Forty non-vegetarian, non-smoking, well-trained, experienced judo (n = 19) and jiu-jitsu (n = 21) male competitors volunteered to participate in the study. Three participants dropped out the study after the initial tests due to personal reasons not directly related to the study, so that a total of 37 athletes (judo: n = 16, jiu-jitsu: n = 21) completed the entire protocol. Participants’ characteristics are presented in Table 1. Six participants were International level athletes and a further seven were competing at National level. The remaining 24 athletes were actively participating in state-level official competitions at the time of data collection. Participants were not taking creatine or BA for 3 and 6 months prior to the study, respectively. All of the participants were fully informed of the risks and discomforts associated with the study before giving their written informed consent. The study was approved by the institution’s Ethical Advisory Committee.
A randomized, double-blind, placebo-controlled, parallel-group study was conducted. Each athlete was assigned to one of the four groups: Placebo+Placebo (PL+PL, n = 09); Beta-alanine+Placebo (BA+PL, n = 10); Placebo+Sodium Bicarbonate (PL+SB, n = 09) or Beta-alanine+Sodium Bicarbonate (BA+SB, n = 09). In contrast to previous studies that used a parallel-group design to assess of BA supplementation, coupled with a cross-over design to assess the effects of the co-ingestion of BA and SB, we adopted a full parallel-group design.
All athletes were submitted to the same experimental procedures on two different occasions, 4 weeks apart. The trials were completed before (PRE) and after (POST) 4 weeks of supplementation. In each trial, athletes’ performance was assessed using a 4-bout 30-s upper-body Wingate Test with a 3-min recovery period between each bout.
Blood samples were collected at rest, immediately and 5 min after the fourth bout of the Wingate test. Ratings of perceived exertion were also collected immediately after the fourth bout, using a 6–20 Borg scale (Borg 1982). To avoid the influence of diet on performance, athletes filled-out a 24-h food diary on the day preceding the first trial and were instructed to repeat the same diet on the day preceding the second trial. The volunteers were also instructed to arrive well fed and hydrated, but without having ingested any food for 3 h prior to the test. The athletes were also asked to abstain from intense exercise, alcohol and caffeine on the day preceding each test. Compliance with these requests was confirmed verbally with each participant prior to them commencing each trial. The experimental design of this study is illustrated in Fig. 1.
All participants receiving BA (i.e., BA+PL and BA+SB groups) were supplemented with 6.4 g d−1 of BA (CarnoSyn™, Natural Alternatives International, San Marcos, California, USA) for 4 weeks (2 × 800 mg gelatin capsules, taken 4 times per day). The other two groups (PL+SB and PL+PL) received the same amount of dextrose (placebo) in gelatin capsules identical in appearance and number. At the beginning of the fourth week of supplementation, all athletes were required to start a chronic SB or calcium carbonate (placebo) supplementation protocol as follows: 500 mg kg−1 BM d−1 (4 × 125 mg kg−1 B Md−1) for 7 days. SB was given to the PL+SB and BA+SB groups, whilst calcium carbonate was given to the BA+PL and PL+PL groups. Both substances were provided in gelatin capsules of identical number and appearance. Supplementation ceased on the day preceding the post-supplementation trial. The supplementation protocol is depicted in the Fig. 1.
In order to slow the absorption of BA and minimize paraesthesia, a side effect related to elevated plasma peaks of BA (Décombaz et al. 2011), carboxymethyl cellulose was added to BA capsules. Carboxymethyl cellulose was also added to the dextrose placebo capsules. Each athlete was asked to report any unusual symptoms during the first (i.e. BA or dextrose) and the second (i.e., SB or calcium carbonate) phases of the supplementation protocol. Athletes were also asked to report the substances they believed they were taking during both phases.
In order to evaluate the effect of supplementation on high-intensity intermittent exercise performance, athletes completed a 4-bout upper-body Wingate test, using a specifically designed ergometer (EB 4100, Cefise, Brazil). Each bout lasted 30 s and the load was set at 5 % of body weight, which was measured with a digital scale to the nearest 10 g. Bouts were interspersed by 3-min passive recovery periods. Athletes warmed up for 3 min on the ergometer before the first bout. A set of 24 sensors measured wheel velocity, with power output being calculated automatically every second by computer software (Ergometric 6.0, Cefise, Brazil). Mean power and peak power were obtained for each bout, and total work done was obtained for the overall test session (i.e. 4 × 30 s bouts).
Data from a pilot test–retest study revealed that this protocol is highly reproducible in athletes with similar characteristics (average variation = 0.6 %, ICC = 0.973, r = 0.942, F = 0.06, p = 0.80). A previous investigation from our group has also shown that this protocol was very sensitive to detect the ergogenic effects of acute sodium bicarbonate supplementation and that it is related to a sport-specific performance test (Artioli et al. 2007).
Blood sampling and lactate analysis
Blood samples were collected from the fingertip before, immediately after and 5 min after the fourth Wingate bout. The 25 μL samples were immediately stored in the same volume of ice-cold 2 % NaF solution. Samples were subjected to electrochemical analysis in an automated device (YSI 1500, Yellow Springs, OH, USA) within the same day of collection, and the values obtained were corrected by the dilution factor.
Rate of perceived exertion
Subjective feelings of fatigue were reported immediately after the fourth bout of the Wingate test before and after supplementation using a 6–20 Borg scale.
One-way ANOVA followed by a LSD post hoc test was used to compare the participant characteristics and baseline performance between groups. Mixed models for repeated measures followed by single-degree-of-freedom contrast analysis were used to test between- and within-group differences in mean power, peak power, total work done and blood lactate. Absolute changes (i.e. Δ POST–PRE supplementation) analyses were performed to compare total work done between the experimental groups, using a one-way ANOVA followed by LSD post hoc test. Rates of perceived exertion were compared within groups using Wilcoxon’s signed rank test with the Bonferroni adjustment. Cohen’s effect size (Cohen 1988) and magnitude-based inference analysis (Batterham and Hopkins 2006) were also calculated for total work done, the main outcome measure in this study. Fischer exact test was used to test whether there were differences between groups in the incidence of side effects and the rate of participants who correctly guessed their allocation in the trial. Data analyses were conducted using SAS package, version 9.2. Results are expressed as mean ± SD. Significance level was set at p < 0.05, with a trend towards significance being accepted at p < 0.1.