Blood Lactate and Cardiovascular Responses to Upright or Aerodynamic Positions on a Cycle Ergometer

Abstract

PURPOSE: The purpose of this study was to examine the cardiovascular and blood lactate responses to exercise during an incremental step test when adopting a conventional upright posture (UP) compared to an aerodynamic posture (AP) and the implications for identifying lactate and heart rate transitions. METHODS: Following Institutional ethics approval n=5 well-trained male cyclists agreed to participate (age, 30.5 ± 6.0 yrs; height, 174.0 ± 8.0 cm; mass, 71.0 ± 5.0 kg; VO2max 57.4 ± 7.0 ml.kg-1.min-1). Each participant completed 4 step tests, of which 2 were (UP) and 2 (AP) in a randomised order. For UP trials the participant rode with their hands on the top of the handlebars while for AP the ergometer was fitted with aerodynamic time-trial handlebars. All trials were completed on an electronically controlled cycle ergometer with cadence held constant at 90 rpm and work rate increasing by 25 W.3min-1 from an initial workload of 100 W. For all trials cardiovascular responses were determined through thoracic impedance monitoring where Q = HR x SVi x BSA (SVi = stroke volume index and BSA = body surface area) and HR was determined by the R-R interval. Blood lactate was collected upon completion of each workload. Lactate threshold (LT1) determined as the initial rise in BLa and lactate turn-point (LT2) as the rapid rise in BLa. RESULTS: There were significant differences for SV (UP 109.3 ± 5.7 ml; AP 104.4 ± 1.7 ml) (P= 0.000) and HR (UP 133.9 ± 23.9; AP 137.3 ± 25.1 b.min-1) (P= 0.0001) when comparing responses across all workloads, however no-significant differences were observed when comparing UP to AP for each workload (p> 0.05). Significant differences (p< 0.05) highlighted for BLa at 225 W (UP: 2.3 ± 0.6 mM) (AP: 2.5 ± 0.6 mM); 250 W (3.2 ± 1.2) (AP: 3.7 ± 1.1 mM); 275 W (UP: 4.5 ± 1.8 mM) (AP: 5.6 ± 1.9 mM) and 300 W (UP: 5.1 ± 2.0 mM) (AP: 7.2 ± 2.9 mM). LT1 in UP (165 ± 22.3 W) was significantly different to AP (135 13.6 W) (P= 0.001) with LT2 in UP, 270 ± 32.5 W being significantly different to LT2 AP, 245 ± 20.9 W (P= 0.01). CONCLUSIONS: These data suggest that the posture adopted by the rider during an incremental step test for determination of BLa and cardiovascular responses can have a profound response. Caution needs to be applied when conducting such tests to ensure that the posture reflects the conditions the rider will be using when training and competing.