Oxygen uptake kinetics and energy system's contribution around maximal lactate steady state swimming intensity.

Jailton Gregório Pelarigo,João Paulo Vilas-Boas,Leandro Machado,Camila Coelho Greco,Ricardo Jorge Fernandes,Juan Sastre

doi:10.1371/journal.pone.0167263

Abstract

The purpose of this study was to examine the oxygen uptake () kinetics and the energy systems’ contribution at 97.5, 100 and 102.5% of the maximal lactate steady state (MLSS) swimming intensity. Ten elite female swimmers performed three-to-five 30 min submaximal constant swimming bouts at imposed paces for the determination of the swimming velocity (v) at 100%MLSS based on a 7 x 200 m intermittent incremental protocol until voluntary exhaustion to find the v associated at the individual anaerobic threshold. kinetics (cardiodynamic, primary and slow component phases) and the aerobic and anaerobic energy contributions were assessed during the continuous exercises, which the former was studied for the beginning and second phase of exercise. Subjects showed similar time delay (TD) (mean = 11.5–14.3 s) and time constant (τp) (mean = 13.8–16.3 s) as a function of v, but reduced amplitude of the primary component for 97.5% (35.7 ± 7.3 mL.kg.min-1) compared to 100 and 102.5%MLSS (41.0 ± 7.0 and 41.3 ± 5.4 mL.kg.min-1, respectively), and τp decreased (mean = 9.6–10.8 s) during the second phase of exercise. Despite the slow component did not occur for all swimmers at all swim intensities, when observed it tended to increase as a function of v. Moreover, the total energy contribution was almost exclusively aerobic (98–99%) at 97.5, 100 and 102.5%MLSS. We suggest that well-trained endurance swimmers with a fast TD and τp values may be able to adjust faster the physiological requirements to minimize the amplitude of the slow component appearance, parameter associated with the fatigue delay and increase in exhaustion time during performance, however, these fast adjustments were not able to control the progressive fatigue occurred slightly above MLSS, and most of swimmers reached exhaustion before 30min swam.

Highlights

An important aspect of aerobic endurance performance is the ability to sustain the highest percentage of maximal oxygen uptake (%V_ O2max) as long as possible
All swimmers performed 30 min when swimming at 97.5 and 100%maximal lactate steady state (MLSS), but eight swimmers were not able to maintain the predetermined v during 30 min at 102.5%MLSS, reaching voluntary exhaustion at 19.3 ± 4.9 min
0.633, respectively) (Table 1). [La-] and Heart rate (HR) values for the three swim intensities are shown in Table 1 with a higher values at 102.5%MLSS compared to 97.5 and 100%MLSS for [La-]

Summary

Introduction

An important aspect of aerobic endurance performance is the ability to sustain the highest percentage of maximal oxygen uptake (%V_ O2max) as long as possible. In this sense, coaches and swimmers have used the %V_ O2max in different submaximal intensities to control, prescribe and improve sports training [1]. The moderate domain is described as the exercise intensities in which a state steady for V_ O2 is achieved within 3 min of constant exercise [5]. The heavy domain is described as the exercise intensities in which V_ O2 slow component should be evident, causing a delay on the achievement of the V_ O2 steady-state during exercise [2]. The severe domain is described as the exercise intensities in which V_ O2 is elevated compared to rest values and continue to increase over time, leading to attain the V_ O2max [6, 7]

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