EFFECTS OF VARIOUS SODIUM BICARBONATE
LOADING PROTOCOLS ON THE TIME-DEPENDENT
EXTRACELLULAR BUFFERING PROFILE
J.C. SIEGLER,1 A.W. MIDGLEY,1 R.C.J. POLMAN,2
AND
R. LEVER1
1
Department of Sport, Health & Exercise Science, University of Hull, Hull, United Kingdom; and 2Centre for Applied Sport and
Exercise Sciences, University of Central Lancashire, Preston, United Kingdom
ABSTRACT
Siegler, JC, Midgley, AW, Polman, RCJ, and Lever, R. Effects of
various sodium bicarbonate loading protocols on the timedependent extracellular buffering profile. J Strength Cond Res
23(x): 000–000, 2009—Although much research has investigated the types of exercise that are enhanced with sodium
bicarbonate (NaHCO3) ingestion, to date, there has been limited
research on the dosage and timing of ingestion that optimizes the
associated ergogenic effects. This study investigated the effects
of various NaHCO3 loading protocols on the time-dependent
blood–buffering profile. Eight male volunteers (age, 22.4 6 5.7
yr; height, 179.8 6 9.6 cm, body mass, 76.3 6 14.1 kg)
completed Part A, measures of alkalosis throughout 120 minutes
after ingestion of various single NaHCO3 dosages (0.3 gkg21,
0.2 gkg21, 0.1 gkg21, and placebo); and Part B, similar profiles
after alternative NaHCO3 loading protocols (single morning
dosage [SMD], single evening dosage [SED], and dosages
ingested on 3 consecutive evenings [CED]). Results from Part A
are as follows. Blood buffering in the 0.1 gkg21 condition was
significantly lower than the 0.2 gkg21 and 0.3 gkg21 conditions
(p , 0.002), but there was no significant differences between
the 0.2 gkg21 and 0.3 gkg21 conditions (p = 0.34). Although
the blood buffering was relatively constant in the 0.1 and 0.2
conditions, it was significantly higher at 60 minutes than at 100
minutes and 120 minutes in the 0.3 gkg21 condition (p , 0.05).
Results from Part B are as follows. Blood buffering for SMD was
significantly higher than for SED and CED (p , 0.05). Blood
buffering in the SMD condition was significantly lower at 17:00
hours than at 11:00 hours (p = 0.007). The single 0.2 and 0.3
gkg21 NaHCO3 dosages appeared to be the most effective for
increasing blood-buffering capacity. The 0.2 gkg21 dosage is
Address correspondence to Dr. Jason Siegler, [email protected].
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best ingested 40 to 50 minutes before exercise and the
0.3 gkg21 dosage 60 minutes before exercise.
KEY WORDS metabolic alkalosis, buffering capacity, soda
loading
INTRODUCTION
O
ver the past 3 decades, extensive research has
investigated the potential of sodium bicarbonate
(NaHCO3) ingestion for inducing metabolic
alkalosis and enhancing subsequent physical
performance (see McNaughton and colleagues [18] for a
recent review). Early research reported that NaHCO3
loading was effective for improving the capacity for shortterm, high-intensity exercise (2,17,18), whereas more recent
studies have shown that NaHCO3 also can enhance performance during aerobic endurance and prolonged, intermittent high-intensity exercise (3,19,23).
The performance-enhancing effects of NaHCO3 are
associated largely with the degree of metabolic alkalosis
(12). The contemporary viewpoint is that, during highintensity exercise, the increased alkalosis attenuates the rate
of increase in free protons (H+) in the sarcoplasm, thereby
reducing the competition on the ionizable binding sites of the
actin/myosin complex, as well as delaying sarcoplasmic
reticulum dysfunction with regard to Ca2+ release and uptake
(1,7,24). This, in turn, is thought to delay the onset of fatigue
during high-intensity exercise (1,7,22,24).
The degree of metabolic alkalosis is altered by the dosage and
timing of NaHCO3 ingestion. However, although much
research has investigated the types of exercise that are
enhanced with NaHCO3 ingestion, to date, there has been
limited research on the dosage and timing of NaHCO3 ingestion that optimizes metabolic alkalosis and the associated
ergogenic effects. This is important because doses between 0.2
and 0.3 gkg21 have commonly resulted in equivocal
performance findings (9,11,15,18,26). For example, Horswill
et al. (10) reported that dosages of 0.2 gkg21 or less were
ineffective for improving sprint performance, whereas
McNaughton (17) reported that, with dosages of 0.1, 0.2, 0.3,
0.4, and 0.5 gkg21, only 0.1 gkg21 did not significantly enhance
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Sodium Bicarbonate Ingestion Protocols
sprint performance. Dosages of 0.15 and 0.20 gkg21 have also
been reported by others to enhance performance (5,13).
In previous studies, the time between NaHCO3 ingestion
and exercise onset has ranged from 1 to 2 hours. However,
the rationale for using any particular time period is typically
not given but instead appears to have been arbitrarily chosen.
A limitation to this approach is that the time course of the
level of metabolic alkalosis may differ between various
dosages, and therefore, the ergogenic effect of NaHCO3 may
be moderated by the interaction of the dosage with the
timing of ingestion before exercise onset. Establishing the
level and time course of alkalosis obtained from different
NaHCO3 loading protocols would establish the relative
efficacy of each protocol for eliciting alkalosis and rationalize
the timing of ingestion before exercise onset. Two recent
studies investigated the time course of metabolic alkalosis
and reported that peak alkalosis occurred between 60 and
90 minutes postingestion (20,21). However, these studies
used only a 0.3 gkg21 dosage, so the time course and relative
alkalosis elicited by other dosages was not established.
The purpose of this study was to determine the bloodbuffering profile of various NaHCO3 loading protocols. The
efficacy of the various loading protocols was assessed by the
level of blood alkalosis. We hypothesized that the level and
timing of peak alkalosis would be different for the various
loading protocols.
METHODS
Experimental Approach to the Problem
The study was separated into 2 parts. In Part A, measures were
made of blood alkalosis throughout 120 minutes after the
ingestion of various single NaHCO3 dosages (0.3 gkg21,
0.2 gkg21, 0.1 gkg21, and placebo); and in Part B, similar
profiles were made after alternative NaHCO3 loading protocols (single morning dosage [SMD], single evening dosage
[SED], and dosages ingested on 3 consecutive evenings
[CED]). Within Parts A and B, the loading protocols were
implemented in a randomized (counterbalanced), singleblind manner, each separated by 1 week. For all trials, the
buffer solution (bicarbonate of soda, commercial grade
supplied by Tesco, Cheshunt, Hertfordshire, UK) was diluted
into 100 mL of a low-calorie, flavored cordial concentrate
(mixed with 400 mL of water) and consumed over a 10-minute
period. For the placebo trial in Part A, 0.045 gkg21 of NaCl2
was substituted for NaHCO3. These ingestion protocols have
been the most commonly used in previous research (18).
Subjects
Eight male volunteers with the following mean 6 SD characteristics completed all aspects of the investigation: age,
22.4 6 5.7 years; height, 179.8 6 9.6 cm, body mass, 76.3 6
14.1 kg. All subjects provided written informed consent in
accordance with the departmental and university ethical
procedures and following the principles outlined in the
Declaration of Helsinki. None of the subjects included in the
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study were currently taking any nutritional supplements or
on any prescription medication. Before the first laboratory
visit, subjects were instructed as to the importance of
nutritional intake and asked to control, record, and duplicate
their food intake for all trials (collected and reviewed but not
presented). In addition, all subjects were told to avoid spicy
foods and excessive intake of meat protein as well as consume
500 mL of water during each meal preceding a trial.
Procedures
Part A. Subjects reported to the temperature-controlled
laboratory (19–23°C) for testing on the prescribed day, at the
same time, for each of the 4 trials (0.3 gkg21 load, 0.2 gkg21
load, 0.1 gkg21 load, or placebo). Upon arrival to the initial
trial, a baseline capillary blood sample was obtained. Thereafter, the subjects ingested their prescribed solution over
a 10-minute period. Once consumed, a timer was started, and
the subjects then rested calmly for 120 minutes. Capillary blood
samples were obtained every 20 minutes for 120 minutes.
Part B. The 3 remaining trials followed the same pretest diet
guidelines, sampling, and measurement procedures as Part A.
The ingestion protocols were as follows: a) a single 0.3 gkg21
NaHCO3 dosage at 09:00 hours (SMD) on the morning of
testing; b) a single 0.3 gkg21 NaHCO3 dosage at 20:00 hours
(SED) the night before testing; and c) a single 0.3 gkg21
NaHCO3 dosage at 20:00 hours, but taken for 3 consecutive
evenings (CED) before testing. Again, each 0.3 gkg21
NaHCO3 dosage was diluted into 500 mL of a low-calorie,
flavored cordial and consumed over a 10-minute period. In
each loading protocol, subjects were required to report back
to the laboratory for capillary blood sampling at 11:00, 13:00,
15:00, and 17:00 hours.
Blood Sampling and Analysis
All blood samples were obtained aseptically by way of
capillary finger sticks. The hand was heated for 10 minutes
before all draws using a heating pad wrapped on the forearm.
This was implemented to increase blood flow and arterialize
capillary blood at the sampling site. Whole blood was
collected in a balanced heparin 200 mL blood gas capillary
tube for immediate analysis of pH, bicarbonate (HCO32), and
base excess (BE). The sample was immediately capped and
placed on ice until subsequent (always within 5 min of
collection) blood gas and acid-base analyses using a clinical
blood gas analyzer (OMNI 4 Blood Gas Analyzer, Roche
Diagnostics, Ltd., Sussex, UK). All measures were done in
duplicate, and the range of intraclass correlation coefficients
were 0.81 to 0.95, p , 0.01, for all dependent variables,
respectively.
Statistical Analyses
Statistical analyses were completed using SPSS for Windows
software (release 16.0; SPSS, Inc., Chicago, IL, USA). The
required sample size of 8 subjects was determined by prospective statistical power analysis using PASS 2008 software
(NCSS, LLC, Kaysville, UT, USA), with alpha and beta set at
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0.05 and 0.2, respectively. Blood acid-base (pH, HCO32, BE)
profiles were analyzed using two-way (condition 3 time)
analysis of variance (ANOVA) for repeated measures. A
Huynh-Feldt correction was applied when Mauchly’s test
indicated that the sphericity assumption for any particular
within-subjects effect was not plausible. One-way ANOVA
for repeated measures were used to analyze differences in
baseline values (pre-ingestion) between conditions for all variables. Sidak-adjusted post hoc tests were used for pairwise
comparisons where there was a significant F ratio for any
particular within-subject effect. Two-tailed statistical significance was accepted as p , 0.05.
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values of pH (F = 1.6; p = 0.21), HCO32 (F = 1.8; p = 0.17),
and BE (F = 1.6; p = 0.23). There were significant main effects
for condition for pH (F = 21.5; p , 0.001), HCO32 (F = 82.1;
p , 0.001), and BE (F = 88.9; p , 0.001). The placebo
condition resulted in significantly lower values than all other
conditions for all 3 variables (p # 0.02). The 0.1 gkg21
condition was also significantly lower than the 0.2 gkg21 (p =
0.002) and 0.3 gkg21 (p , 0.001) conditions for HCO32, and
the 0.1 gkg21 condition was significantly lower than the 0.3
gkg21 condition for BE (p , 0.001). There were significant
main effects for time for HCO32 (F = 6.6; p , 0.001) and BE
(F = 6.9; p , 0.001) but not pH (F = 1.8; p = 0.13). The
HCO32 concentration at 60 minutes was significantly higher
than at 100 minutes (p = 0.024) and 120 minutes (p = 0.023).
The BE was significantly higher at 60 minutes (p = 0.008) and
100 minutes (p = 0.039) than at 120 minutes. There were
also significant condition x time interaction effects for pH
RESULTS
Part A
Mean (SD) blood acid-base data are presented in Table 1. No
significant differences existed between conditions for baseline
TABLE 1: Mean (SD) values for blood pH, bicarbonate (HCO32) and base excess (BE) before ingestion (baseline) of
either a placebo or 0.1, 0.2, or 0.3 gkg21of sodium bicarbonate, and at 20, 40, 60, 80, 100 and 120 min post-ingestion.
Like superscript letters for any given variable indicate that the difference between conditions is statistically significant
(p , 0.05).
pH
Time
Placebo
Baseline
20
40
60
80
100
120
7.400 6 0.029
7.396 6 0.032*†
7.399 6 0.033*
7.401 6 0.019*†
7.395 6 0.030*†
7.406 6 0.012*†‡
7.392 6 0.029*†‡
0.1 gkg21
7.402
7.432
7.428
7.421
7.429
7.431
7.428
0.2 gkg21
6 0.015
6 0.020*
6 0.024†
6 0.018‡
6 0.015
6 0.018*§
6 0.017*
7.416
7.448
7.459
7.448
7.444
7.431
7.432
0.3 gkg21
6 0.019
6 0.024†
6 0.022*†
6 0.022*
6 0.016*
6 0.015†
6 0.022†
7.404 6 0.014
7.438 6 0.027
7.454 6 0.044
7.460 6 0.020†‡
7.448 6 0.035†
7.459 6 0.021‡§
7.443 6 0.023‡
HCO32(mmolL21)
Placebo
Baseline
20
40
60
80
100
120
25.1 6 1.2
25.0 6 0.9*†
25.1 6 0.6*†‡
25.1 6 1.0*†‡
25.6 6 1.2*†
25.6 6 0.8*†
25.0 6 0.8*†‡
0.1 gkg21
0.2 gkg21
0.3 gkg21
25.5 6 0.9
27.2 6 1.9
27.5 6 1.3‡§k
27.4 6 1.1*§k
27.1 6 1.0‡§
27.0 6 0.9‡§
26.8 6 0.6*
25.4 6 1.0
30.1 6 1.6*
30.3 6 1.1†§
30.0 6 1.4†§
29.5 6 1.1*‡
29.3 6 1.0*‡
28.9 6 1.4†
25.9 6 0.6
29.4 6 1.1†
30.8 6 1.3‡k
32.1 6 1.3‡k
31.6 6 2.0†§
30.3 6 1.1†§
30.2 6 0.9‡
BE (meqL21)
Placebo
Baseline
20
40
60
80
100
120
0.3 6
0.1 6
0.1 6
0.3 6
0.6 6
0.9 6
0.0 6
1.1
0.9*†‡
0.8*†‡
1.0*†‡
1.1*†
0.7*†
1.0*†‡
0.1 gkg21
0.2 gkg21
0.6 6 0.7
2.5 6 1.5*§
2.7 6 1.2*§
2.5 6 1.2*§
2.4 6 1.1‡§
2.4 6 0.9‡§
2.1 6 0.7*§
0.8 6 0.9
5.2 6 1.6†§
5.7 6 1.2†§
5.2 6 1.4†
4.7 6 0.9*‡
4.3 6 0.8*‡
3.9 6 1.3†
0.3 gkg21
1.0 6
4.5 6
6.2 6
7.0 6
6.6 6
5.7 6
5.3 6
0.6
1.3‡
1.7‡
1.2‡§
1.7†§
1.1†§
0.8‡§
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1.2 6 1.0†
0.9 6 1.0†
0.9 6 1.5†
1.1 6 0.9†
1.4 6 1.0*
1.3 6 1.2*
1.2 6 0.7*
0.6 6 0.6*
Figure 1. Ingestion profiles of HCO32 for 4 conditions. With exception of
placebo trial, all conditions were significantly higher than baseline. In
addition, the 0.3 gkg21 and 0.2 gkg21 conditions were significantly
higher than 0.1 gkg21 and placebo for all time points, whereas 0.1 gkg21
only differed from placebo.
SMD ¼ Single morning dosage; SED ¼ Single evening dosage; CED ¼ Consecutive evening dosages (three evenings).
0.9†
0.8†
1.8†
1.1†
25.9 6
25.9 6
25.7 6
25.8 6
6 1.1*
6 1.5*
6 0.9*
6 0.9*
26.1
26.3
25.8
25.4
6 1.0*†
6 1.2*†
6 1.4*†
6 1.1*†
30.5
29.0
28.5
27.5
6 0.023
6 0.022
6 0.019
6 0.019
7.412
7.405
7.406
7.407
6 0.020
6 0.015
6 0.025
6 0.020
7.418
7.404
7.414
7.406
0.026
0.020
0.010
0.015
7.447 6
7.434 6
7.416 6
7.418 6
11:00
13:00
15:00
17:00
Time
SMD
SED
CED
SMD
SED
CED
5.6
4.1
3.3
2.5
6 1.3*†
6 1.2*†
6 1.1*†
6 0.9*†
CED
SED
SMD
BE (meqL21)
HCO32(mmolL21)
pH
TABLE 2. Mean (SD) values for blood pH, bicarbonate (HCO32) and base excess (BE) at 11:00, 13:00, 15:00 and 17:00 hrs for the alternative sodium bicarbonate
loading protocols. Like superscript letters for any given variable indicate that the difference between conditions is statistically significant (p , 0.05). The interaction
term for pH did not quite reach statistical significance (F = 2.4; p = 0.06) so post hoc significances are not reported.
Sodium Bicarbonate Ingestion Protocols
(F = 2.0; p = 0.022), HCO32 (F = 3.5; p , 0.001), and BE (F =
4.1; p , 0.001) (see Table 1 for significant differences between
conditions at specific time points).
Part B
Mean (SD) blood acid-base data are presented in Table 2.
There were significant main effects for condition for pH (F =
6.2; p = 0.029), HCO32 (F = 107.8; p , 0.001), and BE (F =
81.6; p , 0.001). The mean value for the SMD condition was
significantly higher than for the SED and CED conditions for
each of the 3 variables (p , 0.05). There were also significant
Figure 2. Ingestion profiles of base excess (BE) for 4 conditions. Similar
to HCO32 condition, and with exception of placebo trial, all conditions
were significantly higher than baseline. The 0.3 gkg21 and 0.2 gkg21
conditions were significantly higher than 0.1 gkg21 and placebo for all
time points, whereas 0.1 gkg21 only differed from placebo.
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main effects for time for pH (F = 4.8; p = 0.011), HCO32 (F =
4.8; p = 0.011), and BE (F = 5.7; p = 0.005). The HCO32 and
BE were significantly lower at 17:00 hours than at 11:00
hours (both p = 0.007). Post hoc tests for time were all
nonsignificant for pH (p $ 0.12). There was a significant
condition x time interaction effect for HCO32 (F = 5.9; p ,
0.001) and BE (F = 6.5; p , 0.001), but the interaction term
for pH did not quite reach statistical significance (F = 2.4; p =
0.060) (see Table 2 for significant differences between
conditions at specific time points).
DISCUSSION
A main finding of this study was that throughout 2 hours after
ingestion of a single bolus of either 0.1, 0.2 or 0.3 gkg21
NaHCO3, blood-buffering capacity was, on average, significantly higher for the 0.2 and 0.3 gkg21 dosages than the
0.1 gkg21 dosage; however, there was no significant difference between the 0.2 and 0.3 gkg21 dosages. Furthermore,
the blood-buffering profile was relatively constant between
60 and 120 minutes postingestion for the 0.2 gkg21 dosage,
whereas the 0.3 gkg21 dosage, on average, peaked at 65 minutes and declined slowly thereafter (Table 1, Figures 1 and 2).
The time-to-peak blood buffering for the 0.3 gkg21 dosage
found in this study is similar to the 60 to 90 minutes reported
by 2 recent studies (20, 21). However, the time-to-peak
observed in the 0.2 gkg21 trial occurred markedly earlier
(approximately 40–50 min) than the higher load (Table 1).
Highlighting this difference is important because there have
been numerous studies that have incorporated the 0.2 gkg21
dose into their methodologic application yet have also begun
the exercise trial at 60 minutes or longer (5,10,17). This
discrepancy between time-to-peak of the 2 loads and the start
of exercise may explain some of the equivocal findings with
regard to the efficacy of NaHCO3 loading (12). Our findings
Figure 3. Ingestion profiles of HCO32 for 3 prolonged loading
conditions. Single morning dosage (SMD) condition was significantly
higher (p , 0.05) than single evening dosage (SED) and 3 consecutive
evenings (CED) conditions for all time periods (noted*).
Figure 4. Ingestion profiles of base excess (BE) for 3 prolonged loading
conditions. Single morning dosage (SMD) condition was significantly
higher (p , 0.05) than the single evening dosage (SED) and 3
consecutive evenings (CED) conditions for all time periods (noted*).
would suggest that to maximize the ergogenic potential of
0.2 gkg21 NaHCO3, exercise should begin no later than
50 minutes postingestion.
Although single boluses of 0.3 gkg21 NaHCO3 ingested
1 to 2 hours before exercise have been the most commonly
reported loading protocols in experimental research, several
recent studies have used variations of this protocol in
attempts to further increase the ergogenic potential. Bishop
and Claudius (3) implemented a ‘‘stacking’’ protocol,
whereby the overall NaHCO3 load remained 0.3 gkg21 or
greater but was split into smaller dosages (0.2 gkg21 ingested
at time 0 and again 70 min post initial ingestion, with exercise
starting at 90 min postingestion). This loading sequence
assumes that there is a stacking effect associated with
NaHCO3 ingestion. Interestingly, the HCO32 and BE profiles of the 0.2 gkg21 in the current study exhibited a plateau
at approximately 70 minutes (approximately 29 mmolL21)
and remained so for the final 50-minute profile (Table 1,
Figures 1 and 2). Whether the extracellular milieu has
reached some sort of homeostatic buffering level at this time
point remains debatable, but it is plausible that this plateau
may justify the concept of stacking NaHCO3 loads.
Two other studies have incorporated the stacking concept,
yet, instead of hours before exercise, they involved multiple
days of NaHCO3 loading before assessing exercise performance (6,14). Alternative NaHCO3 ingestion protocols are
attractive because they could combine both an increased blood
buffering capacity and a reduction in the negative side effects
associated with bolus ingestions ($0.3 gkg21 NaHCO3). In
Part B of the present study, we replicated some of the
alternative loading sequences used in previous research to
investigate their time course for blood buffering. The SMD
condition resulted in significantly higher blood buffering than
the SED and CED conditions, with the HCO32 and BE
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concentrations remaining significantly elevated until 13:00
hours (equivalent to 4 hr postingestion) (Figures 3 and 4).
Interestingly, the sustained HCO32 elevation observed up to
4 hours postingestion was similar to those levels elicited by
the 0.2 and 0.3 gkg21 dosages at 120 minutes in Part A. This
would further suggest that stacking the loading sequence
may be an effective practice for up to 4 hours post initial
ingestion. This has important practical implications not only
in terms of enhancing extracellular blood-buffering potential
but may also prove more tolerable for those individuals either
unfamiliar with the practice of NaHCO3 loading or those
susceptible to gastrointestinal (GI) distress.
The SED and CED loading results are in contrast with
those reported elsewhere using a similar multiday loading
protocol. Douroudos and colleagues (6) have recently used
a prolonged supplementation protocol (either 0.3 gkg21 or
0.5 gkg21) over a 5-day period. They observed an increase in
performance after the ingestion period (assessed using
a standard Wingate protocol) while reporting no negative
side effects. We were unable to obtain blood HCO32 or BE
concentrations consistent with those reported by Douroudos
and colleagues with 3 consecutive days of 0.3 gkg21 loading
(HCO32: Douroudos ;30 mmolL21 vs. current study ;26
mmolL21; BE: Douroudos ;5 meqL21 vs. current study ;1
meqL21). Methodologic discrepancies may explain some of
the differences. For example, it is unclear as to whether
arterial or venous blood samples were used in the Douroudos
et al. study (6). Regardless, the relatively low metabolic
alkalosis in both the SED and CED conditions in our study
indicate there is little ergogenic benefit from ingesting
NaHCO3 the day before (or several days before) and that
NaHCO3 should be ingested on the same day as the exercise
is being undertaken.
PRACTICAL APPLICATIONS
Our findings suggest that single boluses of either 0.2 or 0.3
gkg21 NaHCO3 result in similar buffering effects, but the 0.3
gkg21 dosage should be ingested approximately 60 minutes
before exercise, and the 0.2 gkg21 dosage should be ingested
between 40 and 50 minutes before exercise. These recommendations are based on the premise that the ergogenic
potential of NaHCO3 is associated with the degree of metabolic alkalosis (12). A NaHCO3 dosage of 0.1 gkg21 cannot
be recommended because the blood HCO32 concentration
was, on average, 7.0% lower than the 0.2 gkg21 dosage and
9.8% lower than the 0.3 gkg21 dosage. This is consistent with
the lack of ergogenic effect reported by McNaughton (17) for
a single bolus of 0.1 gkg21 NaHCO3.
In addition, if a stacking approach is implemented using 0.3
gkg21 of NaHCO3, then the loading should be separated by
approximately 90 minutes to allow for the initial bolus load to
plateau (Table 1). Conversely, if stacking with 0.2 gkg21, then
we would recommend the second dose at approximately 70
minutes post initial ingestion. It must be stressed that no
research has been published using more than 2 NaHCO3
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loading sequences in 1 day, and we are not advocating
loading above this volume because of potentially dangerous
and harmful side-effects (i.e., muscle weakness, muscle spasms,
convulsions, or seizures). Because the use of NaHCO3 loading as a supplement appears widespread (4,8,25), we also
recommend that athletes generally should not ingest single
NaHCO3 dosages greater than 0.3 gkg21 because these are
associated with an appreciable increase in the incidence of
other, less-harmful negative side-effects (17). In terms of
athletic performance, we also recommend that athletes
experiment with their tolerance to different dosages because
higher dosages are more likely to elicit acute symptoms of GI
distress, bloating, or diarrhea (14). In the current study, only 3
of the subjects reported GI discomfort (e.g., bloating) within
the first 30 minutes of the 0.3 gkg21 acute load (Part A), but
these were only minimal and subsided after 45 minutes. The
GI distress issue is very relevant in terms of the performance
potential, but with doses at 0.3 gkg21 or below, others have
reported very little to no GI problems (17). Another issue
concerning NaHCO3 loading strategies is that of the
potential for dehydration. Because it is widely recognized
that dehydration can have a negative impact on performance
and because the standard NaHCO3 supplementation protocol is equivalent to approximately 18 to 25 g, there is
potential for inducing an osmotic gradient in the stomach
and small intestines and consequently a loss of intracellular
H2O. Thus, we would recommend monitoring hydration
(ideally by plasma/urine osmolality or urine-specific gravity)
before and during any loading sequence, especially during
prolonged exercise or during exposure to environmental
stress (e.g., heat). This will provide valuable information in
terms of the necessary fluid intake to maintain athletes’
respective hydration status before exercise. Finally, athletes
should be advised to ingest the NaHCO3 on the same day as
the exercise is being performed and that multiday NaHCO3
loading protocols do not provide any additional buffering
potential.
ACKNOWLEDGMENTS
The author’s thank the volunteers who participated in the
study. The authors have no undisclosed professional relationships with companies or manufacturers that would benefit
from the results of the present study. The results of the present
study do not constitute endorsement of the product by the
authors or the NSCA.
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