Comparison Of A Field Based Test To Estimate Functional Threshold Power And Power Output At Lactate Threshold

Abstract

It has been proposed that field based tests used to estimate functional threshold power (FTP) result in a power output equivalent to power output at lactate threshold (LT). However, anecdotal evidence from regional cycling teams tested for lactate threshold in our laboratory suggested that power output at lactate threshold underestimated FTP. PURPOSE: It was hypothesized that estimated FTP is not equivalent to power output at lactate threshold. METHODS: In trained cyclists, FTP was estimated from an 8-min field test and compared to power output at LT using two methods; LTdelta1, a 1 mmol/L or greater rise in blood lactate in response to an increase in workload and LT4.0, blood lactate of 4.0 mmol/L. RESULTS: Estimated FTP was equivalent to power output at LT4.0 and greater than power output at LTdelta1. Maximal oxygen consumption (VO2max) explained 93% of the variance in individual power outputs during the 8-min field test. When 8-min field test power output was expressed relative to maximal power output from the VO2max test (individual exercise performance), VO2max explained 64% of the variance in individual exercise performance. Power output at LT was not related to 8-min field test power output. CONCLUSIONS: In trained cyclists, FTP estimated from an 8-min field test is equivalent to power output at lactate threshold if LT4.0 is used, but is not equivalent for all methods of lactate threshold determination including LTdelta1.