Technique: Can aero bar performance?
By Nick Morgan | Friday, August 29, 2008 12.00pm
Some schools of thought believe that the aero position may hinder breathing Paul Smith
The growing popularity of triathlon and the aero position has changed the shape of road biking, but adopting the right posture isn’t quite that simple. We look at the arguments for when the aero position is appropriate and for whom.
What is the aero position or 'tuck' ?
The aero position is achieved by sitting back on the seat and folding from the navel so your trunk is parallel with the ground. The elbows are kept in tight at an angle approaching 90 degrees (don’t push the hands too far forward) and the head is down with the eyes looking forward and down. The hand grip on the aero bars should be relaxed.
What are the advantages of using the aero position?
Virtually all studies show it’s more aerodynamic than the standard upright position or a dropped position with hands on the drop bars and with the back arched. For example, French researchers from Besancon found it reduces frontal area by 12.8 per cent compared to upright. That’s enough to make ﬁve to seven minutes difference in a 40k time trial. A huge advantage, but not the end of the story, as French scientist Francois Hug explains.
“When deciding on posture you need to ask three questions.
- Do you want to reduce frontal area?
- Do you want to optimise pedalling technique?
- Or do you want to minimise fatigue?
For example, when going uphill, reducing frontal area isn’t such a priority because wind resistance is proportional to speed, so an upright position is better.”
Indeed, even on the ﬂat the evidence isn’t clear cut because aerodynamic advantages must be weighed against possible physiological disadvantages. Initial studies noted few physiological differences between positions and some even discovered that the aero position conferred a cardiovascular advantage. But recently scientists have started to question this.
Francois Hug’s research shows that for a given power output, the aero position causes cyclists to push more on the pedals because they pull up less. This causes an efﬁciency drop as the knee and hip extensors are forced to work harder. He concluded that the aerodynamic gains still far outweigh these losses but that riders should practice their pedal pull if they want to maximise the beneﬁts.
The possible disadvantages of using aero bars
Other authors have questioned the validity of the aero position for longer rides and inexperienced riders.
A team from the University of British Columbia believe that although there’s evidence of cardiovascular advantage, this may be counter-balanced or even outweighed by ventilatory restrictions. Dropping too low can cramp the lungs, making breathing faster and shallower. They also suggest previous results must be treated with caution because they involved short-duration/ intermittent cycling.
The aero position may be less suitable for longer rides, they argue, as the ventilatory discomfort takes its toll. The same researchers also tested beginners and found that contrary to studies using experienced riders, the time it took to fatigue using the aero position was actually shorter.
“In untrained subjects performing with maximal effort, the upright position permits greater VO2, ventilation, heart rate, and workload maxima,” they said. “This means exercise cycling may be less costly in the upright position.”
So while it’s clear that the aero position does have its advantages, you have to know when and how to use it, otherwise you may actually end up riding slower.
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