Monday, August 22, 2011

My Retül Bike Fit Experience

We're all pretty good at naming our favorite bike makers, and if lucky get to own and ride our dream bike. One aspect that many of us pay relatively little attention to is a proper optimal bike fit.

I have now owned my "delight on two wheels", a Cervelo R3, for about a year and have been riding it on the standard fit the shop provided. Granted the bike fit pretty well, but on longer rides I felt my shoulders and back starting to hurt a bit. One option was to just suck it up and keep riding, but given that  I just had knee surgery for a completely preventable running injury, I was determined to be kind to my body.

I did a bit of online research and came across the Retül dynamic bike fit system. Instead of taking fit measurements while the cyclist is at rest or analyzing two dimensional video, the Retül system captures realtime 3-D measurements while the cyclist is in motion. These measurements are taken under different stress levels, from easy efforts to hard pulls, so any changes in form can be detected. The data are then combined and immediately displayed in an easy-to-use software interface. The fitting expert and rider can then use these numbers to discuss and implement changes in the bike fit.

On paper, this sounded like a great idea so I looked around for a local fitting expert. There are a few shops in the area that offer the service, most priced in the range Retül recommends and one quite outrageously priced about twice as much. I was most intrigued by Revolution Cycles in Clarendon that has a Physical Therapist with a doctorate degree as their Retül fit expert. Having experienced knee problems significant enough to require surgery, a trained medical eye watching over my movements on the bike was a huge plus. I checked out the website and turns out the PT is part of Fast Track Physical Therapy, which has a close relationship with my new triathlon team, Team Z. I was sold!

Steve Berkey, the DPT fit expert, was very responsive to my emails and I showed up at the shop for a 2.5 hour fit sessions this past Saturday. Steve quickly setup my bike on a trainer that sat on a revolving platform (so measurements can be taken on both sides), and was kind enough to have some fans going to keep me cool. All the measurements were going to be recorded on his laptop, which in turn was hooked up to a large TV screen so I could also see and review the numbers.

We started out by talking about my riding aspirations and I told Steve that I loved climbing (though not particularly good at it!), but was also interested in seeing whether my bike could be fitted with TT bars so I could get more aero in triathlons. We discussed the possibility of switching out my regular seatpost for a Profile Design Fast Forward seatpost, which would put me a in more forward position conducive to time trials.

However, Steve cautioned that the R3 isn't really meant for aero bars since the natural geometry of the bike puts the rider further back on the machine so we'd be fighting the geometry in order to get a comfortable aero position without hyper-extended arms. Of course anyone can slap on aero bars on the bike but this would eventually mean a very uncomfortable riding position (think plank pose!).

With these goals and limitations in mind, I hopped on the bike and Steve started attaching the Retül sensors on my right side (each side is measured separately). The sensors are basically the size of a quarter, strung out on a thin cord, and attach to your wrist, forearm, arm socket, hip socket, knee, and shoe. They attach with small Velcro stickers and are fairly easy and painless to put on and remove. Data from these sensors are then wirelessly transmitted to the laptop.

Once all the sensors were attached, I truly looked like bionic man on a bike (note this picture was taken a bit later in the testing as the sensors are attached to my left side and I am noticeably tired!):

The fit process can best be described as a series of testing, adjusting, re-testing, re-adjusting, and so on till the most optimal fit is achieved. The Retül system combines years of research on efficient body positioning and joint flexion to come up with recommended measures and angles. The fitter can then make adjustments on the bike to try and get within a variance band of these optimal numbers. Such micro-adjustments are simply not possible with the naked eye since the angle at rest is different than the angle in motion (for example, moving slightly forward or back on the saddle changes the angles at your knee joint, hip joint, armpit, and elbow!).

Steve had me warm up for a bit and then took three 15 second measurements under increasing stress levels. Interestingly and luckily, my form did not change much with increasing stress, which was great news! However, my knee angle (i.e. angle between the top leg and bottom leg measured at the knee) was a little bit low (i.e. by a few degrees), so here Steve is adjusting my saddle height by bringing it down just a millimeter or so to increase the angle.

Steve also noted that I was a bit overextended on the top part of my body, and lowering the saddle would help in that regard too. He moved my saddle forward as well and just to boot, he added a small spacer under my handle bars to bring them up just a tad.

I immediately noticed less tension in my upper back and less weight on my arms under this new position. I couldn't believe that such a tiny micro-adjustment could have such a noticeable impact. But I knew the real test would be on the road on an extended ride. I had a 40 mile ride planned with Team Z the following day so I was excited.

Back to the Retül testing, the output from the testing was displayed on a large flat-screen TV and was easy for me to read:

The most interesting part of the testing came when we switched the sensors to my left side. See the blown up image of my testing data below. The columns are a bit misaligned but the second column, "01_right" is my baseline measurement for the right side and the last column, "05_right" is my final position on the right side before we switched to the left. The most valid comparison between left and right is between the last two columns, that is the final position on the right vs. the baseline position on left which was measured before any further adjustments.

Focus on the orange oval first. Holy mackerel! On the right side, my knee is 2mm forward of the foot, and on the left my knee is 26mm BEHIND the foot (i.e. -26mm). This is a substantial imbalance. Several theories could explain this:

(a) My right butt cheek is bigger than my left butt cheek so I am naturally misaligned. Nope, my butt is perfectly symmetrical, thank you very much.

(b) There is some internal misalignment at the joints or of the bones, which is causing my body to rotate towards the left. Here is where having a PT doing the fit really helped. Steve did a quick exam and concluded that I am not misaligned.

(c) I do not sit symmetrically on the saddle. This is most likely the culprit and Steve agreed.

So we decided to lower the saddle a tiny bit more to try and get the numbers on both sides more aligned. We couldn't move the saddle any more forward as it was already at the most forward position possible.

On the knee alignment, the golden rule is that the absolute value of the knee offset should not be greater than 10mm. My baseline offset was 2mm + |-26mm| = 28mm, and hence way way off!

By lowering the saddle a couple times, we managed to get my left-side offset down from -26mm to -18mm (the blue circle). Lowering the saddle any further would jeopardize others measurements so we stopped there. We decided to forgo the Fast Forward seatpost option as this would not move my knee forward enough to really benefit from a TT position, and it would worsen some of my other numbers. So why jeopardize my road bike fit in favor of a so-so kinda ok TT position.

And that was it, the sweet spot -- the most efficient fit for my body on my bike. It wasn't perfect but it was my most efficient, injury-preventing position.

So the fit was done and I hopped off the bike and grabbed an energy bar and some water. Steve finished tightening all the bolts on the bike and I thought we were done.

But not so! The coolest part of the fit was yet to come. Steve grabbed this wii-remote type probe and started poking my bike in different places. After a minute I realized he was electronically measuring my bike fit dimensions. This was way cool. Every time he touched the probe, a screen would pop up on the TV display with a real-time image of my bike. This is how it looked:

And here is Steve with the probe:

At the end of this process, I had my entire bike fit dimensions clearly illustrated in an easy-to-read printout:

How is this useful, you might ask? Well for one, you always have your optimal fit measures in hand. Suppose your saddle slips or you have to swap out stems or handlebars, you know what positions to set.

Second, and most useful for those of us who travel a lot, these detailed fit measures can be a great tool to setup a rental bike in far away places. Most places you go there is bound to be a decent bike shop, some that rent road bikes. You can send this pdf file to them in advance and they'll setup your rental bike to exactly match your fit. How cool is that!!!

Obviously having your own bike is the best option, but you do have to lug around a large bike case and pay hefty airline fees. For short trips, remote locations (where only small aircraft fly), or traveling with family, this seems to be a really really good option.

Most of my travel is for work and I tend to hit multiple countries in the same trip. I have been willing to lug around my large bike case and pay airline fees because I love the feel of my own bike. Now I can very closely match that same feeling for the same price the airline charges for carrying my bike (the Retül cost me $250). Note the Retül is a one-time fee and bike case fees are recurring every time you travel.

The last part was testing out the fit on the road on a long ride. I signed up for the 38 mile Sunday ride with Team Z and got to the start a bit late. This meant that I had to catch up to my group for the first few miles. My pedalling felt very smooth and I didn't feel any pain in my shoulders or back despite having to hammer in the beginning. I finished the 38 miles very satisfied with my bike fit.

I would highly recommend a Retül fit with Steve. For me, it was $250 well spent.

Here is my shortlist of Retül's pros and cons:

- Dynamic fit -- dialed in by how your body moves on the bike rather than by how it sits
- Specific bike fit measurements
- Great way to optimize fit on rental/spare bikes

- None really. The only thing I can say is that perhaps your regular bike fitter got it right or very close. But, there is always potential for tiny improvements which can add up over time to help prevent injury and/or improve efficiency.
- A bit pricey... This will vary from person to person, but for me this was a great bang-for-the-buck. Just the peace of mind from knowing I am positioned as efficiently as I can be is worth a lot.

1 comment:

  1. On your knee measurements being different, another reason could be the Velcro stickers could be not in exactly the same spot on either leg!?