The Maximal Lactate Steady State Workload Determines Individual Swimming Performance

The lactate threshold (LT) and the strongly related maximal lactate steady state workload (MLSS(W)) are critical for physical endurance capacity and therefore of major interest in numerous sports. However, their relevance to individual swimming performance is not well understood. We used a custom-made visual light pacer for real-time speed modulation during front crawl to determine the LT and MLSS(W) in a single-exercise test. When approaching the LT, we found that minute variations in swimming speed had considerable effects on blood lactate concentration ([La(−)]). The LT was characterized by a sudden increase in [La(−)], while the MLSS(W) occurred after a subsequent workload reduction, as indicated by a rapid cessation of blood lactate accumulation. Determination of the MLSS(W) by this so-called “individual lactate threshold” (ILT)-test was highly reproducible and valid in a constant speed test. Mean swimming speed in 800 and 1,500 m competition (S-Comp) was 3.4% above MLSS(W) level and S-Comp, and the difference between S-Comp and the MLSS(W) (Δ S-Comp/MLSS(W)) were higher for long-distance swimmers (800–1,500 m) than for short- and middle-distance swimmers (50–400 m). Moreover, Δ S-Comp/MLSS(W) varied significantly between subjects and had a strong influence on overall swimming performance. Our results demonstrate that the MLSS(W) determines individual swimming performance, reflects endurance capacity in the sub- to supra-threshold range, and is therefore appropriate to adjust training intensity in moderate to severe domains of exercise.