Friday, February 24, 2012

run walk

I've been neglecting my running recently.

For a variety of reasons, I've come up with excuses not to run. Lack of sleep, tiredness, work etc. In fact, I haven't run for a whole month. Shame on me. I put on so much weight, I just had to hit the treadmill today.

It's not that I don't have reasons to run. In fact, I've had a new run toy since Christmas. See below.

This is Sony's brand-new XBA-BT75 wireless earphones. They weigh almost nothing, 20g on my scale, that's less than 1 ounce. And these were not available in most countries when I got them over Christmas. So I was pretty chuffed about that. Plus the matching black Sony TMR-BT8iP bluetooth adaptor since Apple's iPod Nano 6g does't have built-in bluetooth.

The reason why I wanted this was of course to have a purely wireless connection between my earphones and the Nano. See:

My Nano is attached to my waistband (as recommended by Apple to get maximum accelerometer accuracy). And as you can see, wireless. Nothing between the earphones and my Nano to get tangled up. (The left and right earphones are wired together though.)

The earphones are rechargeable despite being so small (3.7V built-in Lithium ion battery). Battery life is rated by Sony at 3.5 hours. The bluetooth adapter is a considerable power drain on the Nano though. After an hour, my Nano reports a bit less than half the battery life remaining. So it won't do for a full marathon (not that I'm in any shape to run one right now.) So I guess the Nano will be the limiting factor.

Okay, enough about gadgets and back to running. I needed to lose weight. That means run volume. Unfortunately, since I'm out of shape, I can't survive a long continuous workout. So what to do?

The solution is to adopt run coach Jeff Galloway's run-walk training system. (See his website here.)

He says the run-walk-run ratio should correspond to the training pace used. And he recommends 4 min/walk 35 seconds for 8 min mile pace, and 4 min run-1 min walk at 9 min mile pace. I decided to run one complete mile at 8.5 min mile pace and walk for 90 seconds. While walking, I can rehydrate and towel off. Then do another mile. Repeat a total of 7 times to get comfortably over the 10K distance for the entire workout. (Total completed was actually 11.2 km.)

Here's the graph as reported by my iPod Nano:

Although my run was pathetic, I burned a total of 950 kcal. And to lose weight and regain my running legs, that's the kind of volume I need to do. I'm going to run every other day now until I'm back in decent shape.

Tuesday, February 21, 2012

Noam Chomsky visit

A couple of weeks ago, Noam Chomsky, the active and famous intellectual - now over 80 years old, visited the campus. It generated a lot of excitement. Actually I suppose I should say "supremely active": after all, he has published over 100 books and is the most cited scholar in the world still alive.

He gave two free public lectures, a general lecture titled "Education for Whom and for What?", and a more specialized lecture on the topic of "What is Special About Language?"

This was evidently quite an event for Arizona. From outside my office window, I could see long lines of people all afternoon, hours prior to his 7pm general lecture. He filled Centennial Hall (capacity 2500) plus two additional overflow lecture halls.

Arizona Public Media, which runs the local PBS tv and KUAZ radio stations, taped the lectures. Here are the links:

I was fortunate enough to be able to chat with Noam on two occasions during this visit.

(Picture courtesy of Samantha Wray.)

Wednesday, February 15, 2012

Y&T S-27 table tennis robot

You go back, Jack,
do it again...
wheels turning
'round and 'round
You go back, Jack,
do it again...

I have a Y&T S-27 programmable table tennis robot.

It is a high-end robot made in China. In 2010/2011, it was considered state of the art. I bought it in Zhongshan (中山), China back in 2010 and had it shipped home.

I only take it out about once a year because I prefer to play with people. Human beings have more natural variation, which can be both a blessing (helps train adaption) and a curse (inconsistency). The other big problem with the robot is that it doesn't have arms: you cannot see it swing at the ball like a human being. A large part of anticipation is seeing how the opponent reacts to and contacts the ball. With the robot, the balls just shoot out almost without warning from a tube.

Last night, for the first time in over a year I used the robot to do a drill. (Usually, I'm fortunate enough to be able to find players to come out and hit with me.)

I programmed a drill asking the robot to send alternately one topspin ball slightly to the right of the centerline (position 7) and one to the forehand corner (position 10). One from each physical robot head. I asked it to send 40 balls and stop. (As the video belows shows it actually sent 41 balls.)

The way these robots work is having a spinning motorized roller shoot balls from a tube. The more sophisticated robots use two rollers. The spin and speed of the ball is determined by two (orange colored) spinning motorized rollers: one that brushes the top of the ball and one that brushes the bottom. You get topspin if the upper roller spins faster than the lower one, and underspin if the lower one is faster.

I set the top motor to speed 6, and the bottom to 1. This means the balls comes to me already loaded with topspin. The higher the speeds, the faster the balls.

The frequency of ball delivery was set at the 2nd slowest setting. This produced balls at the rate of 1 per 1.75 seconds. That gives me plenty of time to recover between balls, and perhaps approach the ball a bit more deliberately instead of frantically trying to keep up and reacting like a headless chicken. And as I get used to the drill and learn to anticipate the ball, cognitively I'll be less overwhelmed, and be able to work on improving my form. At least, that's the theory...

The control panel settings are shown in the picture below (left side for left head, right side for right head):

I'm currently trying to retool my forehand loop stroke. In the following video, I'm practicing my counterloop; that is, I return the incoming topspin ball with topspin. Fight fire with fire, so to speak. I'm only partially there. I'm trying to backswing less these days. This saves precious tenths of a second. And I'm think I'm finally succeeding in this aspect.

(There are other strokes possible. For example one could simply block the incoming topspin. Especially if one has less time. See my earlier post and video with Crystal Huang here.)

Also, having the robot send balls alternately to different positions helps me train my feet to respond properly. I have to move. And keep my balance. Loop. And then not have my loop stroke throw off my balance because I need to respond to the next ball. Multiple small hops are vastly preferable to a single larger step because this allows for fine-grained adjustment. You'll be surprised how many hops are possible in half a second.

Maintaining balance conflicts with how strong you can counterloop. The momentary stop for balance on the right leg, and the waist twist and weight transfer are crucial aspects of this part of the counterloop equation. Although my loop percentage rate is satisfactory, judging by the video clip, I could improve quite a bit on the quality of my loop.

Link: here

Moreover, my followthrough is not where I want it to be at the moment. This affects the amount of power delivered tremendously. It's way too much to the right, crossing the imaginary centerline of my body. Where the stroke finishes also affects recovery time. This is a stroke error. Instead I'd like it to finish with the paddle more out to the front. Technically, I also need to work on holding onto the extended stroke position momentarily at the end of the stroke. I automatically drop the paddle at the end of stroke which prevents proper transitioning. This is another error.

These are all good reasons why you want to resist the temptation of setting the machine to shoot as many balls per second as you can cope with. It makes good sense to debug the stroke fully before increasing the tempo.

In summary, the robot is not just useful when you can't find anyone to play with, it's also a good tool for reprogramming muscle memory. The problem of course is making sure the new program being written is a true fundamental improvement over the old. That's where video analysis is extremely useful.

Saturday, February 4, 2012

A lesson with Crystal Huang: two left feet

This is the third entry in my continuing series about learning table tennis technique with Crystal Huang, a professional table tennis coach. These video clips were taken at the LATTA last weekend. (Previous entries can be accessed here: #2 too many degrees of freedom and #1 structural reform.)

Have you ever had the experience of attending an aerobics class at the local gym but came away discouraged, feeling utterly unable to follow the moves? If you understand what I'm referring to, you might empathize with me. If not, I envy your natural talent.

The video here will demonstrate that I am a particularly embarrassing example of two left feet. Since footwork is paramount in table tennis, this is a very big developmental challenge: a potential showstopper. In fact, it will become apparent that I can't even figure out a simple two point five step move even when it is repeatedly demonstrated right in front of me. Thank goodness for computer software, only when I viewed it frame by frame did the proverbial lightbulb go off in my head.

The specific challenge here is to move in correctly when the ball is played short to the forehand. Generally speaking, we have about 1/3 of a second to respond appropriately. Proper footwork is essential to getting in close enough to execute a decent flip, smash or push stroke over the table. Possessing a good stroke is useless without the necessary accompanying footwork. Rather like being all ready to ski without an appropriate vehicle to get you up the slippery snow-covered roads to that mountain that looks so good in the distance. Not sure that's the best analogy but, in table tennis, speedy footwork is needed to deliver us in about 2/10ths of a second close to where the ball bounces while retaining good body balance. And proper balance is needed to support good stroke execution and facilitate recovery.

Because this is all about movement, let's go to the video directly. We begin with the following drill:

Here the instructor stands at the top right corner of the diagram. The ball is blocked randomly to my backhand and forehand. I'm having trouble getting close to the forehand ball, especially when it bounces short near the net.

I have taken the liberty of adding commentary and translation where appropriate so you can follow Crystal Huang's instructional style. (For those who prefer to skip forwards, minutes 8:19-9:26 is where I'm utilizing the footwork in point play.) Also, since the video is a bit long, you might want to click on the "I" icon and set the resolution to 360p for a faster download.

Link: here

As should be clear from the video, my clumsiness resulted from my lack of understanding of how to perform the step, stop, step sequence. That is because I didn't understand what was really happening in real time. For those as translationally challenged as me, let me offer the following frame-by-frame explication. Thank goodness for video editing software.








(A) is the starting position.

In (B), body weight is shifted to the right.

This unweighs the left foot, which allows it to move towards the right foot, as shown in (C).

You can then stand on the left foot in its new position, and unweigh the right foot. This is shown in (D).

Then it's just a matter of picking up the right foot and placing it in under the table. This is exhibited by the sequence (E) through (G).

Notice the racquet arm does not move until (F) and (G). In other words, you don't backswing first and move later.

At (G), the weight is transferred to the right foot. Next, we need to lean the upper body over for reach when the ball lands short or close to the net. The left foot may go back a bit to counterbalance the torso lean. The free arm is often also used for this purpose.

Finally, one more critical point that may not be immediately apparent to some ping pong students is the fundamental idea to always pause momentarily and re-balance first after moving before hitting the ball. In this case, this would be just after the lean over from (G). That slight pause for balance makes all the difference in the world in making the push or flip stroke crispy (my terminology), i.e. much more effective.

If you need it, here is the video version of the frame sequence:

Link: here

Wednesday, February 1, 2012

A lesson with Crystal Huang: too many degrees of freedom

This is my second blog entry in this series about learning table tennis technique with Crystal Huang. For the first entry and a description of the motivation and goals of the series, see here.

The human arm is said to have 7 degrees of freedom. At the shoulder, we have 3 of those 7 degrees: up/down (i.e. pitch), left/right (i.e. yaw) and the ability to rotate (aka roll). The wrist is independently capable of pitch, yaw and roll as well. That makes 6. Finally the elbow has a single degree of freedom (pitch). So if you like, there are 7 positional parameters to the system.

When you perform an arm stroke, the number of parameters in the system multiplies. For example, we now have acceleration of the various parts of arm to take into account. Then factor in timing, and the position of the torso, center of gravity and feet placement. Add to that subtleties of ball contact and feel, and adjustment for the speed and spin of the incoming ball and where you intend to place the return, and you can see how sometimes it's difficult it is to reproduce a stroke even when we have it demonstrated for us up close and live. Anyway, that's my excuse for being a poor learner.

In the following video, I'm trying to learn a new forehand push stroke. The idea is to be able to receive the underspin (or sidespin) ball with the forehand side of the racquet, control and send it to different positions on the table reliably. I already have a forehand push I've been using for years, it's just not a good one.

The day before the video was recorded last weekend, I had about 15 minutes of instruction on the new stroke. Unfortunately, I confess I didn't truly "grok" or properly understand how the stroke should be executed. Even having the correct stroke demonstrated to me didn't trigger how it should feel. I was still not executing it well.

As this video clip shows, Crystal (after shaking her head) ended up coming around to my side of the table and moving my arm for me. This reduces the number of degrees of freedom of the arm to zero. And only then did I really understand what the stroke should feel like.

The video also contains captioning that I've added of Crystal's instructions during the session. This might be of interest to other table tennis students.

The video clip ends with me using the new forehand push to return service to different parts of the table. And then playing out the point.

Link: here