The Method but Not the Protocol Affects Lactate-Threshold Determination in Competitive Swimmers.

PURPOSE

The study validated variables corresponding to lactate threshold (LT) in swimming. Speed (sLT), blood lactate concentration (BLLT), oxygen uptake (VO2LT), and heart rate (HRLT) corresponding to LT were calculated by 2 different incremental protocols and validated in comparison with maximal lactate steady state (MLSS).

METHODS

Ten competitive swimmers performed a 7 × 200-m front-crawl incremental "step test" with 2 protocols: (1) with 30-second rests between repetitions (short-rest incremental protocols) and (2) on a 5-minute cycle (swim + rest time, long-rest incremental protocols). Five methods were used for the assessment of sLT and corresponding BLLT, VO2LT, and HRLT: intersection of 2 lines, Dmax, modified Dmax, visual inspection, and intersection of combined linear and exponential regression lines. Subsequently, swimmers performed two to three 30-minute continuous efforts to identify speed (sMLSS) and physiological parameters corresponding to MLSS.

RESULTS

Both protocols resulted in similar sLT and corresponding physiological variables (P > .05). Bland-Altman plots showed agreement between protocols (sLT, bias: -0.017 [0.002] m·s-1; BLLT, bias: 0.0 [0.5] mmol·L-1; VO2LT, bias: -0.1 [2.2] mL·kg-1·min-1; HRLT. bias: -2 [8] beats·min-1). However, sLT calculated by modified Dmax using short rest was higher compared with speed at MLSS (1.346 [0.076] vs 1.300 [0.101] m·s-1; P < .05).

CONCLUSIONS

Calculated sLT, BLLT, VO2LT, and HRLT using all other methods in short-rest and long-rest incremental protocols were no different compared with MLSS (P > .05). Both 7 × 200-m protocols are valid for determination of sLT and corresponding physiological parameters, but the modified Dmax method may overestimate sLT.