Daily Archives: 2008/03/04

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Extensiones S-BEND funcionalidad uv fashion

He encontrado un articulo que me parece muy interesante.

Desde que tengo el acople HED CLIP LITE vengo dandole vueltas a la posicion de la muñeca. Me pasa que para llevar la muñeca recta tengo que inclinar el acople hacia arriba.

Este articulo explica el porque no son tan recomendable estas barras como las anteriores.
Cada uno que opine.
Lo pongo en ingles porque los traducctores hacen muchas chapuzas.

“S” bend aero extensions in use.

Since the popular introduction of the aerobar in 1987 there has been a constant evolution of design in elbow rest, aerodynamic handlebars. A recent change in aerobar design is the “S” bend extension. “S” bends are the straight tipped slightly curved extensions that are mostly parallel with the ground. There are many versions of “S” bends with different nomenclature for some specific configurations. Visiontech refers to their mostly horizontal bend bars as an “R” bend for “Race Bend”. There are even straight extensions with no bend from companies like Oval.

The thinking behind the “S” bend extension comes from time trialing, not triathlon. Time trialists in stage races like the Tour de France often pull up on their aerobar extensions to stabilize their torso against a brutishly powerful pedal stroke. This pedaling technique provides extra leverage but at a cost to comfort and economy. It takes significant effort to stabilize the upper body using an “S” bend style extension. Top professional time trail riders often average over 400 watts power output in a time trial stage as compared to around 200 watts for a good age group triathlete.

As we began to fit customers two years ago using “S” bend style extensions we discovered they were less comfortable and required more effort to use than older, more conventional upward bend “Ski” extension aerobars. In many cases bike handling and shifter ergonomics suffered when using “S” bends.

The reason why “S” bends tend to work for time trialists at the professional level but not recreational level triathletes has to do with the differences in how we use our aerobars. Simply put:

  • Time trial riders pull up forcefully on their aerobar extensions to brace their torso against a powerful pedal stroke.

  • Triathletes lean on aerobars for skeletal support to reduce muscular work load in addition to improving aerodynamics.

Based on our experience fitting, training and racing with “S” bends, they have proven to actually be less comfortable and efficient that the more traditional, upturned ski bend style aerobar. “S” are a particularly poor choice for entry level triathletes and Ironman distance triathletes due to the reduced comfort and compromised bike handling.

“S” bend extensions are flatter than previous traditional “ski” bend aerobars.

“S” bends put shifters at awkward angles making them more difficult to use.

Riders using “S” bends frequently release their grip to relax their forearms. This reduces control of the handlebars.

There are many varieties of aerobar extensions for different riding styles.

A traditional ski bend style aerobar is best for forearm posture in triathlons, especially long distance events.

The differences in how triathletes and time trialists use their aerobars are substantial, especially in longer events such as Ironman or Half Ironman.

When a professional cyclist like Ivan Basso or Lance Armstrong leaves the start ramp in a time trial stage of the Tour de France they are exerting enormous forces on the bike to get up to speed and maintain speed on rolling terrain and in windy conditions. These professional cyclists generate double the power output of a talented age group triathlete. To provide a powerful base for pedaling time trial riders try to hold their upper bodies rigid against the pedaling forces of their legs. Pulling up on their extensions and pushing down on their elbow pads they are bracing their core against the forces of their legs turning the cranks. This riding style is based in power and relies on substantial muscular involvement of the upper body including large muscles like the latissimus dorsi. There is a substantial physiological cost to this effort but in a short time trial with no run leg afterward the time trial rider can afford the cost.

Triathletes have a different enough riding style that they will likely not benefit from “S” bends. While even the best triathlon cyclists like Normann Stadler, Torbjorn Sindballe generate substantial power they are more reliant on the aerobars for skeletal support of the upper torso. Especially in longer events such as Ironman triathletes tend to use the aerobars for support of the torso. Triathletes do use the aerobars as an anchor and fulcrum against which to brace themselves for pedaling forces. For this reason and others the “S” bend aerobar is not optimal for most triathlon cyclists.

From an anatomical perspective an “S” bend aerobar is less comfortable than traditional up turned, ski bend aero extensions. “S” bends place a significant adduction on the inner/medial surface of the wrist. We visited Dr. Marcus Imsande, a specialist in treating sports injuries, to shoot X-rays of my arms holding various bends of aerobars. The implications are clear: “S” bends force the rider to bend the wrist at an uncomfortable angle in order to maintain grip on the aerobars. This causes the forearm to be less comfortable and fatigue more quickly.

Additionally, the ergonomics of the bar-end mounted shift lever are extremely poor in “S” bends, with the shift lever pointing directly at the ground in the 11 or 12 tooth cog or hardest gear position. This orientation of the shift lever on “S” bends makes shifting to and from the largest gears awkward and uncomfortable. Athletes generally have to completely release their grip of the aero extension on “S” bends to pull the shift lever back toward them shifting to an easier gear.

Finally, there is even a case to be made that straighter tipped, “S” bend extensions are more difficult to control and exert a negative affect on bike handling. As we have observed on the road and during indoor trainer rides athletes tend to recognize the uncomfortable wrist postures associated with “S” bends and release their grip on the forward, straight extension to relax their hand and forearm. This reduces stress on the forearm but also means the athlete no longer has a firm grasp of the handlebars. Some athletes do this on “S” bends without realizing it in an attempt to make their forearms more comfortable. If the athlete were to hit a chuckhole or have to steer quickly in an emergency the implications of not having a firm grasp of the handlebars are serious.

In 2007 a number of bike manufacturers have speced “S” bend aerobars on their triathlon bikes. This is a less than optimal configuration for most triathletes because of the reduced forearm comfort, poor shifter ergonomics and potentially compromised bike handling induced by using “S” bends as opposed to up turned ski bend extensions. All of these aerobar extensions can be easily substituted with a more traditional, comfortable, safer up-turned ski bend extension at a minor cost. While many athletes may find the “S” bend aerobars racy looking since they mimic the look of Tour de France bikes, this is not a case of form follows function. “S” bends do look cool and seem to present a smaller frontal area, at least by appearances. The problem is they simply aren’t practical for most triathletes, especially newer triathletes and long distance triathletes.

During our survey of “S” bend aerobars we tried aerobar configurations from nearly every manufacturer available, building up numerous bikes and training and racing several hundred miles through 2005 and 2006 to determine the optimal configuration for the majority of riders. While every rider and fit is unique, more riders will benefit optimally from a traditional upturned ski bend style aerobar than the newer “S” bends. In the case of “S” bends, they seem to be more fashion than function.

The athlete uses the aerobars as skeletal support for the torso while maintaining a powerful, aerodynamic position with ski bends.

Dr. Marcus Imsande views X-rays of a rider holding various aerobar extensions.

The extreme adduction of the wrist and hand is apparent in this X-ray using “S” bends.

Time trialists rely on muscles like the latissimus dorsi to stabilize their torso while pulling on their “S” bend aerobars.

“S” bend on the left, traditional ski bend aerobar onthe right. You don’t have to be a doctor to see which posture will be more comfortable and relaxed.

Most high quality aerobars, such as the Zipp Vukka, have a variety of extensions for optimal fitting and comfort.