The Reproducibility of 4-km Time Trial (TT) Performance Following Individualised Sodium Bicarbonate Supplementation: a Randomised Controlled Trial in Trained Cyclists
Gough et al. Sports Medicine - Open
The Reproducibility of 4-km Time Trial (TT) Performance Following Individualised Sodium Bicarbonate Supplementation: a Randomised Controlled Trial in Trained Cyclists
Lewis Anthony Gough 0
Sanjoy Kumar Deb 0
Andy Sparks 0
Lars Robert McNaughton 0
0 Sports Nutrition and Performance Group, Department of Sport and Physical Activity, Edge Hill University , Ormskirk, Lancashire L39 4QP , UK
Background: Individual time to peak blood bicarbonate (HCO3−) has demonstrated good to excellent reproducibility following ingestion of both 0.2 g kg−1 body mass (BM) and 0.3 g kg−1 BM sodium bicarbonate (NaHCO3), but the consistency of the time trial (TT) performance response using such an individualised NaHCO3 ingestion strategy remains unknown. This study therefore evaluated the reproducibility of 4-km TT performance following NaHCO3 ingestion individualised to time to peak blood bicarbonate. Methods: Eleven trained male cyclists completed five randomised treatments with prior ingestion of 0.2 g kg −1 (SBC2) or 0.3 g kg−1 BM (SBC3) NaHCO3, on two separate occasions each, or a control trial entailing no supplementation. Participants completed a 4-km cycling TT on a Velotron ergometer where time to complete, power and speed were measured, whilst acid-base blood parameters were also recorded (pH and blood bicarbonate concentration HCO3−) and lactate [La−]. Results: Alkalosis was achieved prior to exercise in both SBC2 and SBC3, as pH and HCO3− were greater compared to baseline (p < 0.001), with no differences between treatments (p > 0.05). The reproducibility of the mean absolute change from baseline to peak in HCO3− was good in SBC2 (r = 0.68) and excellent in SBC3 (r = 0.78). The performance responses following both SBC2 and SBC3 displayed excellent reproducibility (r range = 0.97 to 0.99). Conclusions: Results demonstrate excellent reproducibility of exercise performance following individualised NaHCO3 ingestion, which is due to the high reproducibility of blood acid-base variables with repeat administration of NaHCO3. Using a time to peak HCO-3 strategy seems to cause no dose-dependent effects on performance for exercise of this duration and intensity; therefore, athletes may consider smaller doses of NaHCO3 to mitigate gastrointestinal (GI) discomfort.
Buffering; Alkalosis; Performance; Acid-base balance; Ergogenic aids; Reliability
Time to peak blood bicarbonate (HCO3−) induced via
ingestion of sodium bicarbonate (NaHCO3)
produces consistent physiological responses prior
to, during and post-exercise.
Four-kilometre TT performance displays excellent
reliability following repeat administration of 0.2 and
0.3 g kg body mass (BM) NaHCO3 individualised to
time to peak HCO3.
Athletes need to be aware that the gastrointestinal
(GI) discomfort response is varied even with
repeated administration; therefore, this needs to
Personalised nutrition has gathered recent attention as
individual characteristics (i.e. genetics, training status and
nutrition) can potentially improve or reduce the
physiological adaptation from the same intervention [
Through personalising nutrition strategies, both the
individual bioavailability and bioefficacy can be quantified to
maximise the effects of an intervention within individuals
]. This concept can also be applied to the use of
nutritional ergogenic aids aimed to enhance human physiology
and exercise performance; however, common practice of
ergogenic aid research determines the effectiveness of a
single treatment by evaluating the mean differences
between groups or trials [
]. As a result, the inter- and
intra-individual responses are seldom considered. To
account for this, repeat administration of the experimental
treatment is plausible, thereby allowing assessment of the
reproducibility of nutritional ergogenic aids [
method permits athletes to appropriately evaluate the
effectiveness of ergogenic aids and to assess if they can
provide consistent benefits to exercise performance upon
repeated use during training and/or competition .
The use of over-the-counter sodium bicarbonate
(NaHCO3) is one example of a supplement that allows
for repeated administration by representing a low cost
and easy digestion. Primarily, NaHCO3 is used as an
ergogenic aid to mitigate the effects of metabolic
acidosis (i.e. decline in pH) by increasing bicarbonate
(HCO3−) buffering capacity during short
distance/duration high-intensity exercise of between 1 and 10 min
]. Traditionally, NaHCO3 is administered in a single
0.3 g kg−1 body mass (BM) dose at a standardised time
prior to exercise ranging between 1 and 4 h [
26, 32, 34
It was originally suggested that the point of peak
alkalosis (measured by either peak pH and/or HCO3−)
occurred between 60 and 90 min post NaHCO3 ingestion
29, 32, 34
]. This same peak has also been suggested to
occur up to 180 min in other studies however [
6, 22, 35
whilst more recently, it has been shown to range between
40 and 140 min following both 0.2 and 0.3 g kg−1 BM
]. These data therefore suggest that there is a
large individual variation in time to peak alkalosis.
Consequently, some athletes may not be ingesting this
supplement at a time that corresponds to their peak buffering
capacity, which might limit the resulting ergogenic effect.
To account for such inter-individual variation an
individualised NaHCO3 strategy has recently been
recommended, which entails administering NaHCO3 at a time
point to ensure peak pH and/or HCO3− concentrations at
the beginning of exercise [
10, 14, 22, 28, 33
identifying peak alkalosis, it ensures that the HCO3− buffering
capacity is maximised, compared to a standardised ingestion
strategy where some participants may not begin exercise
at peak alkalosis. This methodological alteration may
therefore account for some of the equivocal
performance data which has been observed using NaHCO3
5, 13, 16, 32
]. Gough et al.  have displayed using
an individualised NaHCO3 time to peak strategy
that time to peak blood HCO-3 was highly repeatable
using intraclass correlation coefficient (ICC) analysis
(r = 0.77 to 0.94). The authors also reported
the mean HCO3− change from baseline to peak was
+ 5.7 mmol l−1 following 0.2 g kg−1 BM NaHCO3,
which is greater than the + 3.9 ± 0.9 mmol l−1 mean
change reported in a meta-analysis from a 0.3 g kg−1
BM dose [
]. This suggests that using an
individualised NaHCO3 ingestion strategy may elicit more
reproducible biological acid-base balance changes,
whilst a smaller 0.2 g kg−1 BM NaHCO3 dose induces
a change in HCO3− greater than the mean change
observed using a standardised 0.3 g kg−1 BM NaHCO3
dose. This smaller dose therefore represents a viable
option for the athlete, and the performance responses
following this dose are worthwhile to determine.
A factor that may hamper the use of NaHCO3 in a
practical sense is the onset of gastrointestinal (GI)
discomfort. Common symptoms include nausea,
belching, diarrhoea and vomiting, which can have both
practical and perceived impacts on the efficacy of this
supplement for performance enhancements [
Therefore, whilst it is important to initially heighten the level
of peak alkalosis, it is of equal importance to mitigate GI
discomfort. One strategy to reduce the severity of GI
discomfort is a lower dose (0.2 g.kg-1 BM), which has
been shown to reduce the severity of the symptom
suffered compared to 0.3 g kg−1 BM [
]. This dose
might not have been used as widely in previous research
due to the previous standardised times of ingestion, and
the early findings of McNaughton  reporting
0.3 g kg−1 BM produced greater ergogenic benefits
compared to 0.2 g kg−1 BM NaHCO3. Nonetheless, with an
individualised ingestion strategy, an increase in HCO3−
(~ 5 mmol l−1) should be reached with a lower amount
of NaHCO3 (i.e. 0.2 g kg−1 BM NaHCO3), whilst also
reducing the severity of GI discomfort [
In studies utilising standardised NaHCO3 ingestion
strategies, equivocal performance responses have been
reported across consecutive repeated trials [
et al.  reported when four seperate cycling bouts at
110% peak power output until time to exhaustion (TTE)
were performed with ingestion of 0.3 g kg−1 BM
NaHCO3, ten participants improved performance in at
least one trial, whilst only one participant improved in
all trials. Although blood pH and HCO3− were generally
repeatable in this study, a factor contributing to this
variation may have been the exercise test employed. A
high variation in responses has been displayed in TTE
], particularly in untrained individuals which
feature in the Dias et al. [
] study, and compared to
time trial (TT) tests [
7, 9, 16, 24
]. The lack of consistent
improvements in response to NaHCO3 may therefore be
due to the exercise protocol adopted, not the failure of
NaHCO3’s buffering mechanism to enhance
performance. In a further study, Carr et al.  reported that
performance responses were repeatable for mean power
during a 2000-m rowing TT performance displaying a
typical error (TE) of 2.1%. The authors, however,
reported the change in HCO3− from baseline to
preexercise displayed a very large TE (2.5%) and coefficient
of variation (CV) (7%), which may explain why no
performance effect was observed. This evidence suggests
the blood responses following NaHCO3 may not be
consistent following 0.3 g kg−1 BM NaHCO3. Furthermore,
both Dias et al. [
] and Carr et al. [
] utilised a
standardised NaHCO3 ingestion strategy and only reported
mean blood responses, which may have adversely
affected the blood and performance responses and thus,
the interpretation of the data. Only two studies have
evaluated the repeatability of the performance responses
following acute ingestion of NaHCO3 and reported
equivocal findings, meaning further enquiry is required.
The aim of this study was therefore to investigate the
reproducibility of blood acid-base, performance and GI
discomfort responses following two individualised
Eleven trained male cyclists volunteered for a randomised,
double-blind, crossover design study (height 182 ± 8 cm,
body mass 86.4 ± 12.9 kg, age 32 ± 9 years, maximal
oxygen consumption (VO2max) 58.0 ± 3.8 ml kg min−1, peak
power 4.5 ± 0.5 W kg−1). The participant inclusion
required individuals to meet the criteria of ‘trained cyclist’
as outlined by De Pauw et al. [
], be between 18 and
50 years of age, training for a minimum of 4 h week−1 and
have 2 years continuous cycling experience. Participants
were also excluded if they had ingested any
intra/extracellular buffer in the prior 6 months before data collection.
Ethical approval was obtained from the Departmental
Research Ethics Committee, and each participant provided
written informed consent prior to any data collection,
with the research conducted in accordance with the
Declaration of Helsinki.
Participants visited the laboratory in a 4-h postprandial
state to limit confounding nutritional effects on exercise
performance and at the same time of day to control for
circadian rhythms [
]. Participation in any strenuous/
unaccustomed exercise and alcohol intake was
prohibited for the 24 h prior to each treatment arm. Caffeine
was also to be avoided for the 12 h prior. Compliance
with the above procedures was checked via written logs
of nutritional intake, and participants were asked to
replicate nutritional practices for subsequent trials
(adherence = 100%).
Determination of Maximal Oxygen Consumption and
Time to Peak Blood Bicarbonate
Participants initially completed an incremental exercise
test on an electromagnetically braked cycle ergometer
(Excalibur Sport, Lode, Netherlands) to determine
VO2max and peak power output (PPO). After a
selfselected warm-up, the cycling protocol began at 75 W
for 1 min and then increased by 1 W every 2 s
(30 W min−1) until the point of volitional exhaustion.
This was determined by the inability for the participant
to sustain their self-selected cadence for longer than 5 s,
whereby they were given an initial warning, and the test
was then terminated on the subsequent occurrence.
Two trials were conducted in a randomised order to
identify time to peak blood HCO3− following ingestion of
either 0.2 g kg−1 NaHCO3 (SBC2) or 0.3 g kg−1 BM
NaHCO3 (SBC3). This was ingested as a drink and
mixed with 400 ml of water and 50 ml double strength
blackcurrant sugar-free squash. The use of time to peak
HCO3− was utilised as this has displayed greater
reproducibility compared to time to peak pH [
]. Finger prick
capillary blood samples were taken prior to NaHCO3
ingestion in a seated position and collected within a
100μl heparin-coated glass clinitube for analysis of blood
pH and HCO3− (ABL800 BASIC, Radiometer Medical
Ltd., Denmark). Subsequent blood samples were drawn
every 10 min over a 180-min period to identify time to
peak HCO3−. The double-blind nature of the study was
maintained by a volunteer outside of the research team,
who identified the time to peak HCO3−.
Familiarisation and Experimental Treatment Arms
The participants then performed a 4-km TT
familiarisation trial, followed by a further five separate visits
requiring completion of the same exercise following
ingestion of either 0.2 g kg−1 BM NaHCO3 twice (SBC2a
and SBC2b), 0.3 g kg−1 BM NaHCO3 twice (SBC3a and
SBC3b) or a control treatment entailing no
supplementation in a randomised order. A control trial was
conducted to obtain a reference point measure of
performance. Blood samples were taken at rest, at time to
peak HCO3− and post-exercise to analyse blood pH and
HCO3−, with the addition of a 5-μl sample for blood
lactate [La−] (Lactate Pro 2, Arkray, Japan). Ingestion of
either SBC2 or SBC3 was completed within 10 min, and
participants remained seated and rested until their
respective time to peak. A questionnaire to assess the
severity gastrointestinal (GI) discomfort was used every
10 min until individual time to peak HCO3− [
Each TT was completed on a Velotron Racermate™ cycle
ergometer interfaced with Velotron 3D coaching software
(Racermate, USA). Frame geometry (handlebars, seat
position) and gear ratios were selected by the participant to
match their preferred riding style to be replicated for each
subsequent trial. Strong and consistent verbal
encouragement was provided throughout the TT. Participants were
blinded from the clock, but were provided with feedback
on distance covered, watts (W) and cadence (rev min−1)
via the display [
]. This feedback was provided as cyclists
used in this study were not habitually completing 4-km
TT distances in competition.
Shapiro-Wilk test and standard graphical methods (Q-Q
plots) were used to assess normality of the data, and the
Mauchly test was used for homogeneity and variance.
Both the severity and time to peak GI discomfort were
considered non-normally distributed by the respective
normality tests. Therefore, a Friedman rank test was
used as an alternative and is reported with z score
(significance) and effect size (d) calculated by Z/√n.
Interpretation was then considered as small (0.10), medium
(0.24) and large (> 0.37) [
]. Mean speed, power and
time to complete were compared between treatment
arms using a repeated measures analysis of variance
(ANOVA). Haematological data such as pH, HCO3− and
[La−] were analysed using a two-way (treatment × time)
repeated measures ANOVA. Post hoc comparisons were
determined by Bonferroni correction. Effect size is
reported as partial η2 value and considered trivial (< 0.20),
small (0.20–0.49), moderate (0.50–0.79) and large (≥
0.80) in accordance with the conventional Cohen’s d
Limits of agreement (LOA) with 95% percent limits and
Bland-Altman plots were initially used to determine if data
was heteroscedastic [
]. The repeatability of both blood
acid-base balance and performance responses to SBC2 and
SBC3 was determined using intraclass correlation
coefficients (ICC) with r value and significance level (i.e. p
value) as per previous recommendations [
Interpretation of reproducibility was categorised by the respective r
value with categories of poor (r ≤ 0.40), fair (r = 0.40–0.59),
good (r = 0.60–0.74) and excellent (r ≥ 0.74). Typical error
(TE) is reported and calculated using the method of
Hopkins , with categories of small (≤ 0.2–0.6), moderate
(0.6–1.2), large (1.2–2.0), very large (2.0–4.0) and
extremely large (≥ 4.0%) used to interpret the data.
Coefficient of variation (CV) was reported using SD/mean × 100.
Statistical procedures were completed using SPSS version
22 (IBM, Chicago, USA), and calculations were carried out
using Microsoft Excel 2013 (Microsoft Inc., USA). All data
are presented as mean ± SD unless otherwise stated.
Statistical significance was set at p > 0.05.
Reliability of Treatments
The blood responses following SBC treatments were
largely reproducible (Tables 1 and 2). Individual blood
responses displaying absolute changes from baseline to
peak pH and HCO3− are depicted in Table 3. The only
inconsistency observed was the absolute change in pH
from baseline to peak in SBC3, revealing a poor ICC.
Excluding that case, blood responses pre-, during and
post-exercise ranged from good to excellent for all SBC
treatments (ICC range r = 0.68 to 0.95).
Excellent reproducibility of time to complete the 4-km
TT was observed in both SBC2 (r = 0.97, p < 0.001) and
SBC3 (r = 0.99, p < 0.001) with a low TE (range = 0.3 to
0.5%; Table 4). Mean power displayed excellent
reproducibility in both SBC2 (r = 0.96, p < 0.001; TE = 0.6%)
and SBC3 (r = 0.98, p < 0.001; TE = 0.4%). Mean speed
also displayed excellent reproducibility in SBC2
(r = 0.97, p < 0.001; TE = 0.6%) and SBC3 (r = 0.98,
p < 0.001; TE = 0.4%). Eight participants reported
symptoms of GI discomfort (Table 5). The severity of GI
discomfort displayed good reproducibility in SBC2
(r = 0.72, p = 0.023; TE = 1.3%) in comparison to
excellent in SBC3 (r = 0.76, p = 0.017; TE = 1.3%). The time
to peak GI discomfort displayed excellent reproducibility
in both SBC2 (r = 0.99, p < 0.001; TE = 0.2%) and SBC3
(r = 0.84, p = 0.005; TE = 1.1%).
Effect of Treatment
In the initial treatments to identify time to peak
alkalosis, peak HCO3− was achieved between 40 and 110 min
(median 50 min) following SBC2 and between 40 and
100 min (median 70 min) following SBC3. There was a
large inter-individual variation as the CV range was
between 27 and 33% for SBC treatments. A +
5.5 ± 0.7 mmol l−1 change in HCO3− from baseline to
peak was observed following SBC2, compared to +
6.5 ± 1.3 mmol l−1 in SBC3, respectively (Table 2). Both
SBC treatments displayed a large CV ranging from 14 to
19%. In comparison, peak pH from baseline was
achieved between 50 and 80 min (median 60 min)
following SBC2 and between 50 and 90 min (median
70 min) following SBC3. Similarly, a large CV range was
also observed (18 to 22%). The change from baseline to
peak was + 0.07 ± 0.02 in SBC2 and + 0.09 ± 0.03 in
SBC3, again with a large CV from 29 to 34% (Table 2).
Following NaHCO3 ingestion, HCO3− was greater
compared to baseline in both SBC2 and SBC3, revealing a
main effect for time (p < 0.001, η2 = 0.932); however, no
difference between treatments was observed (p = 0.184,
η2 = 0.010; Table 2). This trend was similar for pH with
a main effect for time (p ≤ 0.001, η2 = 0.983) and no
difference between SBC treatments (p = 0.512,
η2 = 0.003). During exercise, there was no difference in
the decline of HCO3− following both SBC2 and SBC3
(p = 0.251, η2 = 0.129). Post-exercise [La−] also displayed
no difference between SBC treatments (p = 0.494,
η2 = 0.076; Table 2).
The time to complete the 4 km distance was similar
for both SBC2 (combined mean = 373.6 ± 13.3 s) and
SBC3 (373.5 ± 13.1 s) (mean diff = 0.01 s; p = 0.929,
η2 = 0.015; Table 3). Compared to the control treatment
arm, both SBC2 and SBC3 produced faster completion
times (mean difference SBC2 = − 8.0, p ≤ 0.001 and
8.8 s, p = 0.006; SBC3 = − 8.2, p = 0.005 and 8.6 s,
p = 0.006). There was no difference between SBC2 and
SBC3 for either mean power (p = 0.966, η2 = 0.009) or
mean speed (p = 0.746, η2 = 0.040). Severity of GI
discomfort in SBC3 was marginally greater (3.4 ± 3.0
and 4.6 ± 3.6) compared to SBC2 (2.8 ± 3.4 and
1.4 ± 1.5), however not significantly (z = 0.268, d = 0.08)
(Table 5). Likewise, time to peak GI discomfort was
around 20 min later in SBC3 (41 ± 27 and 43 ± 31 min)
compared to SBC2 (23 ± 25 and 20 ± 24 min), although
again not significantly (z = 0.197, d = 0.06; Table 5).
The aim of this study was to investigate the
reproducibility of both blood acid-base analytes and performance
responses following repeated ingestion of NaHCO3. The
present study is the first to demonstrate that both the
physiological and performance responses are reproducible
when the ingestion time for NaHCO3 is determined by
individual time to peak HCO3. This provides a legitimate
and workable strategy to elicit consistent performance
responses on exercise of this duration and intensity. The
primary findings are in contrast to those of the
previous research which has reported large inter- and
intra-individual variability in both performance
] and blood acid-base responses [
following a standardised NaHCO3 ingestion strategy. It
would therefore appear that an individual time to
peak HCO3− ingestion strategy is more efficacious in
eliciting consistent responses.
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Performance following NaHCO3 displayed excellent
reproducibility within the trained cyclist cohort used in
this study. The TE values for the time to complete the
4-km cycling TT in the present study are consistent with
a previous investigation of the reliability of TT cycling of
the same distance without NaHCO3 ingestion. Stone et
] reported a TE of 0.9% which is similar to both
the SBC conditions in the present study (TE ≤ 0.5%),
whilst mean speed also displayed similar TEs (< 1%).
These consistent values may be evident due to the high
training status of the cyclists used in each respective
study and the well-reported reliability of 4 km TT
cycling performance under laboratory conditions [
1, 23, 38
The present study data suggests the inclusion of
NaHCO3 did not compromise the reliability of the
performance responses, and therefore, it can be
recommended to elicit consistent performance responses
during this type of exercise. The present study also
displays the intra-individual variation between
conditions (i.e. SBC2 vs. SBC2). The intra-individual variation
was larger in SBC2 than in SBC3, although this was
largely due to participant 4 who displayed an 11-s
difference between the two SBC2 treatments. With
participant 4 removed from the analysis, a 3-s change would
have occurred which is more akin to SBC3. In contrast,
four of the sample reported a difference < 1 s between
SBC conditions. Athletes should therefore be aware of
this variation and monitor accordingly if they consider
using NaHCO3 on a consistent basis.
The primary findings agree with Carr et al. [
reported a low TE (2.1%) for 2000 m rowing ergometry
following NaHCO3. In contrast, a lack of repeatability
was observed in a later study [
] reporting a mean CV
of 7.4 ± 3.2% (range = 2.5 to 14.8%) and large
intraindividual variation following NaHCO3. This is
considerably higher than the CV of Carr et al. [
] (1.6%) and the
present study (3.5%), which is likely due to the lower
training status of the participants used by Dias et al.
]. Equally, both the study of Carr et al. [
] and the
present study used TT simulation compared to a cycling
TTE protocol at 110% peak power output [
]. It is
suggested the ‘open-ended’ nature, the lack of control over
power output and motivational differences during a TTE
test explain the greater variation compared to TT
]. In a study by Saunders et al. [
an identical protocol as used by Dias et al. [
excellent test-retest reliability in ICC analysis (r = 0.88),
suggesting the exercise protocol did not negate the
reliability of responses following NaHCO3. It is more
likely, therefore, that the training status of participants
may have caused the greater variation in responses
compared to that of Carr et al.’s [
] and the present study,
as a trained athlete is likely to be able to produce a
similar effort compared to a recreationally active participant.
The present study reports similar reproducibility of
blood acid-base balance variables following NaHCO3 in
previous studies [
]. Carr et al.  reported a high
variation in HCO3− post-supplementation (TE = 2.4%),
whilst Dias et al. [
] highlighted a discrepancy of
0.02 pH units between two NaHCO3 treatment arms.
Likewise, the present study reported similar
inconsistencies such as a 0.03 pH unit discrepancy between the
SBC3 individual TTP experiment and SBC3, and a
0.9 mmol l−1 HCO3− discrepancy in the same SBC3
treatment. Whether such small discrepencies are practically
meaningful however, is abtruse. Nontetheless, individual
analysis revealed a small number of inconsistencies in
blood acid-base balance, as participant 4’s absolute
HCO3− change from baseline to peak was + 4.7 mmol l−1
in SBC2a, compared to a + 7.2 mmol l−1 change in
SBC2b. Likewise, the change from baseline to peak for
participant 8 was + 2.3 mmol l−1 different in SBC3 (+ 6.5
vs. + 4.2 mmol l−1). Some degree of inconsistency was
subsequently evident in performance times, particularly
with participant 4, who was around 11 s slower in
SBC2a than in SBC2b, whereas participant 8 was slower
in SBC3a by around 3 s, despite the greater change in
HCO3−, compared to SBC3b. These inconsistencies add
to previous findings that have reported whilst the
majority of blood responses were reproducible, some
individuals display large variability following NaHCO3 [
Given these inconsistencies, individuals should monitor
the performance effects following NaHCO3 ingestion
across multiple trials to ensure similar responses are
The physiological responses pre, during and post the
TTs displayed good to excellent reproducibility following
both NaHCO3 doses used in this study. During exercise,
the change in HCO3− was highly repeatable for all SBC
conditions and the values were reflective of a recent
study following NaHCO3 during a 3-min ‘all-out’ cycling
test compared to a placebo [
]. Of particular interest is
the lack of a difference in blood responses during
experimental trials between the NaHCO3 doses in the present
study. The absolute HCO3− change from baseline was
similar for both SBC conditions, as only a 0.5 mmol l−1
greater increase was observed in SBC3 compared to
SBC2. Likewise, the increases in pH following NaHCO3
ingestion were similar between the SBC conditions. This
may explain why no dose-dependent performance effects
were observed in this study, as buffering capacity would
have been increased to a similar extent and therefore
lead to equal amounts of H+ buffering by circulating
HCO3−. Moreover, in respect of blood lactate, a low TE
range of 0.7 to 0.8% was displayed along with excellent
ICC values (r = 0.91 to 0.92). This is in contrast to
previous research displaying a TE of ~ 7% [
some small inconsistencies were apparent as participants
6, 8 and 10 reported values with at least 2 mmol l−1
difference in SBC2, whilst participants 3 and 9 displayed
this effect in SBC3. The reasons for this are unclear,
although it may be due to the technical error associated
with the lactate analyser used in this study [
Nonetheless, the present study displays that the physiological
responses are consistent with repeated use of NaHCO3
meaning the primary acting mechanisms for
performance enhancement should be in place if the athlete is
seeking a performance enhancement.
A unique finding of the present study is that the
performance responses following NaHCO3 were not dose
dependent, akin to previous research [
]. The fastest
4km TT completion time was observed in SBC2b although
the other SBC treatments were not significantly slower
(range + 0.2 to 0.9 s; % diff < 0.5%), suggesting a smaller
dose of NaHCO3 may be plausible to prompt similar
physiological and performance responses. A consideration
of this study however is that no placebo treatment was
utilised to identify if these responses were ergogenic. The
central aim of the study was to quantify the reproducibility of
performance following repeated NaHCO3 ingestion;
therefore, this comparison was not included. Nonetheless, a
control trial was conducted and our SBC conditions were
significantly faster by 2.1 and 2.3% for SBC2 and 2.2 and
2.3% faster for SBC3. This suggests an ergogenic effect was
apparent, in agreement with other studies using a time to
peak alkalosis NaHCO3 ingestion strategy [
further research should address this by comparing such
performance responses to a placebo.
A practical benefit of utilising smaller doses of
NaHCO3 is to minimise GI discomfort, as smaller doses
have been shown to reduce the severity of symptoms
]. McNaughton  reported anecdotally as the
amount of NaHCO3 ingested increased from 0.1 to
0.5 g kg−1 BM the severity of GI discomfort increased,
however since this study, comparisons between doses
have been sparse. Indeed, the severity and time to peak
GI discomfort was reproducible in the present study
using ICC analysis (ICC range r = 0.72 to 0.99); however,
in some cases, the symptom suffered varied despite a
similar rating of severity and time to peak. Participant 8
for instance suffered from nausea and bloating in SBC3a
but then suffered diarrhoea and bowel urgency in
SBC3b. The reasons for the discrepancies in symptoms
remain inconclusive, as previous research seemed to
suggest it was not linked to pre-exercise nutrition
(carbohydrate, protein, fat and sodium intake) or the
change in sodium (Na+) following NaHCO3 [
although further research is warranted. Nonetheless, this
provides a challenge to the individual considering
routine use of NaHCO3 as the symptom suffered may
change with no clear pattern, which subsequently could
impact the ability or desire to perform exercise, although
the time to peak GI discomfort does seem to occur at
the same time point. This influence of GI discomfort
should therefore be monitored during training prior to
use in competition.
This study is the first to display consistent performance
responses from NaHCO3 ingestion when exercise begins
at the individual time of peak HCO3−. These datum
support the use of individualised NaHCO3 supplementation
strategies prior to performance to elicit reproducible
physiological and performance responses. The use of
personalised nutrition to maximise the bioavailability of
HCO3− and produce reliable responses in exercise that is
competitive in nature is therefore recommended.
Accompanying this finding, both 0.2 and 0.3 g kg−1 BM
NaHCO3 produced similar blood acid-base balance and
performance reliability, with no difference between
doses, suggesting both amounts can be used as an
ergogenic strategy. Lastly, the use of NaHCO3, irrespective
of dose and repeated ingestion, appears to have a varied
response on GI discomfort. Athletes should therefore
monitor these responses, in an attempt to mitigate the
impact of GI discomfort on exercise performance.
The first author would like to thank Dr. Craig Bridge for his input into the
study design and kind words of advice.
No funding was received for this study.
Availability of Data and Materials
Supporting data is available on request (see corresponding author email).
Disclosures and Grants
Lewis Gough, Sanjoy Deb, Andy Sparks and Lars McNaughton can confirm
that there are no conflicts of interest, and no grants or funding were
received for this work.
LG designed the study initially, with contributions from LM, AS and SD. The
data collection was completed by LG and SD. The manuscript was written
by LG, with feedback provided by LM, AS and SD. All authors read and
approved the final manuscript.
Ethics Approval and Consent to Participate
Ethical approval was granted by the Department Research Ethics Committee
(ref: SPA-REC-2015-366). Each individual participant provided informed consent
prior the beginning of the study.
Consent for Publication
Consent was provided from each participant for the results of this study to
Lewis Gough, Sanjoy Deb, Andy Sparks and Lars McNaughton can confirm
that there are no conflicts of interest.
Springer Nature remains neutral with regard to jurisdictional claims in published
maps and institutional affiliations.
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