Wednesday 21 January 2015

More Thoughts on SUP Technique – Part 2

First off, let me say thanks to everyone who read the last post and to those who provided feedback on it or asked questions.  I’m stoked that so many people found it interesting and hopefully helpful, but I am aware that there might be need for clarification on a few things.  As well, some of the comments I’ve received have made me go back to the program to see if there is any more data of interest that I can present.

I think everybody understood the main point – that there is no one correct technique.  There are fundamental principles that are universally accepted such as pulling your board by your paddle as opposed to your paddle through the water, using big muscles preferentially over smaller muscles, maintaining positive blade angle as long as possible, and using minimal effort to go as fast as possible.  A paddler’s technique is simply his or her interpretation of how to move to best achieve those principles.  Because we’re all different both in terms of our strength and fitness, and our anthropometric measurements, we’re all going to approach achieving those principles differently.  The result is that Connor Baxter paddles differently than Danny Ching who paddles differently than Dave Kalama.  What they all have in common is that they are fast.

When analyzing someone’s technique I honestly believe that most people tend to look too readily at how a paddler’s body moves rather than what their paddle is doing and how their board is responding.  Small differences between individuals in hand position, bending at the waist, leg movement, rotation etc. aren’t necessarily the first thing we should look at because they may be irrelevant.  The movement of the board is what is we’re concerned with.  We should look at that first and consider both how it appears to ride and how fast it is going.  We should also look at the effort the paddler is putting into making his or her board move.  Heart rate can be used as a reliable and easy way to measure that.

If a paddler is moving his or her board fast with little effort, then some unorthodox movement we’ve identified is most likely of little relevance.  It’s most likely just a little idiosyncrasy of that individual’s technique.  However it’s when the paddler has issues in how their board moves, or is working too hard for the speed they are going, that we need to start looking more closely at what their paddle is doing and how their body movement is affecting it.  Then we can help them make specific, intelligent changes to body movements to get the paddle to do what’s required to get the board to move faster, while at the same time allowing them to paddle with a better speed to effort ratio.

More on where to exit

So when someone asks me, even after reading my last post, where I think they should exit I can’t really answer that question unless I watch them paddle.  I can’t say whether they should exit with their paddle before their feet or with their paddle past their feet.  There is no rule.  I can only watch them, see what type of success they are having with what they are doing and then go from there.Before looking at the exit, I would encourage everyone to think more about how much they load their blade at the catch and build on that load through the pull until the point where their blade is vertical.  Remember this is the part of the stroke where you can accelerate your board the most.  Once the blade is vertical I’d suggest you begin to unload your blade as smoothly as possible without rushing it, but at the same time without delaying it.   Unloading the paddle should feel natural and in rhythm with the entire stroke.   While there is no question that a paddler should be thinking of exiting after passing through vertical with his or her blade, if the blade has been loaded effectively and is unloaded smoothly it is going to take time to exit.  During that time your blade is going to be approaching (and perhaps passing) your feet.  As we’ve seen, a paddler just needs to keep some pressure on the paddle and it will keep the board accelerating through to the exit. There is nothing to be afraid of here.  It’s not going to slow you down.  When you’ve unloaded your blade in a way that feels natural to you and moved your body to set up your exit, you’ll find the blade popping out of the water with little effort.  You’ll know when to exit because it will feel right.  The exit almost happens by itself.

To exit earlier you’ll have to unload the paddle more quickly which, while possible, often leads to a paddler placing less load on the blade in the first place.  This may not be what you want to do; as it will very likely lessen the acceleration you are able to get in the first half of the stroke.  You’ve got to experiment and play around to find the optimal load and optimal exit.  You’ll recall in the last post I mentioned a trade-off.  There is a definite relationship between the two.  I just don’t think you should be paranoid of pulling past your feet every time you stand on your board.  It isn’t that critical.

While I’ve just tried to answer the question “when should I exit?” by explaining the feeling of loading and unloading the paddle, those who are more mathematically inclined might better relate to the concept of diminishing returns.  Basically you need to exit when your blade reaches a spot in the stroke where you’ll gain more from starting a new stroke than finishing the stroke you are on.  At some point the acceleration you continue to get by leaving your blade in the water will decrease to a point where it just isn’t worth the effort.  It’s better to start a new stroke and get the maximum acceleration that next stroke can offer.  The caveat is you just need to understand that if you exit too early you are very likely going to end up having less weighted, less powerful strokes.   These won’t accelerate your board as much so you’ll have to take more strokes to go the same speed, hoping that your board will decelerate less between strokes because of that.  It’s like riding a bike in a lighter gear.   If this lighter load feels better on your muscles and makes you feel better on your board, and if you can aerobically handle the faster stroke rate, then that is probably right for you.  If you prefer pulling a little harder but less often then you should probably exit a little later.  You’ll find it harder on your muscles but probably easier on your lungs.  By experimenting with load and stroke rate you’ll get a good idea of which approach seems right for you pretty quickly.  Just remember whatever stroke you choose has to be sustainable for your entire race.

Acceleration and it’s relationship to board velocity

Someone who gave me feedback suggested that it would be good to see velocity data as well as acceleration.  I didn’t include it in the last post because the report we run to get a stroke profile doesn’t consider velocity.   I’m not sure why but it may have something to do with velocity being recorded by the GPS portion of the device as opposed to the accelerometer.   While the accelerometer part of the unit collects information at 200 Hz, the GPS portion gathers it much more slowly at 10 Hz.  Therefore there are a lot of points to plot for the acceleration curve and the curve shows all the small variances in acceleration and is essentially more accurate, while the velocity curve has far fewer points to plot and is therefore much smoother.   This means we cannot determine exact velocity for any given point on the curve but we can assume that the value we get from the curve is very close. I’m glad I looked for the velocity information provided in the data, as it is quite useful.  Additionally for good measure, and since the ride of the board was part of our original discussion on where to exit, I extracted some information on board pitch as well.

What you see below are two graphs of acceleration (black), velocity (red) and board pitch (blue); one for Jimmy Terrell and one for me.  For me there are six full strokes included and for Jimmy, since his stroke rate was marginally faster than mine, there are six and a small part of a seventh. 

 The acceleration curves should look familiar from the last blog post, though this time they are shown for one stroke at a time instead of a series of strokes that lay over top of each other.  Jimmy accelerates his board more quickly and we see he has greater peak acceleration, which again speaks to his technical strength as a sprinter.  My board actually accelerates for a longer period of time which is represented by a more stretched out curve.  Jimmy has a greater peak deceleration and his board is in deceleration for a slightly longer period of time.  What is new and interesting here is what we can see about the board velocity.

By definition, velocity should continue to increase as long as there is acceleration.   Therefore we should see peak velocity at the end of the period of acceleration or when the acceleration curve crosses the X-axis.   For both Jimmy and me you can see this is basically what we have.  Peak velocity for each of us is pretty close to the point where the acceleration is zero and deceleration is about to begin.  Where there is some variance from this point in a particular stroke it is due to the lack of sensitivity in the velocity readings mentioned above.  If the GPS had been able to gather velocity readings at a greater frequency the velocity curve would be more accurate and we would see peak velocity at the point where the board is just about to start decelerating.

For Jimmy, we see his velocity curves are steeper than mine meaning he reaches his peak velocity more quickly.  This should be no surprise based on what we have already noted about his acceleration.  Again, this suggests his technique is well suited to sprinting.  Jimmy’s velocity curve reaches its peak and then begins to drop fairly quickly; his velocity curve is steeper than mine on deceleration side of peak velocity as well.  In contrast, my curve is not as steep indicating I reach peak velocity more slowly.  What is interesting is that my curve is much more rounded at the top, to the point where for some strokes the top of the curve appears almost flat.  Since you achieve peak velocity when your board stops accelerating, but begin to lose speed the moment it starts to decelerate we know that flat tops to the velocity curve like we see here are by definition impossible unless the acceleration curve is flat along the X-axis.   So what we are in fact seeing is that my velocity is very close to peak for a considerable period of time.

Another interesting thing in the comparison of Jimmy’s and my velocity curves is that my curve doesn’t drop as low between peaks.  This is due to a) Jimmy having greater peak deceleration and b) a longer period of deceleration.  This causes Jimmy’s board to slow down more and for a longer period of time than mine resulting in the difference we see in our two curves.

Minimal velocity should, by definition, be at the point where deceleration stops and acceleration begins.  Again we can see this for both Jimmy and me within the margin of error due to the slower rate of collection of velocity data.  For both of our graphs the lowest velocity occurs just as the acceleration at the beginning of the stroke begins.

While we should have been able to infer this from the acceleration curves alone, the velocity curves show us the board moves fastest at the end of the stroke and slowest just as we are about to catch.  What is interesting is that, according to theory, the board is supposed to slow down if you pull past your feet.  However in this case the board of the paddler who pulled through further slowed down less.  We also see that the paddler who pulled it through further had considerably more time close to peak velocity than the paddler who exited earlier.   Maintaining near peak speed for longer and more speed between strokes are both significant.  Not only they do they mean you are going to complete a given race distance more quickly, maintaining more speed between strokes also means that you have less work to do to accelerate your board again at the beginning of the next stroke.  Provided you didn’t expend too much energy at the end of one stroke to keep your board running between strokes, you can enjoy notable energy savings over the course of a race.  Even if Jimmy and me are expending comparable amounts of energy each stroke, he is expending his relatively more at the front and me relatively more towards the back.  Again, this is an example of two different approaches to making the board move.

According to this data, for Jimmy to maintain more speed between strokes he would have to paddle with a higher stroke rate than he did for this test.  A faster recovery, which would allow him to get to the next stroke sooner, would mean there was less time for his board to slow down between strokes.Here is some quantitative data for each stroke.

Peak acceleration (g)
Peak deceleration (g)
Peak velocity
Minimum velocity (m/s)
Jimmy 1
- 0.19
Jimmy 2
- 0.24
Jimmy 3
- 0.28
Jimmy 4
- 0.24
Jimmy 5
- 0.30
Jimmy 6
- 0.23
Jimmy Ave.
- 0.25
Larry 1
- 0.15
Larry 2
- 0.19
Larry 3
- 0.15
Larry 4
- 0.17
Larry 5
- 0.18
Larry 6
- 0.13
Larry Ave.
- 0.16


In km/h the average velocities are: Jimmy peak 11.41, Jimmy minimum 8.35, Larry peak 12.13, Larry minimum 9.40.  Jimmy’s average velocity for the trial was 2.81 m/s or 10.12 km/h and Larry’s average was 3.06 m/s or 11.02 km/h.

I think it is safe to conclude that the fact that my board is not slowing down as much is because I have managed to widen my acceleration curve and have a smaller, shallower deceleration curve (meaning I accelerate longer and decelerate less).  I believe that has been achieved by pulling a little longer and not worrying if my blade has passed my feet.  And lets be clear, I am definitely applying something to the blade in these late stages of the stroke. Though most of the load has been removed from the paddle during the unloading phase, there is still enough on the paddle to keep the board accelerating.  It truthfully doesn’t’ take that much effort.  Had I stopped pulling, and was just letting the blade drift past my feet, I would not be producing acceleration and would likely be slowing the board down more because of paddle drag.   This is all interesting because the “it’s not good to pull past your feet” theory suggests that pulling at this stage of the stroke will slow your board down.

Though I was a little more successful than Jimmy at maintaining speed between strokes I can’t conclude from this exercise that exiting with the blade past your feet is better for maintaining speed between strokes that exiting before your feet.  I would need to include in this sample some paddlers who use that technique and collect data on them before being able to draw any conclusions one way or the other.   I would love to put the GPS/accelerometer on someone who exits really early and see what the data says.  There is as much possibility that they would maintain speed better as there is they would be worse.  I’m certain that they wouldn’t be able to load the paddle as much as if they pulled through more, and intuitively I believe that means they wouldn’t be able to accelerate as much.  Therefore I think it would take them a number of extra strokes to accelerate the board to top speed.  But if they didn’t slow down as much between strokes would they need to have as much acceleration in a given stroke to maintain a fast or perhaps even faster speed?  We won’t know until I can collect data from someone who paddles that way.  What we do know from data collected here is that there are different techniques that can make a board move fast.  I don’t’ think I can currently advocate that people should pull past their feet, just like I don’t think it is wise to advocate that people shouldn’t.  I think the best we can currently say is that people need to play around and see what works best for them.  My hope is that by helping people get a better understanding of how the board responds to different approaches to paddling they can make a more informed decision about which one to use.

Pitch – how the board rides

The pitch information from the graphs is interesting.  Pitch taken from this device is actually called “gyro pitch” and is measured in degrees per second.  Positive values mean the nose of the board is rising and negative values mean the nose is dropping.  I think the curves for both Jimmy and me are what we should expect to see.

In general, pitch increases as velocity increases, and you’ll notice on the graphs that pitch, in general, is increasing as the board accelerates.  Most paddlers will be familiar with the nose of their board rising as the speed of their board increases.  If you look at the front of your board as you accelerate on flat water you can usually notice the wave off the nose changing shape and moving further back on your board.  You may also notice it changing to white water and making a little “waterfall” noise.  This isn’t just because your board is pushing through the water more quickly.  It’s also because the pitch of the board is changing slightly.  You’ve probably also noticed when you draft behind another board that the lead board has a “rooster tail” like wave off the back of the board that increases in size during the stroke.  This change in size is largely due to the back of the board dropping slightly through the stroke which is also a case of the board changing pitch.

You’ll notice in the graphs that as the board starts to decelerate the pitch goes negative.  In other words as the board slows down the nose settles back into the water.  Again this is something that we’ve all experienced before.  Then once the board has finished settling it is neither falling nor rising so, as you would expect, the pitch curve is at zero on the Y-axis.  At this point the paddler is in the late stages of the recovery.  Pitch then goes negative again when the nose drops as you reach forward to set up your catch.  Whether you are in a racing canoe or a stand up board, as you reach forward to load your blade at the catch there is enough body weight transfer to cause the bow of the boat or nose of the board to settle again.  You shouldn’t stress about this.  It won’t slow you down unless you suddenly and violently dig your nose deep into the water (in canoe we call this bouncing the boat).  The pitch actually stays negative during the early stages of acceleration as you set and load the blade.  Then pitch increases again as our loaded blade works against the water and we accelerate our board past the paddle in the next stroke.

Graphically the pitch changes look quite extreme but I have tweaked the scale to make these changes more visible.  In reality pitch changes on a moving board should be easily discernable to the naked eye as fluid movement that seems to belong as part of the overall movement of body and board.  They should not be extreme.  The nose of the board should not come out of the water and the tail should not drop excessively.

One thing to note is that in this trial we were testing a Bark prototype board with very little volume in the tail.  Little volume in the tail means the board doesn’t support body movements as well and in particular doesn’t support a paddle being pulled past the feet as well.  The tail drops very easily and the nose rises very readily.  For this test I kept moving forward on the board until I felt my nose was staying down in the water more and responding in a similar fashion to my own Bark board.   I’m not sure that Jimmy made the same adjustments, as I can recall seeing the nose coming out of the water a lot more than normal as he was paddling.   It appears from the graphs that his pitch changes are larger than mine, which I don’t think they normally are.  It is possible that this affected his acceleration and velocity output as well, as when pitch changes are too great and a significant part of the board is out of the water at the nose, it should have a negative impact of the board’s performance.  After all, consider a case in which the first18 inches of a 14-foot board are out of the water.  It essentially becomes a 12’6” board that isn’t trimmed properly.

Hopefully this post has added some greater clarity to the “when should I exit” question.  Of course there is no simple answer.  You’ve got to experiment and figure out what works best for you.  Hopefully it has also provided some insight into velocity so that it isn’t confused with acceleration.  Finally, I’ve tried to add something extra by looking at pitch and trying to explain why your board moves the way it does.  I’d like to think that this discussion may help you better understand what your board and paddle are doing and help you better develop your own effective technique.

One of the sport scientists I am working with likes to say that the more questions we answer, the more questions we have.  There are more questions that spring to mind from looking at the data I’ve shared here.  How does pitch really affect speed?  How much pitch change is acceptable and when does it become detrimental?  How much does it slow your board now if you drag your paddle?  How much force is required to produce the acceleration we see here?  What is the load (in pounds or kilograms) in a typical SUP stroke?  What key fitness indicators might be useful in helping a paddler determine which approach to take in their technique?

One thing to consider is that this testing was done in the back bay of Newport Harbour.  I feel really confident in describing how a paddled craft moves in flat water.  What happens on open water like the Great Lakes or the ocean is different.  Is one approach to paddling better suited for flat water and one for the ocean, or is it still a case of what feels best for the individual?

 I’m really enjoying using this technology so far.  It’s certainly caused me to step back and question what I know about paddling.  It’s allowing me to help canoe and kayak paddlers by identifying the smallest details in their stroke and trying to optimize them.  When races are decided by 1/100s of a second these small details can make the difference between a spot on the podium or missing the final.  For stand up paddling it has been fun to use it to learn more about the stroke and really put the theories on how to paddle SUP to the test.  While I find the SUP stroke really does mirror the C1 stroke very closely, there is much more to learn, as there are many more variables, particularly when you consider the conditions we paddle in.   I would love to be able to use this technology to take a look at the strokes of some of the top paddlers, both so I can learn more about what makes a SUP board go and also to perhaps help them optimize techniques that already work extremely well for them.  Hopefully I can stick the unit on some of their boards during the Carolina Cup weekend.