now you have to decelerate the paddle. You want to hit the ball with the maximum paddle speed and that occurs when the acceleration is zero. This is simple calculus. The trick is how thinly you hit the ball so you can make the optimal ratio of speed and spin.


Myths.
Acceleration means nothing if the paddle isn't moving fast so it has momentum and energy.
In motion, the acceleration leads velocity and velocity leads position.

You're right. I meant to say that we want contact at peak velocity, not acceleration. However the point still stands that to get peak velocity then we want to accelerate the racket at some point in time well after the end of the backswing.

I think maximum velocity is the probably biggest factor but there are probably other considerations here. The ball isn't a massless object. The paddle is comprised of not just the blade but the rubber and sponge. Given a heavy enough ball and a sponge that isn't easily compressed, maximum acceleration right before the point of impact might be close enough to achieving optimal power where it might be a distinction without a practical difference.

At least with harder Chinese rubbers a lot of coaches I've watched advocate accelerating the blade right before the point of contact so as to compress the sponge and get the ball to bite into the rubber. Practically speaking, it's probably an easier cue than telling players to try to time maximum acceleration 0.5 seconds prior to contact or whatever the ideal point in time would be.

 

[latej]

I noticed that a few players who use the straight arm FH actually do this while others don't. Basically some actually go to the backswing position with a bent arm - then the arm straightens during the forward stroke itself and then snaps back to bent during the ball contact. What is the advantage of doing this vs just straightening it directly during the backswing?

For me this has two aspects, one I'd call "correctness" and the other one "efficiency".

I think you are interested in (and speaking only about) the "efficiency". Imo, even if the stroke is correct, there are differences between players and also differences in strokes of one player, depending on the position, time, intended power. So e.g. TB will have the arm more bent, and shorter snap, and ML will have slightly more straight arm, when the forward swing starts. But both are in a way perfect. And e.g. WCQ will start the forward swing with differently bent/straight arm depending on the type of stroke he's doing. So, I think, there is a range, and one can pick whatever one prefers, assuming the "correctness" is already there.

I tend to straighten the arm too early in the back-swing phase, which occassionaly makes me hit my right leg with my bat. That is no "correctness". Even though I don't straighten the arm completely, just straightening it too early in the back-swing is a problem. Video is a proof of it. Some people, not many, pointed that out to me. What I think is correct and what I want to improve, is to keep the elbow close to the body and to delay the straightening until I am rotated enough to the right with my body, so that hitting the leg is impossible (when straightening, because at least some straightening is my preference here). That makes the back-swing phase also more efficient, faster (but above it is about different efficiency, in forward phase).

 

[dingyibvs]

Not really, he appears to be talking about the distance of the elbow to the waist which I agree should be small. You can straighten your arm during the backswing or keep it bent and still have the elbow close to the waist. But in his demonstration he appears to keep it bent too...

There are two other issues with straightening during the backswing.

One, it's wasted energy. Your arm will naturally straighten as your backswing nears its end and your body movement/rotation starts to slow down so long as you keep your elbow relaxed, so there is no need to actively straighten it. Two, and I think it's the most important, if a ball comes unexpectedly fast or toward your body and you need to shorten your swing, you may not be able to do so if you're actively forcing your forearm in the opposite direction.

This leads to IMO the most important point, which is just to keep the elbow tucked to the side and keep the joint relaxed. Don't worry about straightening or bending the elbow, let gravity and your own body's momentum do the work.