The effects of sodium citrate on repeated maximal cycling bouts

<strong>The</strong> <strong>effects</strong> <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> on repeated maximal cycling bouts
M.J. Crowe*
James Cook University, Townsville, Australia
INTRODUCTION: Fatigue during anaerobic performance is <strong>of</strong>ten the result <strong>of</strong> lactic acid build up and subsequent
acidosis. Sodium bicarbonate is one <strong>of</strong> the main buffers <strong>of</strong> acid in the body and it acts by neutralising protons to form carbon
dioxide and water. Oral ingestion <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> is known to increase blood bicarbonate levels and blood pH (Tiryaki &
Atterbom, 1995; Potteiger et al., 1996; Ball & Maughan, 1997). However, the possible ergogenic <strong>effects</strong> <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> on
anaerobic performance remain equivocal.
In general, studies investigating doses <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> <strong>of</strong> less than 0.4 g/kg body weight have failed to show any
ergogenic effect. A 0.3 g/kg body weight dose <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> did not affect mean and peak power and total work in a 3 x
30 s Wingate anaerobic test (Parry-Billings & MacLaren, 1986), repeated 45 s bouts <strong>of</strong> cycling (van Someren et al., 1998),
cycle time to exhaustion at 100% VO2 max (Ball & Maughan, 1997) or 600 m run time (Tiryaki & Atterbom, 1995) compared to
a placebo.
Although more positive evidence exists for <strong>sodium</strong> <strong>citrate</strong> as an ergogenic aid at or above doses <strong>of</strong> 0.4 g/kg body weight,
there are still contradictory findings. Isometric knee extensions were sustained for significantly longer after ingestion <strong>of</strong> 0.4
g/kg body weight <strong>sodium</strong> <strong>citrate</strong> compared to a placebo (Hausswirth et al., 1995). Run time to exhaustion at 120% VO2 peak
was also significantly increased in comparison to a placebo with 0.5 g/kg body weight <strong>sodium</strong> <strong>citrate</strong> (Linossier et al., 1997).
Interestingly, two studies have shown elevated blood lactate levels following intense exercise with 0.5 g/kg body weight
<strong>sodium</strong> <strong>citrate</strong> in comparison to a placebo but no increase in performance (Ibanez et al., 1995; Potteiger et al., 1996).
Performance on five repeated 60 s cycling sprints was also unaffected by a 0.5 g/kg body weight dose <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong>
compared to a placebo (Cox & Jenkins, 1994).
Timing <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> ingestion relative to commencement <strong>of</strong> exercise may be partly responsible for the lack <strong>of</strong>
consistent findings with higher doses <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong>. Potteiger et al. (1996) investigated the timing <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong>
absorption and reported that blood pH was significantly increased 50 minutes after consumption <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> and that
pH peaked at 100-120 minutes post-ingestion. A number <strong>of</strong> studies utilising a dose <strong>of</strong> 0.4 g/kg body weight or greater have
shown positive ergogenic <strong>effects</strong> <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> with 90 or 120 minutes between ingestion and exercise (Hausswirth et al.,
1995; Linossier et al., 1997; McNaughton & Cedero, 1992). Ibanez et al. (1995) used a three-hour absorption time which
may have been too long as there were no reported ergogenic <strong>effects</strong> <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> in this study. However, Cox and
Jenkins (1994) and Potteiger et al. (1996) also used 90 and 120-minute absorption times respectively and found no
ergogenic <strong>effects</strong> <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong>. Thus, other factors must underlie the variable <strong>effects</strong> <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> on anaerobic
performance.
Duration <strong>of</strong> exercise may play a role in determining the effectiveness <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> as an ergogenic. McNaughton and
Cedero (1992) found a positive effect <strong>of</strong> 0.5 g/kg body weight <strong>sodium</strong> <strong>citrate</strong> on maximal cycling <strong>of</strong> 120 s and 240 s duration
but no effect when exercise duration was 10 s or 30 s. <strong>The</strong>refore, exercise must be <strong>of</strong> sufficient duration to elicit a substantial
lactic acid response.
STATEMENT OF THE PROBLEM: Equivocal evidence exists as to the potential ergogenic <strong>effects</strong> <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> on
anaerobic performance. Doses <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> equal to or greater than 0.4 g/kg body weight with an absorption time <strong>of</strong> 90-
120 minutes and exercise duration longer than 30 s appear to enhance anaerobic performance. <strong>The</strong>refore, this study aimed
to investigate the <strong>effects</strong> <strong>of</strong> a 0.5 g/kg body weight dose <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> on three repeated 30 s maximal cycling bouts with
an absorption time <strong>of</strong> 90 minutes. Under these conditions, it was expected that <strong>sodium</strong> <strong>citrate</strong> would cause an increase in
peak power, total work and blood lactate in comparison to a placebo.
METHODS: <strong>The</strong> subjects in this study were 20 healthy students (12 male and 8 female). <strong>The</strong> mean (± SD) age <strong>of</strong> the
subjects was 22.3 ± 3.8 years and mean body weight was 75.5 ± 18.9 kg. Participation was on a volunteer basis with
subjects providing informed consent after the procedures <strong>of</strong> the study were explained. <strong>The</strong> study was approved by the
James Cook University Ethics Committee.
<strong>The</strong> subjects first performed a familiarisation session where they were asked to warm up on a cycle ergometer (Repco)
at a moderate pace for 3-5 minutes. <strong>The</strong> subjects then commenced a 3 x 30 s maximal cycle test with verbal encouragement
from the experimenters and 30 s rest periods between bouts. No measurements were taken during this session.
<strong>The</strong> subjects returned to the laboratory seven days after the familiarisation session to perform baseline testing. <strong>The</strong>
protocol for baseline testing was identical to that <strong>of</strong> the familiarisation session. Peak heart rate was recorded for each 30 s
exercise bout using a heart rate monitor (Polar Vantage). Peak power (watts/kg) and total work (joules/kg) were recorded
using a Repco Supermonitor for each exercise bout. A finger prick blood sample was taken at three and six minutes after
completion <strong>of</strong> the third 30 s exercise bout to ascertain blood lactate levels using an Acusport blood lactate tester. <strong>The</strong> highest
blood lactate value from the three and six minute samples was used in the analysis. <strong>The</strong> subjects were encouraged to
continue cycling at a slow pace for several minutes to warm down after completion <strong>of</strong> the third 30 s exercise bout.
Seven days after baseline testing, the subjects returned to the laboratory and consumed either a 0.5 g/kg body weight
dose <strong>of</strong> <strong>sodium</strong> <strong>citrate</strong> dissolved in a cordial drink (n=10, 7 males and 3 females) or a cordial–<strong>sodium</strong> chloride (0.045 g/kg)
placebo (n=10, 5 males and 5 females). Allocation <strong>of</strong> <strong>citrate</strong> or placebo was performed in a double-blind manner. A period <strong>of</strong>