Limitations Of Incremental Tests In Performance Testing (pr)

Limitations of incremental tests in performance testing – unstable lactate and oxygen kinetics at higher workloads P Reynolds, B Donne Deparment of Physiology, Trinity College Dublin Introduction: Incremental exercise tests are considered the ‘gold standard’ for performance evaluation and estimation of lactate threshold (LT). Their accuracy relies on the assumption of steady O2 and lactate kinetics at the end of each workload segment. Both oxygen uptake (ܸሶ O2) and blood lactate concentration (BLa) show increases over time above theoretical ‘threshold’ 1,2 questioning the validity of this assumption . This study sought to assess the effects of the time dependent component of ܸሶ O2 and BLa on each other. Methods: Nine male cyclists participated in this study. Cyclists were medically cleared prior to participation and performed a graded incremental test to volitional exhaustion to determine maximum power (Pmax) and LT. Their HR, ܸሶ O2 and BLa were recorded at regular intervals. Subsequently on separate days four 30 minute steady state tests were performed at workloads equivalent to 90%LT, LT, LT+25%δ and LT+50%δ where (δ=Pmax-LT). Rates of increase of BLa (dBLa/dt) and ܸሶ O2 (dܸሶ O2/dt) were computed. Results: 1F-RM Anova detected significantly larger mean dBLa/dt and dܸሶ O2/dt in the LT+50% -1 -1 -1 -2 protocol only; 0.393±0.085mmol.L .min and 0.5±0.11mL.kg .min respectively (P<0.01). Significant correlation was detected between mean dBLa/dt and mean dܸሶ O2/dt for test LT+50%δ (r=0.81). 2F-RM Anova performed on data from 90%LT, LT and LT+25%δ tests detected significant interaction of time and exercise intensity on dBLa/dt throughout each test and on dܸሶ O2/dt during the first 6min. Occurrence of max dBLa/dt and max dܸሶ O2/dt were typically more than 3min apart. Discussion: These results demonstrated that dBLa/dt at a particular exercise intensity is time dependent and that dBLa/dt at a particular time is exercise intensity dependent. This, together with the fact that there was a significant time delay between a recorded oxygen deficit and an increase in BLa, would suggest that further investigation be done into the appropriate duration of each exercise segment during incremental tests. The results of this study would also support the addition of repeated steady state tests to conventional incremental testing to improve accuracy of estimations involving BLa. 1: Whipp BJ & Wasserman K (1972). Oxygen uptake for various intensities of constant-load exercise. J Appl Physiol 33, 351–356. 2: Beneke R. (2003). Methodological aspects of maximal lactate steady state - implications for performance testing. Eur J App Physiol 89, 95-99