Abstract
Maximal Lactate Steady State (MLSS) and Lactate Threshold (LT) are physiologically-related and fundamental concepts within the sports and exercise sciences. Literature supporting their relationship, however, is scarce. Among the recognized LTs, we were particularly interested in the disused "Minimum Lactate Equivalent" (LE(min)), first described in the early 1980s. We hypothesized that velocity at LT, conceptually comprehended as in the old days (LE(min)), could predict velocity at MLSS ((V)MLSS) more accurate than some other blood lactate-related thresholds (BL(R)Ts) routinely used nowadays by many sport science practitioners. Thirteen male endurance-trained [(V)MLSS 15.0 ± 1.1 km·h(-1); maximal oxygen uptake ( V.O2max ) 67.6 ± 4.1 ml·kg(-1)·min(-1)] homogeneous (coefficient of variation: ≈7%) runners conducted 1) a submaximal discontinuous incremental running test to determine several BL(R)Ts followed by a maximal ramp incremental running test for V.O2max determination, and 2) several (4-5) constant velocity running tests to determine (V)MLSS with a precision of 0.20 km·h(-1). Determined BL(R)Ts include LE(min) and LE(min)-related LE(min) plus 1 (LE(min+1mM)) and 1.5 mmol·L(-1) (LE(min+1.5mM)), along with well-established BL(R)Ts such as conventionally-calculated LT, D(max) and fixed blood lactate concentration thresholds. LE(min) did not differ from LT (P = 0.71; ES: 0.08) and was 27% lower than MLSS (P < 0.001; ES: 3.54). LE(min+1mM) was not different from MLSS (P = 0.47; ES: 0.09). LE(min) was the best predictor of (V)MLSS (r = 0.91; P < 0.001; SEE = 0.47 km·h(-1)), followed by LE(min+1mM) (r = 0.86; P < 0.001; SEE = 0.58 km·h(-1)) and LE(min+1.5mM) (r = 0.84; P < 0.001; SEE = 0.86 km·h(-1)). There was no statistical difference between MLSS and estimated MLSS using LE(min) prediction formula (P = 0.99; ES: 0.001). Mean bias and limits of agreement were 0.00 ± 0.45 km·h(-1) and ±0.89 km·h(-1). Additionally, LE(min), LE(min+1mM) and LE(min+1.5mM) were the best predictors of V.O2max (r = 0.72-0.79; P < 0.001). These results support LE(min), an objective submaximal overlooked and underused BL(R)T, to be one of the best single MLSS predictors in endurance trained runners. Our study advocates factors controlling LE(min) to be shared, at least partly, with those controlling MLSS.