APR OCT MAR 13 1998 1999 2000 60 captures 26 Jan 98 - 11 Jun 13

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This is my best representation of what a standard road rider might look like, if he was to be represented as a stick figure, with lines intersecting at his ball-and-sockets, knees, and ankles.

If the bike is removed from underneath this road rider, and we consider him simply a system of levers, his femur is his most important lever for cycling. The effectiveness of this lever is largely determined by his hip angle, represented above as roughly a right angle scribed by two intersecting lines: the first between the ball and sockets of the hip and the the shoulder; the second from the hip to the pedal axle at the bottom of the pedal stroke.

If we assume that his choice of hip angle is related to his effort to seek a biomechanical "sweet spot" in his hip (the involved muscles being hip flexors and extenders, and gluteals), is it also reasonable to assume that as he changes to his time-trial bike-- flattening his back to assume a more aerodynamic position-- that he will try to preserve this hip angle?

Riders have always assumed a more aerodynamic position on their time-trial bikes. This phenomenon became that much more pronounced, however, with the addition of the aerodynamic handlebar. This technology effectively turned the standard road bike into a front recumbant, with the rider now able to "lay down" on the front of his bike, and support his upper body skeletally, instead of muscularly.

A position which would have taken years to perfect without the aero bar is now possible with a very short period of acclimatization. Even the best riders-- who through years of experience had achieved good body position without aero bars-- could, with aero bars, concentrate all their energy toward the pedal stroke, with an even flatter back than before.

However, if one simply adds aero bars to his bike, and therefore achieves a flatter back, the hip angle becomes more acute. The biomechanical "sweet spot" is now gone. What most pro triathletes have discovered, through a decade of riding with aero bars, is that the hip angle must be preserved.

It has been observed that a great number of pro triathletes ride with a "relative" seat angle of 78 degrees, plus or minus 2 degrees (the plus or minus depends on a variety of factors). When I say "relative" I am speaking of body position (forgetting for the moment the actual seat angle of the frame being ridden). One might achieve this relative angle through riding a frame designed specifically for it; one might adapt a standard frame with a special seat post; one might have no seat tube at all, as is the case with Softride frames; one might simply ride so far off the front of the saddle as to only barely be touching the nose. In each of these cases, the rider seeks to achieve that "sweet spot" in his hip angle, and in very many of these cases, the angle achieved would approximate a seat angle of 78 degrees.

Let us assume you have a road bike which you wish to adapt for time-trials (there are issues that come with such a retrofit. Short of having a large protractor how do you know what 78 degrees is? The graph above assumes that you are using a saddle of "average" length which is attached to an "average" seat post (which has its clamp seat slightly behind the center line of the post), and that the saddle is attached in the middle of the rails. If you measure, in a straight line, from center of the bottom bracket to the midpoint of the top of the saddle, the resulting number in the graph is that distance which the saddle should be in front, or behind, the bottom bracket, to achieve a relative seat angle of 78 degrees.

We recommend that you start with a relative seat angle of 78 degrees. If you are retrofitting a standard bike (see cautions mentioned above), there are seat posts designed for this. Be careful, though, many of them put you too far forward. Another alternative is a standard seat post which has the capacity to be turned around backward (not usually an original design feature). The best current seat post for this is the one made by Control Tech. These turned-around seatposts will put you 3cm-4cm forward, and putting your saddle all the way forward on the rails will give you another 2cm or so.

Now that your saddle is in the right place, your stem should be of a length which will allow for a right angle between your torso and your upper arm. You'll find that the great majority of pro triathletes, as well as the best pro cyclists, ride with this 90 degree angle, and you'll ride more comfortably, with less strain on your back.

That said, you may be one of those who need an angle slightly more obtuse than 90 degrees, meaning your stem needs to be a cm or so further forward. Candidates for this are those who have long legs (esp. femurs) and short torsos. The issue is out-of-the-saddle climbing. Remember that a person with a long femur will sit a little further back. If a right angle between torso and upper arm is desired, this will bring the armrests back in the same measure. If you have a short torso, this brings the armrests back even more. So, if you can imagine a vertical line passing through the armrest, this line will be quite a bit closer to a similar line passing through the bottom bracket for someone with a long femur and short torso. When such a person gets out of the saddle, it is possible that their kneecap will hit the back of the armrest. This is untenable, and requires the stem to be a little longer, moving the armrests out of the way. If this is your problem you should add the least amount of stem distance needed, i.e., hopefully the maximum you'll need to add is 1.5cm of extra stem length.

If you have set up your bike thus far following the above procedure, you now have a 78 degree relative seat angle, and your body has (roughly) right angles formed by:

• your torso and your upper arm, and...
• your hip. Remember, this hip angle is created by:
  • a line from your ball-and-socket joint from your hip to the ball-and-socket joint of your shoulder, and,
  • a line from the hip to the pedal axle at the bottom of the pedal stroke.

Eventually, if there are no structural limitations specific to you, this is a realistic range for armrest drop. Realize also that the most aggressive side of this range is where the most aggressively positioned pros have set themselves up. You must decide whether this is an appropriate position for you (some of the best riding triathletes in the world, e.g., Jurgen Zack and Spencer Smith, are on the less aggressive side of this range. As a general rule, the truly powerful riders tend to be somewhat less aggressively positioned, as they feel their power is compromised. There is something else these particularly powerful riders often have in common, and that is an armrest tilt peculiar to them.

Everyting above refers to riding in the aero position, but you'll occasionally have to ride out of that position, and this requires some thought to be given to the out-of-the-saddle hand positions, and also to how you're going to set your bike up for shifting. The latter is important, since riding with aero bars requires a different tactical approach, especially when out of the saddle.

Finally, notwithstanding all the formulas that so favor the aerodynamic aspect of speed in cycling, it is my belief based on a decade of fitting pros and age-group athletes alike, that there is nothing to be gained by sacrificing even one watt of power to achieve a more aero position. Biomechanics and ergonomics (comfort) are to be retained at all costs. That is not to say that an aerodynamic position is not to be desired, the entire exercise described in these pages is the attempt to find the most aerodynamic way to ride a bike: but not at the expense of power and comfort.

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