 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 not measured. Wind velocity is an important variable, as the aero position reduces the wind resistance.5 Our study investigated the physiological response while controlling for environmental factors.
Unlike most other studies, the present research examined performance in both the maximal and a longer steady state exercise setting. Except for Berry et al1 and Gnehm et al,8 who measured response to position in trained subjects at high prolonged intensities, previous research compared the response between positions during brief incremental exercise protocols. Ventilation changes may only become apparent after prolonged exhaustive exercise.1 Body position may therefore only influence physiological variables after a longer period of cycling. Although Berry et al1 found no significant differences between positions during longer duration exercise, Gnehm et al8 observed a significant disadvantage to the aero position during prolonged exercise.
Studies of body position in cycling must attend closely to the experimental position adopted by the participants. Biomechanical efficiency is important when cycling, and a strength of this study is the standardised position assumed by the participants. Too4 suggests that, during cycle ergometry, changing to the aero position can affect the “joint angles, muscle lengths, the muscle arm lengths thus affecting the tension-length, force velocity-power relationship . . . and (therefore) the effectiveness of force production” (286). Both Too4 and Heil et al11 argued that in previous studies, hip angle, a difficult measurement, was not adequately controlled for and therefore not a “true aero position”. In a full forward aero position, where the trunk is parallel to the thighs, the quadriceps may be placed at a disadvantage because of excessive shortening. In the length/tension relation the force obtained may decline at extreme ranges of the muscle. The mechanical advantage/disadvantage is related to how far forward the cyclist is. Jeukendrup and Martin12 state that the aero position may imp