Estimating Lactate Threshold Power From The End Power Of A 3-min All-out Cycling Test

Abstract

The average power output over the last 30 s of a 3-min all-out cycling test (end power, EP) has been shown to be equivalent to critical power, a power sustainable for approximately 30 min. By comparing EP to the power at established measures of blood lactate concentration ([BLa]), the 3-min all-out cycling test (3MT) could be used in place of a lactate threshold (LT) test in certain applications. PURPOSE: The primary aim of this study was to compare power at LT to EP. A secondary aim was to provide the methodology to perform the 3MT using equipment readily available to cyclists. METHODS: Eight competitive cyclists (7 men, 1 woman, age = 35 ± 7 yrs, VO2peak = 64 ± 7 mL·kg-1·min-1) completed 3 laboratory visits within a 14 d period, each visit separated by at least 48 h. All tests were performed using the subjects‘ own bicycles and a laboratory provided rear wheel with a power measuring hub (WHEEL). Visit 1: The subjects performed an incremental load test (100 W initial load increasing stepwise 25 W every 4 min) to volitional termination using an electronically controlled load. Blood samples were taken during minute 3 of each 4 min stage, and immediately analyzed for [BLa]. VO2peak was established as the highest 20 s average VO2 observed. [BLa] versus power was fit to a third order polynomial curve and 3 measures of power at LT were mathematically determined: power at an absolute [BLa] of 4 mmol·L-1 (P-OBLA); power at a [BLa] of 1 mmol·L-1 over exercise baseline (P-1E); and power at the second of 2 subsequent ≥ 1 mmol·L-1 increases in [BLa] (P-1+1). Visits 2 and 3: Subjects performed the 3MT using a progressive resistance trainer, and were instructed to give maximal effort throughout the test. A familiarization trial for the 3MT was performed on Visit 2. During Visit 3, the EP was recorded as the mean power over the last 30 s of the 3MT. RESULTS: Repeated measures ANOVA showed EP (278 ± 47 W) was significantly greater (P < 0.05) than P-OBLA (239 ± 55 W), P-1E (209 ± 48 W), and P-1+1 (216 ± 60 W). Pearson correlation showed EP was correlated with P-OBLA (r = 0.82, P = 0.007), P-1E (r = 0.79, P = 0.010), and P-1+1 (r = 0.86, P = 0.003). Using linear regression, P-OBLA could be estimated at 86% EP, P-1E at 75% EP, and P-1+1 at 78% EP. CONCLUSION: The EP from the 3MT can be used to estimate power at LT in competitive cyclists, using readily available equipment.