Athletes are consistently looking to find an edge over competitors and improve their personal performance. A study by the IAAF found that 82% of 400 metres athletes questioned were using additional dietary supplements, so accurate research is very important (Maughan et al., 2007). Athletic performance can be affected by muscular fatigue as the required power output of a muscle is no longer being achieved (Fitts 1994; Spangenburg et al., 1998). One of the mechanisms put forward for fatigue occurring in muscle is due to acidosis (Jones et al., 1977; Verbitsky et al., 1997) although the majority of this research was conducted before the affects of inorganic phosphate where known or considered (Phillips et al. 1993). Inorganic phosphates increases during exercise, this increase prevents the required cross bridges being available for higher intensity exercise, thus reducing force production (Westerblad et al. 2002).
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Linderman, (1991) explains how during anaerobic exercise, lactic acid is produced faster than it can be removed by muscle tissue. Because of this, a decrease in pH levels occurs called acidosis , increasing H+ concentration, and thus affecting energy systems . Sodium bicarbonate (NaHCO3) ingestion prior to performance has been shown to affect the onset of fatigue, which has been put down to enhancements in endogenous H+ buffering capacity (Horswill, 1988). NaHCO3 ingestion acts as an alkalising substance, increasing pH levels before exercise, potentially delaying acidosis (McNaughton, 1992). A more recent study by Robergs et al. (2004), explains how this acidosis theory might not be relevant due to lactate being unable to release protons. Exercise duration of 60 to 240 seconds, seems to be affected by NaHCO3 performance (McNaughton, 1992, McNaughton et al., 1999; McNaughton and Thompson, 2001), but much of this research has been completed in a laboratory on a cycle ergonometre. The 400 metres, is an event that induces high levels of acidosis, recently a relationship between increased acidosis and an decrease in athletes running velocity, particularly over the last 100 metres has been seen (Hanon et al., 2010).
The correlation noted by Hanon et al. (2010) and the enhancements in accessible technology, has lead to the development of this research study, with its purpose to test the hypothesis that NaHCO3 supplementation can affect athlete performance times in the 400 metre event, and delay the fatiguing effects of acidosis over the final fatigue affected 100 metres.
A group of 8 male and 1 female healthy junior elite athletes, from 1500 metre, 500 metre and cross country athletic disciplines took part in the study. The participants characteristics were, (Mean ± SD) age 19.3 ± 1.3 years, mass 63.2 ± 6.1 kg. The study was ethically approved by the university’s ethics committee and all participants completed and signed informed consents forms after being explained the full study.
Familiarisation commenced 48 hours before testing and involved running the 400 metre flat out with a 2 metre rolling start, an overall 400 metre time and 100 metre split times were measured for baseline analysis.
The study used a blind cross over design, with each participant testing twice, once with NaHCO3 supplementation and once with a placebo. As similar studies has used, (Hunter et al., 2009) 300g per kg of bodyweight of NaHCO3 for each participant was used, mixed with 750ml of water and an unfamiliar tasting cordial , a placebo of 750ml of water and cordial was used and a further 250ml of water was available for athletes. A warm up of 800 metres jogging and stretching was implemented. Each participant was required to run a 400 metres sprint as quickly as possible, with a 2 metre rolling start. An overall time and 100 metre split times were recorded using light gates positioned at each 100 metres and the start/finish line on a UK athletic certified track. A washout period of 48 hours was used between tests.
The statistics software, SPSS for Windows (Chicargo, IL) was used to compare the overall performance times in each of the 3 trails, a repeated measure ANOVA test was used, this was followed up by a Pairwise Comparison (Bonferroni) test, to check for type 1 errors. Paired t-tests were then used to assess difference between conditions over the last two 100 metre split time. A significant statistical value of P ≤ 0.05 was set.
The ANOVA, found no significant difference (P = 0.135) between, baseline testing, placebo conditions and NaHCO3 supplementations affect on 400 metre performance. Post hoc Bonferroni) tests revealed although no significant differences between sodium bicarbonate vs. placebo (P = 0.100) and sodium bicarbonate vs. baseline testing (P =0.299), supporting the ANOVA findings. A significant difference in 400 metre time was seen in the baseline vs. placebo test (P = 0.027).
The paired samples t-test comparing time from first split to the finish between Sodium Bicarbonate and placebo trials, found no significant difference, reporting a P value of 0.499. A non significant P value of 0.319 was found when the t- test tested increases in time from 200 metres to 300 metres between the sodium bicarbonate trails and the placebo trial. Comparing the difference in slow down over the 300 metre to 400 metre split, the paired sample t test showed a significant difference, with the P value being 0.042 when the sodium bicarbonate trail and placebo trials were analysed. Showing during the sodium trial, athletes slowed less when compared with the placebo trail.
The main purpose of this study was to determine whether NaHCO3 ingestion prior to anaerobic exercise, delayed acidosis and enhanced performance over 400 metres. The results of the ANOVA revealed there were no significant differences (P = 0.135) between the baseline, placebo and NaHCO3 conditions. After completion of the Pairwise Comparison, a significant difference (P= 0.027) was seen, when the baseline and placebo tests where compared. This result could be down to the placebo affect discussed by Beedie and Foad (2009), it is a psychological phenomenon, dependant on participant expectations.
NaHCO3 ingestion did not significantly improve performance times over 400 metres, a P value of 0.100 from the pairwise comparison, confirms this when the placebo and NaHCO3 supplementation conditions are compared. Concurrently, Tiryaki and Atterborn (1995), found NaHCO3 did induce alkalosis but it had no significant effect on performance. This may add weight to the argument by Westerblad et al. (2002) who explain inorganic phosphates affecting fatigue rather than lactic acid. These findings are not concurrent with many other research studies who found NaHCO3 ingestion prior to intense exercise, enhanced performance (Hunter et al., 2009; Hanon et al., 2010), Figure 1. Below shows how although not significant, some difference was seen between the mean values, leading to the requirement of further data analysis of the 100 metre split times.
The last 100 metres of the 400 metres sprint, is the point at which fatigue is most likely going to affect performance due to acidosis (Hanon et al. 2010). The significant difference in performance times seen when NaHCO3 ingestion and placebo were compared (Figure 2.), supports past findings by Goldfitch et al. in 1988, who found 400 metre racing times enhanced when NaHCO3 was ingested prior to performance. This could be because, induced alkalosis which increases the muscle fibre conduction velocity, which consequently through the rate of force decline being reduced enhances the working muscle fatigue resistance.
The significant P = 0.042 value, was unanticipated as overall times were not significantly reduced after NaHCO3 ingestion. This result could be evidence to show NaHCO3 supplementation might be better suited to longer distance sporting disciplines. A study by McNaughton and Cedaro (1991), supports the idea of NaHCO3 ingestion induce alkalosis, finding more metres rowed during 360 seconds of work, there are concurrent finding from McNaughton and Thompson (2001) found more work completed in the alkalinizing agent data was compared with a placebo data. This finding goes someway to supporting use of NaHCO3 prior to anaerobic exercise.
In summary, NaHCO3 supplementation may have some affect of performance. The affect may be more prevalent and advantageous in longer durations of exercise, as it may be that the body’s natural H+ buffer mechanisms can deal with exercise induced acidosis during short durations. Future studies in this area should consider using larger participation groups as a limitation of the study was limited participation numbers, which did not give an accurate representation of population. Research should concentrate on finding the point where buffering systems can no longer naturally handle the accumulation of H+, and fatigue begin to occur due to this. NaHCO3 affect at this point and beyond can then be further researched. Future studies can then determine what types and length of exercise the alkalinising agents might affect, so supplementation could be used in a practical setting.
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