En fixed gear sykkel (fastnav) er en sykkel hvor drevet bak er skrudd fast på navet uten frihjulsnav. Så lenge hjulet går rundt går også kranken rundt og omvendt. En fixed gear sykkel kan også sykles baklengs...

Sunday, April 25, 2010

Wednesday, April 21, 2010

Klein Adroit Black Storm Edition

Finn Haug sin vakre Klein Adroit fixie!


Thursday, April 08, 2010

Why Fixies are Bad for Your Knees

Why Fixies are Bad for Your Knees

Fixies, for the uninitiated, are fixed-gear bikes, which as you may have gathered are just bikes. However, rather than have multiple gears, they have just one, and rather than being able to spin your feet backwards without effect, doing so on a fixie will actually propel the wheel in reverse. This gives the rider additional control of the bike when, ironically enough, it is sitting still and helps him to stay upright on a racing track or at a traffic light. The main benefit for non-racers and non-couriers (who account for perhaps all but twelve actual fixie riders) is that it makes them look cool. Plus it allows them to pretty up their bikes by removing annoying visual clutter… such as brakes.

Again, fixed-gear bikes are just bikes, and the injuries they cause are essentially the same as all other bikes. Accidents and poorly adjusted equipment (seats, handlebars, cranks, and pedals) are issues for all cyclists. The main difference here is that a bicycle with gears and brakes allows the rider to dramatically decrease the likelihood of knee injuries, whereas a fixie, especially those without brakes, does not. And in fact, they are more likely to cause and/or aggravate the most common and least curable knee related cycling injury.

Frequency and type of cycling related knee injuries

As the following excerpts will make clear, knee pain is present in up to 65% of all cyclists, with one specific problem accounting for the majority of those problems and for 25% of all injuries to all cyclists. (Note that although it is called by various names, it is the same diagnosis, which you can read about at wikipedia’s article on Chondromalacia patellae.) That means that a quarter of all injuries for cyclists are the direct result of one problem that is directly related to high-gear, low-cadence pedaling.

Excerpted from:
Knee Pain and Bicycling: Fitting Concepts for Clinicians
CPT Chad Asplund, MD; COL Patrick St Pierre, MD

“Knee pain is the most common lower-extremity overuse problem in cyclists. (7,8) In one recreational long-distance bicycling tour, 65% of all riders reported knee pain. (9) Another study (10) of more than 500 recreational cyclists indicated that almost 42% of all riders experienced overuse knee pain. While major problems such as fractures, dislocations, and ligament ruptures usually occur only after major trauma, overuse injuries are much more common….

“Gearing is a method of overcoming resistance that allows the cyclist to pedal comfortably at a uniform cadence to improve pedaling efficiency. Higher gears result in higher resistance, and lower gearing provides less resistance….

“Chondromalacia, characterized by pain…, is described as a grating sensation… that worsens with climbing, squatting, or prolonged sitting…. During cycling, the pain is precipitated by riding up hills or when the rider pushes higher gears with a slow pedal cadence.

The citations referenced above are:
7. Holmes JC, Pruitt AL, Whalen NJ: Lower extremity overuse in bicycling. Clin Sports Med 1994;13(1):187-205
8. Holmes JC, Pruitt AL, Whalen NJ: Lower extremity overuse in bicycling. Clin Sports Med 1994;13(1):187-205
9. Dannenberg AL, Needle S, Mullady D, et al: Predictors of injury among 1638 riders in a recreational long-distance bicycle tour: Cycle Across Maryland. Am J Sports Med 1996;24(6):747-753
10. Wilber CA, Holland GJ, Madison RE, et al: An epidemiological analysis of overuse injuries among recreational cyclists. Int J Sports Med 1995;16(3):201-206

And from Sports Injury Bulletin:
Cyclists’ knee injuries – patellofemoral syndrome
Owen Anderson, Ph.D. (exercise physiologist & training expert)

“…patellofemoral syndrome, is the most common cycling injury, accounting for around 25% of all cycling problems (‘The biomechanics of cycling,’ In: Holloszy JO, ed., Exercise and Sports Science Reviews, Baltimore, Md: Williams & Wilkins; pp. 127-167 1991).

“…Training factors linked with patellofemoral pain include hill training, cycling with high gears at a low cadence, and a sudden increase in training volume.”

Description, cause, and severity of the most common injury

Again, the excerpts below describe a condition that is the explicit result of high-gear, low-cadence pedaling. It is often mentioned that minor abnormalities in a person’s knees or in their style of pedaling are often the initial cause of the early stages of the problem, and that is true for all styles of bikes. At that point, the problem is still treatable. However, in cyclists it is the high pressure on the knees from high gears that aggravates the problem and causes permanent damage, and in fact it very commonly causes that damage on its own, without the presence of abnormalities or poor pedaling technique.

Excerpted from:
Knee Pain and Cycling
by Joshua Cohen, PT MS
(At 63xc.com, a now defunct off-road fixed-gear website. Joshua Cohen is a physical therapist and author with a focus on biomechanical issues related to cycling.)

“One of the most common of these conditions is chondromalacia patella. This affects the rear of the kneecap. In healthy knees, the rear of the kneecap is smooth in order to allow it to glide across the other bones which make up the knee joint. In chondromalacia, excessive contact pressure between the kneecap and the knee joint over time causes this smooth surface to break down. As the condition progresses there is often an increase in knee pain, especially in forceful extensions of the knee during activities like climbing stairs–or pushing big gears at low cadence.

Gearing choices can become an important variable in preventing the progression of chondromalacia patella. When the leg is forcefully extended, as during a cyclist’s power stoke, the knee cap acts as a pulley to transfer the large forces of the quads across the knee joint to the tibia (one of the lower leg bones). As a result, a component of the tendon forces pulls the knee towards the knee joint, greatly increasing the pressure on the back of the kneecap. This pressure can wear down the joint surfaces. Normally, a thin layer of slippery fluid lubricates the joint and prevents wear. However, during slow, forceful extensions (think big chainring grinding uphill) this fluid becomes displaced and the joint loses much of its lubrication. This is not good for your knees or pistons!

Keeping a higher cadence will help to reduce the pressure of the knee cap against the knee joint, allowing the lubricating fluid to remain between the joint surfaces where it belongs, and so lessening the risk of joint surface breakdown. Cadences above 80rpm are generally better for your joints than knee-mashing 60 rpm cadences. Remember to choose your gear inches wisely and take into consideration the terrain and your ability to power your gear to maintain a relatively high cadence.”

Again from Sports Injury Bulletin:
Cyclists’ knee injuries – patellofemoral syndrome
Owen Anderson, Ph.D. (exercise physiologist & training expert)

“…Biomechanical abnormalities of the patellofemoral complex (the knee cap, the
femur, and their associated muscle and connective tissues), in conjunction with
strenuous training, are believed to be responsible for most cases of chronic
knee pain in cyclists.

“…As the cartilage breaks down, extra pressure is
then put on the bones which come together at the knee joint, producing bone pain
and inflammation.

“…note that these conservative and traditional
treatments only decrease symptoms temporarily. If you have patellofemoral pain
and ‘cure’ yourself with rest and ice – and then return to the kind of training
you were carrying out before the pain arose, in most cases the discomfort will
come right back again. In one study of conservative patellofemoral-pain
treatment which included a long follow-up, it was found that only 30% of
patients remained symptom free after 12 months (’Management of chondromalacia
patellae: a long term solution,’ Aust J Physiother, vol. 32(4), pp. 215-222,
1986). The reason for this, of course, is that the rest, ice, drugs, and
ultrasound do not correct the biomechanical deficiency or lack of strength which
is actually creating the problem….Cycling techniques which decrease
patellofemoral joint-reaction forces should be emphasised, at least at first;
these include spinning, using low rather than high gears, and (as mentioned)
avoiding excessive amounts of hill training.”

Fixed-gear-specific issues

All of the above information is equally true of any style of bike, however there are two reason that fixie riders are more susceptible to injury, both of them related to higher pressure on the knees. In the first place, it is simply not possible to pedal fast enough during acceleration and hill climbing. And in the case of fixies without brakes, the “backwards” pedaling causes even higher stresses on the knees.

A normal bike with gears allows for a start with fast pedal spinning in a low gear and gradual increase in gear size as speed grows. At all points, it is at least possible to maintain a fast cadence and eliminate high pressure on the knees. However, unless a fixed-gear rider has a personal manservant who tows him behind the Bentley until cruising speed is achieved, he must — yes, must — start and accelerate in far too low a gear, and his knees are under a coresponding amount of pressure. The very same is true of hill climbing. So unless a fixie enthusiast rides for very long stretches on perfectly flat terrain with no traffic and no intersections and no head wind and no hills or altitude changes whatsoever, he will spend a fairly significant amount of his time in a gear that is far too high and requires that he put inevitably damaging pressure on his knees.

Since fixies are primarily an urban fad, not yet all the rage on the plains of Nebraska or the salt flats of western Utah, that means that essentially all people who ride fixed-gear bikes must spend a lot of their time starting at lights, cruising too slowly in traffic or through intersections, and climbing the inevitable hills. In short, fixie riders are at higher risk for the most common knee-related cycling injury specifically because of the lack of gears and because of where the bikes are generally ridden.

The other fixed-gear-specific issue is not universal, but is still quite common. In particular, it is the fashion among fixie riders to strip their bikes of unattractive paraphernalia, unfortunately including their brakes. To slow down, those riders must “pedal backwards,” or apply pressure in the reverse direction so that their bike gradually slows. That means that in addition to acceleration and hill climbing, brakeless fixie riders are also grinding down their knee-caps as they slow down and sometimes even as they descend hills.

Logically speaking, that would almost double the amount of time spent in the wrong gear and the amount of high pressure on the riders knees. In fact, however, studies have shown that “pedaling backwards” exerts higher pressure on the joint than the normal direction. So that means that the additional strain on a brakeless fixie rider’s knees is more than double.

Excerpted from:
Cycling for Knee Rehabilitation
by Karen Hambly BSc MCSP (Sports Scientist/Physiotherapist)

“… Changing the direction of pedaling alters the relative contributions that the
different muscles make to the activity.

“When pedalling backwards,
compared to forward pedalling, the quadriceps are even more active relative to
the hamstrings (Refs 2 & 6). This increased quadriceps activity puts even
greater stress on the patellofemoral joint ….”

Citations referenced
above are:
2. Bressel, E. (2001) Influence of ergometer pedaling direction
on peak patellofemoral joint forces. Clin Biomech 16(5):431-437.
6. Neptune,
R.R. & Kautz, S.A. (2000) Knee joint loading in forward versus backward
pedaling: Implications for rehabilitation strategies. Clin Biomech

And again from Sports Injury Bulletin:
What’s the best way to treat anterior cruciate ligament (ACL) injuries?
Owen Anderson, Ph.D. (exercise physiologist & training expert)

“…new research carried out by R. Neptune and S. Kautz at the Palo Alto Health
Care System in Palo Alto, California, reveals that backward pedalling may indeed
be useful for individuals with certain knee disorders – but is contradicted in
other cases (‘Knee joint loading in forward versus backward pedalling:
implications for rehabilitation strategies,’ Clin Biomech (Bristol, Avon), Aug;
Volume 15(7), pp. 528-35, 2000). When they quantified tibiofemoral and
patellofemoral joint-reaction forces, Neptune and Kautz found that lower
tibiofemoral compressive loads – but higher patellofemoral compressive loads –
were observed in backward pedalling, compared with normal cycling.

“…reverse cycling can actually produce greater compressive forces
between the patella and tibia, compared with normal cycling….”


Across the board, it is universally accepted by medical experts that high-gear, low-cadence pedaling has a high likelihood of causing knee pain and permanent injury. The main preventative measure as well as primary remedy for that problem is low-gear, high-cadence riding, which is only possible with the ability to change to appropriate gears throughout a ride. Fixed-gear riders are unable to avail themselves of that remedy, and because of that, they experience more frequent and higher pressures on the knee than a rider on a bike with gears. To add to the problem, the common decision to remove brakes and use the legs for stopping multiplies the stresses on the knees, both by increasing the time that they’re under pressure and by increasing the magnitude of the forces involved.

So, yes indeed, fixies are really really bad for your knees...

Source: http://yamabushi.wordpress.com/

Tuesday, April 06, 2010

Red Bull mini drome

This is the Red Bull mini drome. Auckland, New Zealand, 4th of april 2010.