The present study investigated β-alanine ergogenic potential applied on a “real life” and training/competitive environment in swimming [4, 7, 17] and the energy provision during 400-m with this supplementation. The main findings were that β-alanine supplementation doesn’t result in metabolic contribution changes and it was ineffective in improving swimming performance.
No potential effect of β-alanine supplementation on force parameters or performance were observed. It is important to emphasize that few studies analyzed only β-alanine on competitive swimmers [4, 7]. A study involving water polo evidenced that although β-alanine results in increased force associated with peak oxygen uptake (V̇O2PEAK), this improvement does not result in improved swimming performance or metabolic changes . Evidencing the association between VO2 and increased strength in water sports , it is important to note that, in the present study, the training period coincided with a reduction in VO2max of both groups of swimmers (Table 1). Although the “classic” approach indicates a difference between the pre and post moments (Table 2; p: 0.045), a possible effect was not detected (Table 3; BFincl: 1.563), indicating that in this study this interaction may not exist.
Among the main findings of the present study, a likely reduction in ∆[La−] was found (Table 1), corroborating with some studies in different situations [6, 18]. However, this study showed very strong evidence that the reduction in ∆[La−] was a training effect (Table 3). Although most of the subjects who presented changes in this parameter were in the group that supplemented with β-alanine (Table 4), there was no effect by supplementation. Despite the reduction in ∆[La−] being a possible evidence of improved buffering, this change was not able to change 400 m performance. Based on the significant increase found for the alactic anaerobic contribution (Table 1), it is possible that, although a probabilistic effect was not evidenced (Table 3), this situation in addition to the reduction in ∆[La−] contemplates an improvement in the tolerance of shorter efforts, explaining the improvement in the fatigue index performed in 30s of tethered swimming.
Another relevant finding is regarding the alteration of different anaerobic parameters (Table 1). The decrease in Δ [La−] for both groups, may have influenced the decrease of AnLa percentile and increase the AnAl percentile, since the calculation responsible for quantifying this parameter involves lactatemia kinetics [27, 28]. Considering that mathematical components to calculate AnAl and represent EPOCFAST, a decrease of this variable may represent a possible energy compensation from both aerobic and/or anaerobic alactic metabolism [27,28,29]. Also, important to highlight that, although there are no differences between the groups, the group that supplemented with β-alanine was more likely to shown individual changes in the metabolic parameters (Table 4).
Despite the decreases indicated by anaerobic parameters (Table 1) and the individual changes (Table 4), the present study did not find alterations on the aerobic component, suggesting a failure in the metabolic balance, since these systems should be compensated in order to represent the total expenditure discharged during such an effort [27, 29]. The method presents good reproducibility to quantify anaerobic component ; however, the strategy to estimate aerobic contribution may be inadequate [27, 29].
The method used to analyze energy contribution is useful to change paradigms related to metabolic contribution, identify better pacing strategies and estimate individual capacity to develop anaerobic performance . Thus, although this method presents some limitations, it allows athletes to perform exactly as they would in training and competition. Therefore, it allows to estimate energy contribution with a greater ecological validity, since the athlete performs an effort with a metabolic cart and a snorkel attached, and V̇O2PEAK values are underestimated due to the changes in swimming technique (without turns, mechanical variations, etc.).
The absence of significant changes in swimming performance (i.e. β-alanine and PLA groups), best evidenced in the percentage of individual differences (Table 4), can be attributed to the training phase in which the tests were performed. During this training period, the total volume of training was distributed in a way that ~ 70% of the training sessions were performed with swimming, considered by the swimmers of easy intensity (i.e., blood lactate < 2 mM), and ~ 30% in high intensity (blood lactate > 4 mM). Hence, the supplementation period was carried out during specific training periods. No measurements were conducted after taper.
β-alanine supplementation has been used in various sports, such as swimming [4, 7, 17], running [9, 33], cycling , resistance training [34, 35], water polo [6, 18] and repeated sprint ability . The dosages vary among the studies available in the literature, with fixed quantities (1.6 g up to 6.4 g∙day− 1) and body mass (0.3 g∙kg− 1) [9, 33, 34]. Therefore, β-alanine’s function is to avoid intramuscular pH variations and is commonly combined with others ergogenic substances (buffer or stimulation) such as creatine,  or sodium bicarbonate (SB) [7, 33].
De Salles Painelli et al. (2013) investigated the effects of two supplementation strategies (β-alanine alone and in combination with SB) on 100-m and 200-m swimming performance. In β-alanine alone, sixteen swimmers received 3.2 g·day− 1 for 1 week and 6.4 g·day− 1 for 4 weeks and combining with SB (0.3 g∙kg− 1) on the last day of tests. Their main findings were that β-alanine supplementation, β-alanine supplementation with SB addition to the effort and only SB addition to effort effectively similarly improved 200-m freestyle performance, and tended to improve 100-m performance .
The β-alanine supplementation dose and time of exposure on the study performed by Salles Painelli et al. (2013) were similar to our study; however, the authors found no significant differences in buffer capacity (fatigue index) or ergogenic aid (peak and mean force, impulse and performance) were found . This can be attributed to the metabolic characteristics of 400-m effort, around 80% of total energy demand is from of the aerobic system [1, 36], in comparison with the findings by Figueiredo et al. (2011), who reported a metabolic contribution of 65.9% Aer, 13.6% AnLa, and 20.4% AnAl during 200-m performance.
Mero et al. (2013) investigated the effects of a six-week supplementation using only β-alanine (4.8 g·day− 1) or PLA and combined co-administration of SB or PLA before two 100-m maximum freestyle bouts. Although pH increase was observed in both groups with SB, performance improvement was only observed when compared with PLA alone, and no differences were found for blood lactate concentration, evidencing that β-alanine supplementation did not provide significant alterations and effects were recurrent from SB administration. Under similar conditions of supplementation (time and quantity), the authors reported no alterations in performance, corroborating the present study. However, it should be noted that no changes in blood lactate concentration can be linked to the effort’s duration . In addition, the non-parametric statistics used by Mero et al. (2013) may have limited the results of their analysis.
Nevertheless, a recent review  showed that β-alanine supplementation could have some influence in exercises lasting from 30s to 10 min. The 400-m performance in the present study was around 290 s, slightly longer than 4 min, and two studies [7, 17] on 100-m performance, where time was slightly shorter than 60 s, reported no significant effects of β-alanine supplementation. However, during a 200-m maximum effort, De Salles Painelli et al. (2013) observed significant improvement.
Chung et al. (2012) administrated 4.8 g·day− 1 of β-alanine for 4 weeks, following 6 weeks of 3.2 g·day− 1 or placebo, totalizing 10 weeks. Performances were assessed in important competitions, National Championships and international or national selection meet, and supplementation was conducted between them. The authors concluded that 10 weeks of β-alanine supplementation was not capable of improving physiological or performance benefits in a non-laboratory controlled, real-world competition, in elite/sub-elite swimmers.
Finally, although several studies have demonstrated that β-alanine supplementation can improve high intensity exercise performance [3, 4, 17], De Salles Painelli et al. (2013) stated that fewer studies have examined the effects on competitive performance. In the attempt to fill this gap, the present study demonstrated that β-alanine was not effective in increasing performance in 400-m. Nevertheless, new investigations are needed to determine which sports could benefit from the ergogenic effect of β-alanine (performance and training quality in speed and acidosis tolerance sets, 800-m running, team and combat sports).
The present study has some limitations, only three studies had their focus on swimming performance analysis, and none has quantified the metabolic contribution on β-alanine supplementation to make comparisons with the same method of quantification and modality. Therefore, this is the first study focused on shortening this gap in the literature. Even from the evidence of Stegen et al. (2013) the lack of intramuscular carnosine content measurement can be considered a limitation. Despite not measuring intramuscular carnosine, Harris et al. (2006) evidenced that the dose used in the present study seems sufficient to increase intramuscular content of carnosine even in a short period of supplementation. The chosen dose of β-alanine caused paresthesia on three athletes, showing which group was PLA and which was β-alanine. Finally, there were no nutritional control during supplementation, as feeding may influence the amount of carnosine originated by β-alanine supplementation.
Despite the methodologic constraints inherent in studies involving competitive athletes (e.g., reduced sample size, competition schedule, inability to perform invasive methodologies), they are important to substantiate the efficiency of nutritional aids over performance and metabolic contribution in sports.