Lactate thresholds are commonly used as estimates of the highest workload where lactate production and elimination are in equilibrium (maximum lactate steady state [MLSS]). However, because of the high static load on propulsive muscles, lactate kinetics in inline speed skating may differ significantly from other endurance exercise modes. Therefore, the discipline-specific validity of lactate thresholds has to be verified. Sixteen competitive inline-speed skaters (age: 30 ± 10 years; training per week: 10 ± 4 hours) completed an exhaustive stepwise incremental exercise test (start 24 km/h, step duration 3 minutes, increment 2 km/h) to determine individual anaerobic threshold (IAT) and the workload corresponding to a blood lactate concentration of 4 mmol/L (LT4) and 2-5 continuous load tests of (up to) 30 minutes to determine MLSS. The IAT and LT4 correlated significantly with MLSS, and the mean differences were almost negligible (MLSS 29.5 ± 2.5 km/h; IAT 29.2 ± 2.0 km/h; LT4 29.6 ± 2.3 km/h; p > 0.1 for all differences). However, the variability of differences was considerable resulting in 95% limits of agreement in the upper range of values known from other endurance disciplines (2.6 km/h [8.8%] for IAT and 3.1 km/h [10.3%] for LT4). Consequently, IAT and LT4 may be considered as valid estimates of the MLSS in inline speed skating, but verification by means of a constant load test should be considered in cases of doubt or when optimal accuracy is needed (e.g., in elite athletes or scientific studies).
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