International Journal of Sport Nutrition and Exercise Metabolism, 2014, 24, 296 -304 http://dx.doi.org/10.1123/ijsnem.2013-0127 © 2014 Human Kinetics, Inc
www.IJSNEM-Journal.com ORIGINAL RESEARCH
Influence of Caffeine and Sodium Citrate Ingestion on 1,500-m Exercise Performance in Elite Wheelchair Athletes: A Pilot Study Joelle Leonie Flueck, Samuel Mettler, and Claudio Perret The aim of this study was to investigate whether caffeine and/or sodium citrate have an ergogenic effect on the 1,500-m exercise performance in elite wheelchair athletes. A placebo-controlled, randomized, cross-over and double-blind study design was conducted with the four treatments placebo, caffeine, sodium citrate and the combination of caffeine and sodium citrate. Nine healthy, elite wheelchair-racing athletes (median: [min; max] age: 28 y [23; 54]; height: 173 cm [165; 188]; weight: 62.9 kg [48.9; 68.4], category T53/54) completed the study. All athletes were national team members, including several Paralympic Games, World and European Championship medalists. The athletes performed a 1,500-m time trial four times on a wheelchair training roller. Time to complete 1,500-m, pH, bicarbonate and sodium concentration as well as lactate concentration were measured. The time to complete 1,500-m was not significantly different between the four treatments (placebo: 170.6 s [141.7; 232.0]; caffeine: 179.5 s [134.8; 239.6]; sodium citrate: 178.3 s [136.4; 247.1]; combination: 177.6 s [136.1; 256.2]). However, pH and bicarbonate concentrations were significantly increased with sodium citrate ingestion compared with placebo. Moreover, maximal lactate concentrations were significantly higher in the caffeine and the combination treatment compared with placebo. The supplementation with sodium citrate and/or caffeine did not provide an ergogenic effect on the 1,500-m exercise performance in wheelchair elite athletes. Keywords: sports nutrition, wheelchair racing, spinal cord injury, ergogenic effect The positive ergogenic effect of caffeine or sodium citrate ingestion on exercise performance in healthy, able-bodied athletes is well-documented. Numerous investigations have shown an ergogenic effect of caffeine on high-intensity exercise performance (for review, see Burke, 2008). For example, the time to complete a 1,500-m run was 4.2 s faster with caffeine compared with placebo (Wiles et al., 1992). In another study (Wiles et al., 2006) a positive effect on a 1 km cycling time trial was observed. Ergogenic effects have also been reported with shorter performance times (e.g., 30 s cycling, 100 m swimming; Bell et al., 2001; Collomp et al., 1992; Woolf et al., 2008). Furthermore, basic salts like sodium citrate or sodium bicarbonate have been shown to improve highintensity exercise performance in different sports such as running, rowing, cycling and swimming (Lindh et al., 2008; Linossier et al., 1997; McNaughton & Cedaro, Flueck is with the Institute of Human Movement Sciences and Sport, and Mettler the Institute of Food Nutrition and Health, ETH Zurich, Zurich, Switzerland. Perret is with the Institute of Sports Medicine, Swiss Paraplegic Centre, Nottwil, Switzerland. Address author correspondence to Joelle Leonie Flueck at
[email protected].
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1992; Wilkes et al., 1983). For example, McNaughton (1990) reported a significant higher peak performance and total work in a 1min cycling time trial after the ingestion of sodium citrate compared with placebo. The same research group showed (1992) a significant higher power output in cycling performances lasting 120 s and 240 s after the ingestion of sodium citrate compared with placebo. A study (Potteiger et al., 1996) comparing sodium citrate and bicarbonate ingestion found no significant difference between peak blood pH after ingestion of these two supplements. McNaughton (1990) recommends preferring sodium citrate over sodium bicarbonate regarding the appearance of gastrointestinal side effects. Such side effects seem to occur less often after sodium citrate ingestion compared with sodium bicarbonate ingestion. To our knowledge, there is no study on the ergogenic effect of caffeine or basic salts like sodium citrate on the performance of spinal cord injured athletes. In general, only a few studies explored the influence of other supplements on exercise performance in athletes with impairment. These researchers have focused on creatine supplementation (Perret et al., 2006) and carbohydrate ingestion (Skrinar et al., 1982; Spendiff & Campbell, 2005). Furthermore, data from studies conducted with able-bodied participants could possibly not be transferred one-to-one to spinal cord injured individuals, because of
Caffeine and Sodium Citrate Supplementation in SCI 297
the physiological differences concerning active muscle mass (Maggioni et al., 2003; Nuhlicek et al., 1988), muscle fiber type distribution (Schantz et al., 1997) and gastrointestinal function (Krogh et al., 2000). For example, gastrointestinal transition time is prolonged in subjects with a spinal cord injury. Therefore, it was not sure if supplements could be absorbed in the time between the ingestion and the exercise testing in our elite wheelchair athletes. However, as the performance enhancing mechanisms of caffeine and sodium citrate supplements are basically the same as in able-bodied participants, ergogenic effects could be expected. Additional ergogenic effects of a combination of the two supplements might be expected, as the two supplements work via two different mechanisms. Sodium citrate increases the blood buffering capacity (Requena et al., 2005) and caffeine affects the sympathetic nervous system (Daniels et al., 1998; McMullen et al., 2011; Tarnopolsky, 2008) and energy supply (Costill et al., 1978; Graham & Spriet, 1995). To our knowledge, no study has investigated the influence of caffeine or sodium citrate supplementation in elite wheelchair athletes. Therefore, the aim of our study was to investigate whether caffeine or sodium citrate have ergogenic effects on the 1,500 m time trial performance in elite wheelchair athletes and whether the combination of these two supplements would be even more effective than the use of one single supplement.
Methods Participants Nine (six men and three women) healthy, elite wheelchair-racing athletes, including several Paralympic Games, World and European Championship medalists, participated in this study. All participants competed in
the category T53/54 and were national team members. The participants’ anthropometric data as well as the percentage fat mass are shown in Table 1. Exercise testing procedures and the equipment were familiar to all participants from previous studies or their own regular performance tests. The study was approved by the local ethical committee and written informed consent was obtained before the start of the study.
Study Design A double-blind, placebo-controlled, cross-over, randomized study was performed. Each subject performed a 1,500-m time trial on a wheelchair training roller (RehaBlitz, Uetendorf, Switzerland) four times. The four test conditions were placebo, caffeine, sodium citrate and the combination of sodium citrate and caffeine supplementation (Figure 1). Tests were separated by at least 48 hr Before the start of the testing phase, body mass was measured using a wheelchair scale (Busch BIT 650, Italy) and a bioimpedance analysis (Body Impedance Analyzer, BIA 101, AKERN, Pontassieve, Italy) was performed at least 2–3 hr after eating and after a 10 min complete rest in a supine position to determine body composition. Diet, sleep and training have been recorded by a questionnaire before every trial to guarantee equal testing conditions. Participants were prompted to standardize their last two main meals before every trial and to sleep at least seven hours the last two nights before the exercise testing. Training was the same every week with the testing day on the same day of the week. Athletes did not implement additional training sessions during the whole testing phase. The participants ingested a 700 ml solution enriched with sodium citrate or placebo, depending on the test condition, during a 30 min time slot, 120–90 min before the start of the time trial. Gelatin capsules filled with
Table 1 Anthropometric Data Participant #1
Gender
Age (y)
Height (cm)
Body Mass (kg)
Lesion level
AIS
Body Fat (%)
f
27
166
49.0
Th11
A
21.2
#2
m
32
165
67.0
Spina bifida
B
24.0
#3
m
28
173
60.6
L2
C
26.3
#4
m
54
178
62.9
Th4/5
A
13.3
#5
m
35
188
68.4
Th5/6
A
21.9
#6
m
26
173
65.0
Spina bifida
C
12.3
#7
f
39
168
48.9
Th12/L1
B
18.5
#8
m
23
180
68.0
Th5/6
A
9.8
#9
f
L1
B
20.5
26
170
50.1
Median
28
173
62.9
Minimum
23
165
48.9
9.8
Maximum
54
188
68.4
26.3
Note. AIS = American Spinal Injury Association Impairment Scale
20.5
298 Flueck et al.
Figure 1 — The study design with the four different supplementations.
caffeine or placebo were ingested one hour before the 1,500-m time trial. The warm up started 20 min before beginning the time trial. The warm up speed was selected by the participants, but it had to be repeated the same way for all four tests of a participant. Resting, as well as average and maximal heart rate during the 1,500-m was measured using a heart rate monitor (Polar 610i, Polar Electro, Kempele, Finland). The covered distance was recorded with a cyclometer (Cateye Astrale 8, Osaka, Japan) and the time to complete the 1,500-m time trial was measured with a stopwatch (Sportthieme stopwatch, Grasleben, Germany). Information about the distance covered was given to the athletes every 400 m and every 100 m in the last 400 m of the 1,500-m trial. They have not been verbally encouraged with the exception of these inputs and did not get any information about speed or time to complete the 1,500-m until the end of the whole study. After each trial participants have been asked, which supplement or placebo they think was in the drink or in the capsules. Fifty-six percent of the answers were correct indicating that supplement identification was purely random.
Dosage The athletes received a sodium citrate supplementation of 0.5 g per kg body mass or a placebo solution with 0.045 g sodium chloride per kg body mass. Both substances were dissolved in 700 ml tap water. The taste (salty) and color (clear) of the two drinks were identical. The gelatin capsules were filled with 6 mg caffeine per kg body mass or with the same amount of mannitol (placebo) and looked identical. The capsules were swallowed with a mouthful of tap water.
Blood Measurements Whole blood samples (95 μl) for blood analysis were taken from the earlobe before the ingestion of any supplement or placebo, before the warm up, after the warm up
and immediately after completion of the 1,500-m test. Whole blood samples (10 μl) to analyze lactate were taken from the earlobe before warm up, after warm up and every 2 min until 10 min after having completed the 1,500-m time trial. Due to technical difficulties in the four trials of one participant, we weren`t able to capture blood samples for blood analysis. The blood lactate concentration was analyzed enzymatically (Super GL Ambulance, Ruhrtal Labor Technik, Möhnesee, Germany). Blood pH (precision 0.07% CV [coefficient of variation]), bicarbonate and sodium concentrations (precision 0.4% CV) were analyzed with a blood analyzer (I-Stat, Abbott, Abbott Park, Illinois, USA).
Gastrointestinal Sensations Gastrointestinal tolerance was recorded before ingestion of the supplements, before warm up, after warm up and after completion of the 1,500-m trial.
Statistics The QQ-plot and the histogram showed that the data were not normally distributed. Therefore, results were presented as median (minimum; maximum) and a nonparametric statistical analysis was performed using the Friedman test. If significant results were identified with the Friedman test, a Wilcoxon post hoc-test was employed to localize the differences between the four treatments. The values were considered to be significantly different if p < .05. For the statistical analysis, IBM SPSS version 20.0 (IBM, Somers, New York, USA) was used.
Results Caffeine and sodium citrate supplementation as well as the combination showed no significant effect on the time to complete the 1,500-m wheelchair trial compared with placebo (Figure 2). To analyze time to complete
Caffeine and Sodium Citrate Supplementation in SCI 299
Figure 2 — The time to complete the 1,500-m wheelchair-racing trial for the four different treatments. Note that there were no significant differences between the four treatments.
1,500 m all of our data were included in the Friedman Test, even if some data points are illustrated as outliers in the box plot. Figure 3 shows the individual effects of the interventions on the 1,500-m time trial performance compared with placebo. The data of the blood analysis (pH, bicarbonate and sodium concentrations) are shown in Table 2. Compared with placebo and caffeine ingestion, blood pH, bicarbonate and sodium concentrations before the 1,500-m trial were significantly higher after the sodium citrate and combination treatment. In addition, the bicarbonate concentration after the 1,500-m trial was also significantly higher after the sodium citrate and combination treatment compared with placebo and caffeine. Furthermore, caffeine and the supplement combination resulted in a significant increase in maximal lactate concentrations compared with placebo (Figure 4). Finally, the maximal lactate concentrations after the combination treatment were significantly higher compared with sodium citrate alone. The maximal lactate concentrations in the sodium citrate trial tended to be higher compared with placebo (p = .051). Five out of nine athletes suffered from gastrointestinal side effects (nausea, illness and diarrhea) after the
ingestion of sodium citrate or the combination of both supplements. However, no trial had to be cancelled due to the side effects. Resting (p = .134), average (p = .364) and maximal heart rate (p = .191) was not significantly different between the four test interventions. Time to complete 1,500-m did not depend on trial order (p = .269) and did not show any significant improvement between the first and the last trial (p = .214; Figure 5).
Discussion The main finding of this study was that neither caffeine nor sodium citrate supplementation nor the combination of the two supplements had an effect on the 1,500-m time trial performance in elite wheelchair-racing athletes compared with the placebo treatment (Figure 2). However, the maximal blood lactate concentrations, blood pH, sodium and bicarbonate concentrations showed significant differences compared with placebo (Figure 4 and Table 2). Thus, sodium citrate is absorbed by the gastrointestinal tract of spinal cord injured individuals resulting in a higher blood pH and bicarbonate concentration. Consequently,
Figure 3 — The time differences to complete the 1,500 m between placebo and the three other interventions, + = faster time to complete the trial compared with placebo,— = slower time to complete the trial compared with placebo
Figure 4 — The maximal blood lactate concentrations compared between the four different treatments. * p < .05; ** p < .01 300
Table 2 Blood Parameters Measured Before the Supplementation (Baseline), Before (Pre), and After (Post) the 1,500-m Wheelchair Racing Time Trial (n = 8) Parameter Blood pH
Baseline
Pre 1,500-m
Post 1,500-m
placebo
7.417 (7.397; 7.441)
7.427 (7.387; 7.576)
7.268 (7.199; 7.419)
caffeine
7.444 (7.364; 7.489)
7.451 (7.416; 7.512)
7.248 (7.166; 7.450)
sodium citrate
7.451 (7.388; 7.475)
7.527 (7.450; 7.585)*§
7.393 (7.278; 7.562)
combination
7.429 (7.390; 7.486)
7.516 (7.466; 7.576)*§
7.352 (7.285; 7.489)
27.0 (21.1; 28.7)
15.2 (10.8; 21.2)
[HCO3-]
placebo
27.8 (21.1; 29.9)
(mmol∙l-1)
caffeine
26.2 (20.7; 29.3)
25.8 (17.7; 29.1)
13.3 (10.0; 21.8)
sodium citrate
27.4 (21.5; 35.0)
30.6 (28.3; 37.6)*§
21.7 (16.0; 35.6)*§
combination
26.7 (21.9; 30.7)
32.3 (25.8; 34.6)*§
20.2 (14.8; 25.4)*§
[Na+]
placebo
135 (130; 136)
138 (131; 140)
140 (132; 142)
(mmol∙l-1)
caffeine
134 (132; 136)
137 (133; 139)
139 (135; 142)
sodium citrate
134 (130; 140)
140 (137; 142)*§
141 (138; 145)§
combination
136 (130; 139)
139 (136; 140)§±
140 (135; 142)§
*Significant (p
