etween positions for Vo2 using a repeated measures analysis of variance. Other variables did not differ between groups (figs 1 and 2).
Gross mechanical efficiency
The %GME increased as exercise progressed in both positions. There was a significantly higher value obtained for the upright position at 50 and 100 W, which was not significant at 150 W.
Physiological response to the aero position is not well understood, and previous results using “trained” participants are inconsistent. The conflict of previous results may be due to different experimental controls, experience of the cyclists, or the adaptation of training. To our knowledge, no studies have investigated the response of untrained cyclists to the variation of positions. For this reason, this study is unique in that: participants were unfamiliar with aerobars and the crouched position; results were obtained using standardised positions and several different exercise intensities and durations were tested.
In the maximal exercise testing, significant differences were found in Vo2max, Ve, heart rate maximum, and maximal workload. The crouched aero position was associated with smaller increases in tidal volume compared with the upright position. Subsequent reliance on increased breathing frequency was associated with earlier termination of exercise. Origenes et al3 believed that cyclists in the aero position should show a higher breathing frequency but smaller tidal volume and therefore higher inspiratory flows caused by a possible restriction imposed by the position.
Franke et al2 found that the aero position gave higher stroke volume at rest resulting from an increased pre-load. They did not find this phenomenon during exercise. If the assumption that the aero position provides a greater stroke volume is true, but heart rate remains the same in both positions, one would expect to see some advantages resulting from greater cardiac output. However, this may be difficult to measure non-invasively. The crouched aerobar position may impair the ability to increase tidal volume, and subsequent increased breathing frequency may lead to earlier termination of exercise compared with the upright position. It may be that the combination of limitations imposed by restricted ventilation, increased energy cost, and the subsequent resultant fatigue outweigh any cardiovascular advantages that may be present in the aero position.
In the steady state exercise, physiological responses parallelled those seen in the maximal exercise tests. Overall, there was a trend towards better respiratory response in the upright position as reflected by a larger tidal volume and lower breathing frequency. Although not statistically significant, a trend was observed in the respiratory exchange ratio, which was higher in the aero than the upright position for the same absolute workload. This indicates that the participants worked harder in the aero position and is supported by the significantly greater %GME observed in the upright position at 50 and 100 W. The only significant differences found between positions were for Vo2 and GME, with the upright cyclists having greater Vo2 and %GME.
This study is novel in that all participants were unfamiliar with cycling and therefore with the use of aerobars. Training may develop adaptations to the near horizontal position. In previous studies of trained cyclists,1–3,7–9,11 time to fatigue was found to be shorter in riders in the aero position. Berry et al1 recommended that cyclists who raced with aerobars should also train with aerobars. Also, Gnehm et al8 observed that elite cyclists suffered a disadvantage in the aero position.
On the other hand, Sheel et al7 observed an advantage for cyclists in the aero position compared with the upright position during a submaximal exercise protocol. The differences between studies may result from the fact that the participants in the study of Sheel et al were trained athletes experienced in using aerobars for at least one year. Furthermore, the cyclists in that study did not use their own bicycle, and wind velocity was no