Effect of disparities of feedback on pacing in cycle time trials

The purpose of this study is to understand the effect of hypoxia during warm-up and competition on performance during cycle time trials. Methods: Seven well-trained subjects performed a VO2max test, two habituation trials, and four randomly ordered, single-blind 5 km time trials. Subjects performed HH (hypoxic WU/hypoxic TT), HN (hypoxic WU/normoxic TT), NH (normoxic WU/hypoxic TT), or NN (normoxic WU/hypoxic TT) with hypoxia (FiO2 =0.15) and normoxia (FiO2=0.21). Results: The hypoxic warm-up elicited a significant (p<.05) decrease in SaO2 (hypoxic SaO2=86%, normoxic SaO2=97%) and increases in RPE and HLa. During the TT significant differences in PO between hypoxic and normoxic TT began at 2.0 km, continuing for the duration of performance (NN PO @ 1,2,3,4,5 km=271, 271, 260, 256, 304W. NH PO=251, 239, 219, 212, 247W. HN PO=259, 258, 257, 250, 294. HH PO=238, 215, 212, 205, 245). There was no significant difference in initial PO. Discussion: Despite manipulating the pre-exercise template, PO is not reduced until afferent physiological feedback occurs within the time trial, ~2.0 km. Apparently, with changes in FiO2 subjects cannot distinguish this change, even if a low FiO2 is presented during warm-up, until physiological feedback mechanisms have time to act during the time trial