Physiological Responses of Continuous and Intermittent Swimming at Critical Speed and Maximum Lactate Steady State in Children and Adolescent Swimmers

Abstract

Background: The purpose of this study was to compare physiological responses during continuous and intermittent swimming at intensity corresponding to critical speed (CS: slope of the distance vs. time relationship using 200 and 400-m tests) with maximal lactate steady state (MLSS) in children and adolescents.

Methods: CS and the speed corresponding to MLSS (sMLSS) were calculated in ten male children (11.5 ± 0.4 years) and ten adolescents (15.8 ± 0.7 years). Blood lactate concentration (BL), oxygen uptake ( V · O₂), and heart rate (HR) at sMLSS were compared to intermittent (10 × 200-m) and continuous swimming corresponding to CS.

Results: CS was similar to sMLSS in children (1.092 ± 0.071 vs. 1.083 ± 0.065 m·s^-1; p = 0.12) and adolescents (1.315 ± 0.068 vs. 1.297 ± 0.056 m·s^-1; p = 0.12). However, not all swimmers were able to complete 30 min at CS and BL was higher at the end of continuous swimming at CS compared to sMLSS (children: CS: 4.0 ± 1.8, sMLSS: 3.4 ± 1.5; adolescents: CS: 4.5 ± 2.3, sMLSS: 3.1 ± 0.8 mmol·L^-1; p < 0.05). V · O₂ and HR in continuous swimming at CS were not different compared to sMLSS (p > 0.05). BL, V · O₂ and HR in 10 × 200-m were similar to sMLSS and no different between groups.

Conclusion: Intermittent swimming at CS presents physiological responses similar to sMLSS. Metabolic responses of continuous swimming at CS may not correspond to MLSS in some children and adolescent swimmers.

Keywords: aerobic endurance; continuous swimming; exercise intensity domains; intermittent swimming.

Figure 1

Blood lactate concentration at the start and after the end of continuous swimming at critical speed (CS) and speed corresponding to maximum lactate steady state (sMLSS) in children (black-filled dot and square) and adolescents (white filled dot and square). *: p < 0.05, CS compared to sMLSS in both groups.

Figure 2

Blood Lactate concentration at start, min 10 and at the end of continuous effort at speed corresponding to critical speed in children ((A), filled bullets) and adolescents ((B), open bullets).

Figure 3

Blood lactate concentration during intermittent swimming (10 × 200-m) at speed corresponding to critical speed in children (filled black bullet) and adolescents (open bullet). *: p < 0.05 compared to start in children group only.

Figure 4

Oxygen uptake during intermittent swimming (10 × 200-m) at speed corresponding to critical speed in children (black-filled bullet) and adolescents (open bullets). *: p < 0.05 compared to first and second repetition in children group only. The horizontal dotted and continuous lines show the $\stackrel{·}{\mathrm{V}}$O₂ peak values of children and adolescents, respectively.