The effect of the aerodynamic time-trial position on gross efficiency and self-paced time-trial performance

Abstract

To investigate the physiological and metabolic effects of different torso angles (TA; while systematically controlling the aerodynamic time-trial position; AP), during submaximal exercise and self-paced time-trial efforts. Twelve participants completed four visits to the laboratory: Visit 1 being an incremental exercise test to identify power at maximal pulmonary oxygen uptake (PV?O_2max) and Visits 2 to 4 being 20-minute time-trials with pre and post gross efficiency (GE) tests, performed at three different TAs (0^o, 12^o, 24^o). GE was significantly reduced at the 0^o TA, when compared to the 24^o TA (P = 0.039). GE was significantly lower after the time-trials when compared to Pre GE (P < 0.001). There was no significant difference in the magnitude of decline in GE between TA. Combined data from all TA revealed a significant positive correlation between GE and mean time-trial power output (PO; R = 0.337; R² = 0.114; P = 0.044). Mean time-trial PO was significantly higher at the 24^o TA, when compared to the 12^o TA (P = 0.012) and 0^o TA (P = 0.007). There was a significant positive correlation between relative TA and mean time-trial PO (R = 0.374; R² = 0.140; P = 0.025). GE declines during time-trial exercise, while lower TAs do not further exacerbate the magnitude of decline in GE. Lowering TA results in a reduction in physiological and metabolic performance at submaximal and time-trial intensity. There remains a trade-off between physiological functioning and aerodynamic drag.