EFFECT OF CYCLING POSITION ON VENTILATORY AND METABOLIC VARIABLES

Three positions are generally used by cyclists: upright posture (UP), dropped posture (DP) and aero posture (AP). They determine different a ngles of trunk flexion which could be associated with physiological ch anges. The purpose of this study was to analyse the effect of these ri der positions on ventilatory and metabolic variables. Nine male compet itive cyclists (26.3 +/- 3 yrs, mean +/- SD) exercised on a cycle ergo meter. Subjects performed three 10 min exercise bouts at 70% (V) over dot O(2)max (maximal oxygen uptake, l.min(-1)) in UP, DP and AP, in a randomized order. Each bout was separated by a 5 min active recovery p eriod (50% of (V) over dot O(2)max). Ventilatory and gas exchange resp onses to exercise were averaged every min. Blood lactate concentration ([La](b), mM), blood pH were analysed at the 5th and the 10th min. Th e ventilation, respiratory exchange ratio, mean inspiratory flow, [La] (b) and perceived exertion were significantly higher in DP (88.4 +/- 1 1.4 l.min(-1), 0.96 +/- 0.05 ml.s(-1), 2.52 +/- 0.84 Mm and 13.6 +/- 1 .2) than in UP (84.8 +/- 12.3 l.min(-1), 0.94 +/- 0.05 ml.s(-1). 2.14 +/- 0.99 Mm and 12.1 +/- 1.5). (V) over dot O-2, tidal volume, carbon dioxide output, respiratory rate, inspiratory duty cycle, heart rate a nd pH remained unchanged between all riding positions (averaged values for the three positions: 3.09 +/- 0.006 l.min(-1), 2.34 +/- 0.006 l.b r(-1), 3.01 +/- 0.04 l.min(-1), 37.4 +/- 0.8 br.min(-1), 0.47 +/- 0, 1 62 +/- 1 beat.min(-1) and 7.38 +/- 0.015). These results showed that t he greater changes in ventilatory and metabolic variables occurred in DP. AP appears to be the more suitable position when the aerodynamic d rag becomes predominant.