It's All In The Hips

Happy New Year! After a very enjoyable holiday season with family and friends, we've arrived in 2014. For me, that also means another birthday. I was fortunate enough to spend the day with some great people and Skype my family from Australia. It was a great day! I also received some unbelievable gifts, one of which I wanted to make the focus of this post.

The weather this season is truly embracing the quintessential meaning of winter; below freezing temperatures, icicles hanging from the roof, and snow covered roads. One morning, my stubbornness got me into some trouble when I was adamant about doing my usual ride. Unfortunately, I didn't have any of the appropriate attire, nor the necessary experience to protect myself on such a ride. Without going into too many details, I decided that the experience wasn't one I should repeat on a daily basis if I put any value in my health.

The solution, therefore, was to either use better equipment for outdoor rides or find a way to continue to train indoors during the winter. Luckily for me, my family was on the same wavelength! I received some amazing gifts, including a winter bib and riding jacket. I also received a set of rollers from my family in Australia and I absolutely love them.

The rollers are reasonably self-explanatory - the bike sits on top of the aluminum drums and as you pedal, the rollers provide the counter-rotation to the angular velocity of the wheel. Therefore, you are able to ride the bike without (too much) linear displacement. This is in contrast to other indoor trainers, which elevate and stabilize the rear wheel and provide the resistance to overcome. The two principal differences between these two systems of indoor training is that rollers provide no additional resistance (negligible friction and roller belts excluded) and require that the increase in intensity come from a combination gearing and cadence increases, whereas the trainers can provide significant resistance through magnetic forces, hydraulics etc. Secondly, since trainers stabilize the rider, the athlete can concentrate solely on applying power to the cranks, as opposed to the rollers where the rider must contend with balance issues and pedaling efficiency.

Prior to using my rollers, I had read many articles and reviews in which the authors expressed sincere disdain for training on rollers, simply because the learning curve was so steep and they were unable to cycle at an adequate intensity to make significant gains. And then there was this girl:

Always lean to the side you unclip.

So I began to wonder, "why are these experienced cyclists having such a difficult time riding on rollers when they can control a bike so well on the road?"
It turns out I am not the first person to ask this question. As far back as 1942, Arthur Jones began investigating the physics of bicycles and subsequent investigations revealed a great deal about the relationships between gyroscopic forces and 'trail' as well as stabilizing centrifugal forces. The physics of this is well understood, but the differences between riding a bike on the ground and riding on rollers remained in question.

Patricia Cleary and Pirooz Mohazzabi from the University of Wisconsin-Parkside investigated this topic in their article, On the stability of a bicycle on rollers (2011). A discussion of gyroscopic stabilizing effects, 'trail' and centrifugal forces are explained and I suggest you read it if this is of any interest to you. The following explanations can be found in their paper in far more detail.
A centrifugal force is essentially a reactionary force to the centripetal or 'center seeking' force. Therefore the centrifugal force is pushing an object in rotation away from the center of rotation. Consider a bicycle cornering: the rider leans into the corner, inducing a 'trail' and the resulting torque turning the wheel towards the center of the turn, thus beginning the bicycles curved path. As this happens, however, the centrifugal force acts to push the bicycle out of this path or pushes the bike to an upright position.

Now consider the same motion occurring on rollers, where a lean will not result in a rotational curvature and subsequent centrifugal force, since the drums do not permit any actual turning to occur. In this case, the trail is not counteracted by the centrifugal force and therefore will result in either falling off the rollers due to the wheel no longer being perpendicular to the rollers and simply riding off the side, or a counter-lean/steer by the rider to maintain the center of gravity above the contact points. This results in a lot of counter-leaning or counter-steering by the rider and can have the appearance and feeling of being far less stable.

An additional subtle difference on rollers is the exaggeration of the pneumatic tail, a result of the asymmetrical forces on the tire during turning. Because the rollers are a curved surface, this contact area is not necessarily always perpendicular to the wheel, thus creating additional torque to overcome.

So what does this mean for riding on rollers compared to the road? At a very basic level, it means that in order to remain stable on the bike while on the rollers, a rider must limit the amount of leaning and steering done. This seems an intuitive and a simple solution, but consider the causes of unwanted or accidental steering and leaning. Applying too much force to the handle bars, an uneven pedal stroke, tight back musculature causing a natural lean, an asymmetrical force generation between each leg, poor core control that results in a 'rocking' of the hips during the pedal stroke... all of these issues can easily cause a rider to feel extremely unstable when riding on rollers.

From my experience, the greatest benefit I have found from riding on rollers is the significant core control required. The most stable I feel when on the rollers is sitting upright, riding 'no-hands.' This eliminates accidental steering and allows me to control the bike through my core stabilizers. Unfortunately, this also puts me in a disadvantageous position for generating large power outputs, and so my training sees a majority of my time on the handlebars, always concentrating on a perfectly even and smooth pedal stroke with minimal hip imbalances by controlling my core musculature.
I believe this will help a great deal in making me a better cyclist when I am able to get back out on the road in a couple of months. I think everyone, whether you're a cyclist or not, could benefit from this kind of training if for no other reason than it forces core control like no other activity I have experienced...and it's unbelievably fun to ride your bike at 25 mph in your living room.

Please enter your email address to subscribe!

Posted with Blogsy