Saturday, December 25, 2010

Shenzhen Ping Pong: Li Jun at the Pacific club

In this increasingly homogenized world, minority styles are at a premium. For example, it's really difficult to find good choppers to loop against. Therefore this winter break, I was grateful for the opportunity to hit with Li Jun (李君) at the Pacific club while visiting Shenzhen.

She is a high-level chopper with Friendship 802 short pips with thin sponge on the red side (backhand) and inverted on the black side (forehand). Having resided in Belgium for a while, she speaks English (some Flemish as well) and understands my Cantonese. (I don't speak Mandarin unfortunately.) She was also ladies singles champion while in Belgium.

The so-called Pacific club, is officially called the 友傳乒乓城. It is conveniently located near the Mix City (万象城) shopping area in Luo Hu (罗湖). However, people know it as the Pacific club because of the name of the building in which it resides.

It has excellent air-conditioning (necessary for humid and hot summers in Southern China) and a range of court sizes. The cost (aka table fee) for one of the larger individually barriered courts ranges from around 40 to 55 RMB an hour: actual price depending on peak/off-peak demand. Of course, a large court is needed for the chopping game. (For comparison, an individually barriered court at the Shenzhen Century South China Table Tennis Club (深圳市世纪南华乒乓球俱乐部) that I've blogged about previously costs from 20 to 38 RMB per hour.)

In addition to the table fee, one must pay the coaching fee. In the case of Li Jun, she charges 100 RMB per hour. A reasonable practice session would range from 90 minutes to 2.5 hours. One needs about 20 minutes to warm up. And then looping 4 or 5 baskets of balls will take up the rest of the 2 hours. You can do the math.

First, let's warm up the forehand.

(Direct link to the video here.)

And then, the reverse penhold backhand.

(Direct link to the video here.)

As to be expected, you can probably see that my reverse penhold stroke has evolved a bit since my previous posts on the topic. (I may take the opportunity to blog about the technical changes involved next time.)

Finally, we are ready to loop for an hour or two. First, looping on the forehand diagonal.

(Direct link to the video here.)

Some background is appropriate at this point. I first learned to loop with short pips a long time ago. Despite switching to inverted at 1900 level, and progressing to a pretty solid 2100 rating years ago, the underpinnings of that loop with all its warts visible here (which currently hold me back) can be traced back to my first short pips experience.

In short, I'm attempting to dump and re-tool my forehand loop. (Yes, I want to get rid of that same loop stroke that got me over 2000.) However, years of inappropriate reinforcement has meant that change has been particularly hard to come by without impacting power and spin in a major way. In particular, the ingrained timing and over-large backswing that I have developed has been a barrier to progress. It's gonna take a lot of effort to re-program my muscle memory. Looping against chop is an excellent way to overwrite that muscle memory.

So on this visit, my plan was to play Li Jun every other day. This gives sufficient recovery time and also time to review the recorded video, and think about stroke changes. Since her chop is pretty high level, one must be able to loop a pretty strong ball even to put it on the table, and definitely a very strong ball if it's to challenge her chop. So there always pressure on the the looper. And under pressure, I tend to revert to old habits that die hard. Still, one must swim against the current sometimes... in order to spawn something better...

Thursday, December 9, 2010

Heart Rate Drift and Rate of Perceived Exertion

I'm what you might call a bit of a data junkie, but curiously enough I normally don't use a heart rate (HR) monitor. Let me explain.

On my road bike (or Computrainer stationary trainer), I have a powermeter that measures my output wattage (or workload). On the treadmill, I simply run at a fixed speed. For a given workout, I set the target wattage or treadmill speed manually and doggedly stick to it. Based on the rate of perceived exertion (RPE), I adjust the workout if necessary for next time. The HR falls wherever it may.

But that was before I acquired an iPod Nano 6G back in September (see blog post here). The 6th generation Nano not only records foot pod data but also can simultaneously record HR. Since then, I've been wearing my HR strap on treadmill workouts.

I ran twice earlier this week (Monday and Wednesday) on a treadmill in a very large, climate-controlled gym. There is a completely predictable and repeatable 20 beats-per-minute (bpm) rise in HR over the 50 min or so endurance run. See how remarkably similar the two profiles look below.

[Conditions: The treadmill speed was fixed to a lowly 7.0 mph (11.25 km/h) throughout each entire workout. (There is also a 5 min warm-up before the start that's not shown here.) The climate conditions in the gym were unchanging and perfect throughout. Also, I took a sip of water every 5 minutes like clockwork.]

So the HR drifts. Observable phenomenon confirmed. But what about perceived exertion?

Well, perceived exertion is actually also another pretty dodgy fish. Perhaps it's generally correlated with breathing rate in running but I'm not sure. But initially, I've noticed my RPE is relatively high during the first 10 minutes (despite the 5 min warm-up). I don't feel efficient. But I'm not breathing hard. After that, the RPE actually drops despite the HR steadily drifting upwards. I feel I am in the groove, so to speak. Nearer the end of the workout, I've noticed when my HR hits 168 bpm or so, I start to feel the RPE go up again. However, in neither workout did I exercise to exhaustion, or have to reduce the treadmill speed to accommodate fatigue.

So what can I conclude? If I go by RPE, I'd be adjusting the treadmill speed down, then back up and back down again. If I go by HR, I'd be steadily reducing treadmill speed as the workout proceeds. In the end, I think all of this is really just data for data's sake. There's a lot to say for just ignoring these indicators, beloved of coaches and exercise physiologists, i.e. leave those two up and down buttons alone, and just doing the damn workout and burn your way through those 700 kcal.

Tuesday, December 7, 2010

Shenzhen Ping Pong: the penhold grip

In table tennis, the penhold (or spoon) grip is the less common of the two major ways in which to grip the paddle. The self-descriptive shakehands grip is dominant in modern play. Shakehands offers particular advantages for two-winged attack that the traditionally one-sided penhold grip lacks, requiring instead excellent footwork to compensate.

However, in the last couple of decades, innovation in the form of the reverse (side) backhand has allowed modern penhold to compete with the backhand loop of the shakehands grip. In previous relevant entries in this blog, I have documented my attempts to acquire that reverse penhold backhand.

I (un)lucked into the penhold grip by accident. Many decades ago, someone with good intentions gifted me a Chinese-made, one-sided Double Happiness penhold paddle of the kind sold in department stores. It had short pips-out rubber on one side and merely painted wood on the other. Because of a grip size difference, blades for penhold and shakehands also typically have different handles: in particular, penhold handles are too short to hold comfortably with the shakehands grip. As they say, the rest is history: I'm stuck with penhold.

An interesting fact about the human wrist joint is that it has a remarkably limited range of motion. The wrist is really only capable of a limited amount of natural rotation (relatively unstressed) about the cylindrical axis. You can rotate the hand relatively far clockwise but not very far at all anticlockwise (without co-opting the elbow). The hinge at the base of the palm allows the hand to tilt (or "cock") forwards or backhands in addition to the rotation. Furthermore, it's abundantly clear that there is considerable variation in the degree of flexibility exhibited by different players. Small changes in how one grips the paddle can mean large differences in available paddle angle. And differences at the wrist can require (undesirable) larger compensatory differences at the elbow and shoulder. A little sad perhaps, but I can safely report I made it from absolute beginner to 2100 level in the 1990s without really knowing how hold a penhold paddle properly.

Although improvements have been forthcoming, I still cannot state with certainty that I know how to hold the paddle correctly. Having said that, I believe the correct way is to grip the paddle between the thumb and the back three fingers. Obviously, the handle fits in the valley between the thumb and index finger (section 2). But aside from that, a range of subtle but significant adjustments seems possible. The index finger is free to close around the handle or relax and slide away from the center of blade, therefore widening the grip to achieve a more vertical paddle angle when the reverse backhand is deployed. Straightening the back fingers a bit (at least the middle finger) also seems to help with the reverse block/punch stroke. Rotation of the wrist clockwise about the cylindrical axis of the forearm is also critical to helping keep the reverse penhold open and aligned parallel to the table endline. (Otherwise, it seems the natural resting angle points perhaps 45 degrees too far to the right.) In terms of the forehand stroke, straightening the back fingers seems detrimental to a natural followthrough and therefore achievable power. (I find its effect can be felt as awkwardness at the elbow.) One must either fix on a compromise position or be able to execute subtle shifts in finger positioning on the fly. Experimentation is necessary, plus (as I mentioned earlier) some people have much greater wrist flexibility than others.

As for the paddle, the Chinese handle itself seems largely standardized between manufacturers. (The Japanese/Korean and twiddler penhold handles are another topic entirely.) I have made some measurements with calipers that seem to confirm relative standardization. Comfort and fatigue are especially critical issues for reverse backhand penholders who need to put rubber on both sides of the paddle. The resulting paddle is oftentimes nearly as heavy as shakehand paddles, despite having a shorter handle.

For example, here is the Chinese-made Sword blade I've been playing with since I resumed the game until very recently. I find this handle extremely comfortable with minimal customization. It weighs about 188g complete. Only change has been to smooth the sharp edges at the neck of the paddle on both sides. Of course, comfort is individual, given possible variation in hand size.

I recently switched to a Butterfly Amultart blade. This blade is heavier and much faster than the Sword. I weighed two samples at 94g and 90g, respectively. Incidentally or not, it seems to partner Tenergy 05 extremely well (as long as one has the skill level to handle the extra speed, somewhat debatable given my circa 2100 level of play). Outwardly, the unmodified handle is dimensionally extremely similar to the Sword but I found it "too big" and strangely uncomfortably.

After a few weeks of trying to get accustomed to the Amultart blade, I had to carefully modify the handle (over a period of several days) using a Dremel tool to "thin" the center section down to 25.4mm to comfortably accommodate the knuckle area (shown as section 1, top picture) and thumb. I also had to "scallop out" the underside of the handle (for section 2, top picture). Initially, I was puzzled by this. But experiments with an identical Butterfly handle with a thinner center section confirmed to me that the extra core thickness of the Amultart blade was responsible. We're talking just a few mm, but the differences in grip feel substantial and significant. (Incidentally, that other blade was a penhold Innerforce ZL Carbon, which is lighter and plays slower than Amultart, but seems to be another stellar offering from Butterfly.)

Modifications are shown in detail below (1: top/side, 2: top, 3: side, 4: underside).

Note: I have included a small cut out for the thumb on top of the blade.


There exist penhold blades with special handles designed to facilitate use of the reverse backhand. I am grateful to those who brought my attention to the Gushi (古氏) and Sanwei (三维) designs below.