If you’re interested enough in bikefitting to have discovered this site, the chances are you’ve done a bit of digging around the subject, maybe with a view to getting fitted, or maybe with a view to trying to find some guidance that can help sort your own position. In which case, you may well have come across the acronym KOPS, together with debate about the validity of using KOPS as a way of divining your saddle setback, in other words your fore and aft position on the bike.
For those who haven’t come across the term, let me fire some explanatory words at you. KOPS stands for Knee Over Pedal Spindle, and refers to a bikefitting protocol which would have you set your saddle in such a position that your knee is directly over the pedal when the crank arm is horizontal and pointing forwards. Actually that’s not strictly accurate, as some methods have you place the front of the tibial tuberosity – the lumpy bit below your kneecap – directly over the spindle, others will have you align the front of the patella itself with the end of the crank arm. Either way, results are broadly similar in placing the hinge point of your knee joint slightly aft of the pedal spindle at the horizontal, and therefore directly over the pedal at the point during which maximum force is being exerted, around 110-120 degrees from top dead centre. They’re also broadly similar in not doing this terribly accurately, because patellas and tibial tuberosities vary markedly in size and shape.
Anyway, the finer details aren’t really to the point. It’s an idea that was first formalised in a manual, imaginatively titled Cycling, produced by CONI, the Italian Olympic Committee back in 1968, and over the years gained wide acceptance and validity through sheer repetition, and went on to become the basis for many different fitting systems. It’s an easy technique to learn and understand, and there’s a certain amount of common sense to the approach. Intuition would lead you to conclude pushing vertically down through the pedal, rather like climbing a ladder, seems sensible, so yeah, why not?
The flaw with this theory, though, is that there’s no particular biomechanical basis to support the idea that pushing down is any more effective than pushing in any other direction, providing that the moment of force is roughly perpendicular to the crank arm, i.e. approximately tangental to the rotational direction of the crank, with the rider’s body appropriately angled at the hips to achieve this efficiently. Simple proof of this can be seen by looking at a rider on a recumbent bicycle, where maximum force is being applied in a more-or-less horizontal plane rather than a vertical one, or to a lesser extent on a time trial bike where the rider is pushing down and back, but crucially still at a tangent to the rotational path of the cranks. In both these contrasting styles of bicycle, what happens is that the rider has, effectively, been rotated around the bottom bracket, but their fundamental body shape and angular relationship between torso and femur are actually pretty similar to those of a rider in a conventional position.
The most famous demolition of knee-over-pedal came courtesy of Keith Bontrager in an article published around twenty years ago, entitled The Myth of KOPS, which goes into great detail to demonstrate what I have tried to outline in a single paragraph. It’s a very convincing argument against relying on the knee to pedal juxtaposition prescribed by KOPS to produce optimum biomechanical pedalling efficiency, and I have no issue with it on that basis, but here’s the kicker: nowhere in the CONI manual did it say that this relationship was to do with biomechanical efficiency.
And that’s because it wasn’t. Rather, it was using the knee to pedal relationship as a means of setting the rider’s centre of gravity in approximately the right position on the bike, a position that was not too fatiguing for the rider to maintain, and that also promoted good weight distribution between front and rear wheels. Okay, so let’s not worry that KOPS isn’t a particularly effective way of achieving this objective either; the point is that debunking the theory on the grounds of it having no biomechanical basis is simply saying that it doesn’t prove something that it was never intended to prove in the first place. Its a bit like saying Mark Cavendish has got his training wrong because he’s a rubbish climber (although he’s still better than you, by the way).
In other words the Myth of KOPS is, in itself, a myth.