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Sunday, January 19, 2014 I 2:02 AM   
official bike trainers of:

You spin my wheel *the right way* round: Using the Spin Scan Analyzer

Spin scan bar graph in the Lake Placid real course video

In my maybe-not-so-humble opinion, I’ve had a successful 7 weeks of cycling, both on the CompuTrainer (CT) and on the Road.

I’ve steadily increased my average watts across all types of rides.

  • During my first three weeks with the CompuTrainer, from February 19-March 13, I averaged 159.9 watts on all of my rides combined.
  • During the past four weeks (March 14-April 9), that average has risen to 170.7 watts (2.9 watts/kilogram).
  • After the Boston Marathon (April 18th), I plan to do another FTP test to mark improvement in my power threshold. Stay posted for that number coming soon!

I’ve taken to the hills and soared.

  • Because John and I live in an elevation-challenged (i.e., FLAT) area of southern New Jersey, the CT is preparing me for hills in a way I couldn’t duplicate in last year’s training.
  • I’ve ridden the Lake Placid course, the Rev3Tri Quassy course, and countless other hilly courses (shout out to Ray for his recommendation on the Alien Crop Circle–you are twisted, my man…).

I’ve gutted through lung-splitting, mouth-frothing intervals. 

  • Based on the reports, I’ve steadily increased the wattage I’ve been able to maintain on 5-10 minute intervals from about 190 watts to over 200 watts. That increase came at the expense of quite a bit of suffering at the time. But looking at the numbers now, my once-a-week interval pain has produced measurable gain.

On the road, I’ve been able to make gains in speed, at lower heart rates (no power meter for the roads yet…). It seems that my desperation to become a better cyclist is starting to seem, well I guess, less desperate.

However, there is one aspect of cycling I’ve been ignoring somewhat: pedaling efficiency.

 Why ignoring, you may ask?

It’s not because I don’t think it’s important for my overall performance, as some research argues (see e.g., Coyle et al., 1991). In fact, I’m in agreement with the camp that concludes pedaling efficiency matters (see e.g., Burke & Pruitt, 1996) – especially when you have to run 26.2 miles after a grueling 112 bikes in the saddle. Based on what I’ve read and understand from experience about the transition from cycling to running, I believe strongly that pedaling efficiency does matter. Therefore, I’m going to sidestep the debate, and start with the assumption that pedaling efficiency matters.

Again you may ask, why have I been ignoring efficiency–especially given my belief that it makes a difference?

Well, I’ve been a bit mystified by it. The first time I rode the CompuTrainer, seven weeks ago, I was excited, but also a bit overwhelmed by all of the data it provided. To keep things simple, I zeroed in on those numbers that made the most immediate sense to me: heart rate, power, and cadence.

Since that time, I’ve learned how I can use those numbers to balance my effort for the various types of workouts I want to accomplish: tempo, interval endurance and so on. So, now it is time to move to the next level of analysis: the spin scan analyzer. (Cue the music, please…)

Using the Spin Scan Analyzer

What follows is a discussion of how we can use the CT spin scan analysis to make judgments about efficiency, technique, and even bike fit. For those of you who agree that technique matters, I hope that this information will prove useful to you–especially if, like me, you aren’t really sure what those spin scan numbers are all about. I’ll start with the basics of what the spin scan analysis describes, and discuss what these numbers tell us about our cycling. If I’ve managed to misunderstand some of these basics, I hope those of you with more knowledge and experience will help me fix that. (Your feedback is ALWAYS welcome here!)

The spin scan software offers a multifaceted assessment of the efficiency of your pedaling based on torque, the balance of power between left and right, and the balance of power between pushing and pulling on the pedal stroke. Luckily, the folks at CompuTrainer do not assume we are all physicists or engineers, so they give us three sets of numbers to make sense of what our bodies are doing in relation to the pedals. These numbers include: 1) your overall spin scan number for both legs and your overall spin scan for each leg, 2) your average torque angle for each leg, and 3) the power split between your left and right legs.

This information proves useful to confirm that a bike is properly fitted (or not), to identify imbalances in strength between legs, or to determine areas of weakness within the pedal stroke. If we can maximize efficiency and force, we can have not only better bike splits–but improved run splits as well.

Overall Spin Scan Number

The overall Spin scan number is a measure of your average torque throughout the pedal stroke, divided by the maximum torque possible  (times 100). The numbers range from 1 to 100.

But, who among us is doing maximal force for 360-degrees? If you scored a perfect “100,” you’d be a machine. Literally. So, I’ve had to give that one up. Not even Chris Lieto or Chrissie Wellington is boasting that type of efficiency on the bike. They might seem like machines, but it turns out they are simply super-human freaks of nature that work really, really hard in training :) .

For us mere mortals, an average Spin Scan number of between 70-80 would be good, with a number between 80-90 being very good. To break this range down further, if your numbers are between 70 and 80, that indicates that you are pushing down just a touch more than you are pulling back, and if you are between 80 and 90 you are starting to balance that differential out about as much as a human being might expect to be able to.

If your numbers are between 60 and 70, you are pushing much more than you are pulling, which is often referred to as “mashing” the pedals. While this will get you there, and will generate speed, it’s not efficient and it will definitely cause some problems for climbing, and on the run. Heavy legs are dead legs.

The bar graph below (supplied by http://www.wellsphere.com/triathlon-article/computrainer-preview-by-fred-doucette/546855) represents the torque of a rider’s 360-degree pedal stroke, broken down into 15 degree segments. The red bar to the left represents the force applied by the left leg at top dead center (TDC), the second red bar (180 degrees “later”) represents the force applied by the right leg at TDC.

This snapshot reveals an overall spin scan number of 67, a left spin scan of 62, and a right spin scan of 73. From this, we can surmise that the right leg is more efficient than the left. This difference may be the effect of several potential causes, such as differences in leg length, improper bike fit, or an imbalance in length strength. Visually, we’d want to see this bar graph as close to flat as possible (regardless of the height of the bars), again realizing that it won’t be perfectly flat because that would represent 100.

Both the numbers and the visual representation offer a clue for this rider that something is amiss in the pedal stroke. The lower areas in the bar graph identify which areas of the stroke require additional work by the rider, which may help him/her identify appropriate strength training. For example, it seems that the TDC of the left leg is weaker than that of the right, which implies the rider needs to work on the top of the left down stroke. Said differently, the weakness at the top of the stroke seems to be more pronounced that the weakness at the bottom of the stroke.

After seven weeks, my numbers have improved. From February 19-March 13, my average overall Spin Scan number was a 77.1; since March 14th, that number has risen to 79.0.

However, the numbers reveal an imbalance between my left and my right leg, with my left leg improving from 79.2 to 81.3, and my right leg improving from 74.9 to 76.8. I haven’t had a proper bike fit in over a year, so the first thing I need to do at this point is make an appointment for a bike fitting. While I’m happy that the numbers are improving, I’m not pleased that there is such a large discrepancy between my right and left legs. It is possible, that due to a curve in my spine, I may have a leg length imbalance that is causing this discrepancy.

The Power Split

In addition to the overall spin scan analysis, the image above also demonstrates the power split between the left leg and the right leg, which is illustrated by 55% and 45%, respectively in the image above. This means that the left leg is working harder than the right leg, which is also indicated by the higher peaks in the bar graph. Again, this may be due to imbalances in strength or leg lengths, or an improper bike fit.

When using the CompuTrainer, the manual and the Performance Improvement Guarantee program, created by Simon Ward, encourages riders to focus on keeping that power split as close to 50/50 as possible. In my case, I’ve gone from a left/right split of 48.7%/50.6% to 50.1%/49.9%. I will take the most recent numbers as the closest I can get to 50/50 without being a machine.

In the past two weeks, especially, I’ve paid close attention to the power split, working to ensure that my left and right legs share equally the burden of the work.

The Average Torque Angle

The average torque angle (ATA) refers to the location in the pedal stroke where force is applied in relation to top dead center of the pedal stroke.  For example, because we aren’t machines, we are likely applying the least amount of force, and therefore generating the least amount of power, at both the bottom dead center (BDC) and the top dead center (TDC) of the pedal stroke.

Ideally, our power would peak somewhere around 90 degrees from TDC. Otherwise, we are missing the opportunity to apply maximum force when it counts the most. From what I’ve read, this number can go as high at 100 and still be considered “good”. The consensus seems to be that any ATA over 100 degrees is inefficient.

In addition to the torque bar graph, the software also includes a polar graph to help assess the pedal stroke (see below). The polar graph provides a visual representation of the circular pedal stroke, as seen by the white figure in the middle of the shot, and it provides better analysis of the ATA, which is represented by the red line cutting through the diameter of the blue circle. Below the circle, we see the Left ATA (96 degrees) and the Right ATA (100 degrees) clearly identified

Why does the ATA matter? Most articles and videos emphasize that issues with the ATA may signal a problem with bike fit more than any other potential cause. Several coaches and cycling centers have recommended making minor adjustments with bike fit (one at a time), and then testing their effect on the ATA. If you’ve got the money, a professional bike fitting is likely your best (and quickest) bet.

My ATA has not changed too much, but it has gone from a Left ATA of 96.1 to 95.9, and a Right ATA of 98.2 to 97.9. Again, the differences in my left and right leg speaks to a potential problem with bike fit.

In addition to providing ATA information, the polar graph offers a useful way to envision the effectiveness of your pedal stroke. See how the image in the center looks like a figure eight, with the left side smaller than the right? The figure eight pattern quickly tells you that your pedal stroke is not efficient. The fact that the left side is smaller than the right quickly tells you there is a power imbalance between the right and left leg. A scan of the numbers at the bottom of the screen confirms this. An average spin scan (in green) of 61, with the right leg at 60 and the left leg at 63. (To clarify: the purple numbers are your spin scan numbers at that moment, not on average.) The averages tell us the cyclist is mashing on the down stroke.

Consider the difference in the image below.

While this figure still has a bit of a dip in the middle, we can see that it is much less like a figure eight, and there is an even split between the left and the right. The numbers confirm this, with an average overall spin scan of 76, a left SS of 77 and a right SS of 74. The power split between the left and the right is 50/50.

When I ride, I like to switch back and forth between the bar graph and the polar graph (by hitting F2 on the handlebar controller). I originally preferred the bar graph, but now that I understand how to read the polar graph, I think it provides more information that is immediately valuable to me – especially during intervals when the oxygen flow is diminished due to my anaerobic state.

The one downside to all of this is that if you are using the Coaching Software in the erg mode, you won’t be able to obtain any spin scan information. My solution? Do all of my rides using the 3d software or the real course video.

Using the numbers to make improvements

If the numbers are telling you that you could be more efficient (can’t we all?), then there are several steps to take.

First, make sure you have a proper bike fit.

Second, drill baby drill.

There are several types of drills I like to do that help me work on my pedal stroke, including single leg drills, power split drills (e.g., 80%/20% and switch) and high cadence drills, such as spin-ups. Each of these drills works well during both the warm up and cool down phase of your workout.

While it is possible to do these drills on the road, I believe they are more effective and safe on the CompuTrainer (or regular trainer). The advantage of the CT is you can analyze the data from your drills to mark improvement as it happens. This ability to chart improvement is motivating–it gives purpose and direction to almost any workout.

Third, try high cadence rides.

 In addition to drills, I like to do rides (30-60 minutes) that maintain a cadence of 100+ revolutions per minute (rpm). I think those rides, more than anything else, have helped my pedal stroke. Once you get used to them, they also work really well as recovery rides. But be forewarned: if you’ve never done a high cadence ride, the first few times will be challenging – both for your cardiovascular system and your neuromuscular system. I did my first 100+ ride in January. At that time, I was having a hard time maintaining an average cadence of 85 rpm for my “regular” rides. Now, I typically average at least 90-95 rpm, and I feel comfortable in that range.

Fourth, pay attention to your numbers.

As you play with your pedal stroke, the numbers respond instanteously, providing valuable feedback about what the correct form feels like. What happens when you get in the drops? On the aero bars? On the brake horns? What is the effect of fatigue on your numbers?

Knowing your numbers helps you work on your weaknesses in training, so when race day comes you’ve limited your limiters.

References: (Have additional references? Please include them in the comments!)

Burke, E.R., and Pruitt, A.L. (1996). Body positioning for cycling. High-Tech Cycling. Human Kinetics: Champaign, IL.

Carmichael, C. (n.d.) Training: Pedaling technique and efficiency. Retrived online 4/10/2011 from http://www.roadcycling.com/training/pedalingtechnique.shtml

CompuTrainer 3D Software: Users Guide (2009).

Coyle , E.F., Feltner, M.E., Kautz, S.A., Hamilton, M.T., Montain, S.J., Baylor, A.M., Abraham, L.D., and Petrek, G.W. (1991). Physiological and biomechanical factors associated with elite endurance cycling performance. Medicine and Science in Sports and Exercise. 23:93-107.

Drake, S. (n.d.) “Do you think I should lower my aero bars? Dynamic Bike Fit with the CompuTrainer’s SpinScan Takes the Guesswork out of Positioning.” Retrieved online April 3, 2011 from http://www.computrainer.com/html/coaching_corner/dynbikefit-example.html.

Energy Fitness Labs. (n.d.) The value of testing on a computrainer. Retrieved online April 10, 2011 from http://www.energyfitnesscoaching.com/article.cfm?id=142

McKinnon, K. (n.d.) So what’s the big deal about a computrainer? Retrieved online April 8, 2011 from http://www.computrainer.com/rm_inc/Stories/KMc_2.htm

Mooney, L. (n.d.) The perfect pedal stroke: How to get the most energy from each crank revolution. Bicycling. http://www.bicycling.com/training-nutrition/training-fitness/perfect-pedal-stroke

RacerMate. (n.d.) SpinScan Pedal Stroke Analyzer Software. Retrieved online April 5, 2011 from http://www.racermateinc.com/spinscan.asp

Winter, H. (2008). How to improve your spin scan. Retrieved online April 2, 2011 from http://hanswinter.wordpress.com/2008/12/29/how-to-improve-your-spinscan/.


Videos: (if you have a favorite video you’d like to add to this list, please include it in the comments.)

Spin Scan overview: http://www.computrainer.com/multimedia/RochSS.wmv

Basic explanation of spin scan bar graph and the polar graph: http://www.youtube.com/watch?v=hREeBWJEWVs

Explanation of bar graph, ideal numbers: http://www.youtube.com/watch?v=c2kdtBYUmUc&feature=related

Spin Scan across courses, new software capabilities http://www.youtube.com/watch?v=QEa7SHNq0to&feature=related

Going from a figure eight to a circle on the polar graph http://www.youtube.com/watch?v=AplnLW39RQA&feature=related