Cardiorespiratory responses to seat-tube angle variation during steady-state cycling.

The effect of seat-tube angle (STA) variation on oxygen consumption (VO2), heart rate (HR), ventilation (VE), and rating of perceived exertion (RPE) on 25 trained competitive triathletes and cyclists was evaluated during 10-min submaximal tests at each of four STAs (69 degrees, 76 degrees, 83 degrees, 90 degrees). Subjects averaged (mean +/- SD) 26.5 +/- 6.4 yr of age, 68.5 +/- 9.8 kg, 4.26 +/- 0.58 l.min-1 for VO2peak, and 76.2 +/- 1.5 degrees for preferred STA. Tests occurred on a modified cycle ergometer (at each subject's preferred dimensions, except for STA) at a power output that averaged 73% of the subjects' VO2peak and pedaling 90 rpm while using aerodynamic handlebars. Mean VO2, HR, and RPE values at 83 degrees and 90 degrees were significantly lower than values at 69 degrees (3.09, 3.10 vs 3.17 l.min-1; 149.6, 149.9 vs 152.9 bpm; 13.5, 13.5 vs 14.2, respectively; P < 0.05). VE at 83 degrees was significantly lower than VE at 69 degrees (65.2 vs 68.2 l.min-1; P = 0.011). A kinematic analysis found greater hip extension, ankle plantar flexion, and a lower-limb orientation more directly over the crank axis when STA increased. Therefore, only the 69 degrees STA appeared to be a detriment to steady-state cardiorespiratory responses during cycling, whereas the 76 degrees, 83 degrees, and 90 degrees STAs elicited similar cardio-respiratory responses.