endicular to the ground. They maintained an anterior pelvic tilt and kept their trunk in the upright cycling position. In the aero position the participants assumed a crouched position, with their trunk held parallel to the ground. They were asked to maintain a posterior pelvic tilt and to allow their thoracic spine to “drop” towards their thighs. Wrists and hands rested on the aerobars. All participants were monitored and given verbal feedback to maintain the positions.
Maximal oxygen uptake
Two Vo2max tests were completed on each participant (aero and upright). Vo2 was measured with an online, indirect calorimetry system. Participants exercised on a Monark stationary bicycle. The standard Monark handlebars were modified with clip on aerobars (Bioarm, Italy) with forearm pads for the aero position. Seat height was set for each participant with 25–30° flexion in the extended leg. Seat height for each participant remained constant for the four protocols. Leg length was measured from the anterior superior iliac spine to the distal portion of the lateral malleolus.
Each participant was fitted with a nose clip and mouthpiece attached to a Hans Rudolph two way R2700 valve. This was passed through a metre of large bore tubing to a 2.6 1itre mixing chamber from which dried gas was sampled continuously. A Labview On-line computer system was used to perform the calculation of Vco2, Vo2, minute ventilation (Ve), tidal volume, and respiratory exchange ratio every 30 seconds. Heart rate was recorded continuously using a Polar Electro PE3000 Sportstester heart rate monitor (information recorded every 15 seconds).
The protocol for both maximum tests started with a five minute warm up followed by a five minute rest. The participant then began cycling at 50 W increasing to 100 W after one minute. The workload was then increased by 25 W every minute until volitional exhaustion or he reached a plateau in heart rate and/or Vo2 response. The max tests were performed on two different days at approximately the same time, one to two weeks apart.
Steady state sessions
After the participant had assumed the experimental position (aero or upright), exercise started at 50 W and continued for 45 minutes at the three absolute workloads previously outlined. Blood samples were taken every 2.5 minutes as previously described.
Venous catheters were inserted into the antecubital vein. An initial 2 ml of the catheter system contents (blood saline mixture) was discarded before withdrawal of the main 3 ml sample. Between samples, the catheter system was flushed with 12 ml heparinised saline to prevent clotting. From each main sample, 1 ml was immediately deproteinised in 2 ml ice cold 8% perchloric acid. The samples were vortex mixed and centrifuged, and the supernatant was frozen at −20°C for later enzymatic analysis of lactate.
Gross mechanical efficiency
The percentage gross mechanical efficiency (%GME) was calculated from the following equation at the final minute of each workload (steady state):
Individual mean maximal exercise data were analysed with a paired t test. The steady state exercise data were analysed using the last five minutes of each of the three levels of intensity (50, 100, 150 W). Submaximal exercise data were analysed using paired t tests and repeated measures analysis of variance. Data are reported as mean (SD).
The participants had a mean age of 19.1 (1.10) years, height of 181.95 (4.27) cm, mass of 70.98 (3.12) kg, and body mass index of 21.46 (1.21).
Table 1 summarises maximal values for participants in both aero and upright positions during one minute of incremental exercise testing. Participants had a significantly higher Vo2max (ml/kg/min), heart rate maximum, and VEmax, and achieved a greater workload in the upright position. There was no significant difference between positions for Vo2max measured in litres/min.
Steady state exercise
During submaximal work at three absolute work outputs (50, 100, 150 W), variables increased in a stepwise fashion as intensity of exercise increased (table 2). A significant difference was found b