Effects of creatine supplementation on multiple 40m sprint performance ABSTRACT Purpose: To examine the effects of creatine supplementation on multiple sprint performance. Methods: Seven (n = 3 Creatine, n = 4 Placebo) male & female University of Chichester sports students were used (Mass (kg) , Age (yrs) ). All subjects participated in 6 x 40m sprint separated by 25seconds. Results: The ANOVA analyses revealed that there was no significant main effect of time, group or interaction in mean sprint time (s), HR (bminˉ¹) or mass (kg). Conclusion: This study suggests that creatine monohydrate supplementation conveys no benefit to multiple sprint running performance. INTRODUCTION Intramuscular phosphocreatine (PCr) acts as a short term energy buffer to maintain a rapid rate of adenoine triphosphate (ATP) during short brief periods of high-intensity (HIE) exercise < 10 seconds (Glaister et al., 2006). It’s been suggested that increasing creatine (CR) content of muscle may increase availability of PCr, therefore allowing enhanced ATP resynthesis (Ahmun, Tong & Grimshaw, 2005). CR supplementation is reported to increase CR content of muscles by ~ 20% (Spencer, Bishop, Dawson & Goodman, 2005). Other functions of PCr metabolism are the buffering of hydrogen ions produced during anaerobic glycolysis and the transport of ATP (Burke & Deakin, 2006).Previous studies have found CR supplementation can elevate total CR in muscle by 20-50% leading to increases in PCr accounting for 20-40% of difference which led to improvements in muscular force and power outputs (Harris, Soderlund & Hultman, 1992; Balsom et al., 1993). In contrast other studies have found no significant effects of creatine supplementation (Smart et al., 1998; Glaister et al., 2006). In light of this previous research the aim of this study will be to look at the effects of creatine supplementation on sprint performance during 6 x 40m sprints with 25 second rests between sprints. METHODS Subjects - A convenience sample of 10 adult University sports students. However 3 students dropped out through injury & illness so only 7 fully participated (Table 1). They gave informed consent prior to participation in accordance with the local ethics committee. Supplementation - Subjects were given oral supplements over 5 days, either creatine-monohydrate (CR group n= 3) or a placebo (PL group n= 4). Both groups received 20 g (4 packages, each containing 5 g) of either creatine monohydrate or a placebo which was taken 4 x daily with a warm juice drink during a 5 day loading phase. 40m Sprint – After a specific warm-up subjects performed six maximal 40 m sprints separated by 25second rest. Light gates with electronic timing (Fushion Sport © ) were used to collect time (Figure 1). Statistical Analysis Data was analysed using a two-way repeated measures ANOVA via an SPSS (version 16.0, SPSS, Inc., Chicago, IL.) computer package. Significance levels were set at p = FACULTY OF SPORT, EDUCATION & SOCIAL SCIENCES RESULTS Normality tests showed that all the data comes from a normally distributed population. The 2-way repeated measures ANOVA analyses revealed that for mean sprint time (s) there was no main effect for group (f (1, 6) = 0.08, p = 0.93), or for time (f (1, 6) = 0.56, p = 0.49) and there was no interaction effect (f (1, 6) = 1.42, p = 0.29). The analyses also revealed that for mean HR (bminˉ¹) there was no effect for time (f (1, 5) = 0.737, p = 0.430), group (f (1, 5) = 1.031, p = 0.357) or interaction effect (f (1, 6) = 6.003, p = 0.058). Mass (kg) was also unaffected, group (f (1, 5) = 8.815, p = 0.31), time (f (1, 5) = 0.78, p = 0.62) & interaction effect (f (1, 5) = 8.815, p = 0.31) (Table 2). CONCLUSIONS The main findings of this study were that creatine supplementation had no significant effect on measures of fastest time, mean time, fatigue or heart rate (Table 2). This study supports the findings of previous research which concluded that creatine supplementation may offer no benefit to multiple sprint performance (Glaister et al., 2006). This is in disagreement with previous studies that showed significant results with creatine supplementation (Harris, Soderlund & Hultman, 1992; Balsom et al., 1993). The most likely reasons for the findings in this study are that there was a wide range of training status between subjects, the experimental design became compromised due to differing weather conditions in pre & post testing and the increase of muscle PCr after CR supplementation may not have been enough to enhance multiple sprint performance. Although statistical significance was not achieved for any of the measured parameters, there were small improvements in performance in one of the creatine group subjects. This subject was trained and plays a high standard of competitive football therefore training status could be an important factor in responding to creatine supplementation. An interesting finding was that the only trained subject in the placebo group also increased sprint performance after supplementation (Figure 3). Research has shown that as much as 20-30% of subjects either respond minimally or not at all to CR loading (Harris et al., 1992). Although muscle PCr was not measured directly, the increase in weight in the CR group was consistent with that reported in previous research and was most likely fluid (Branch, 2003). This may be due to muscle, via an insulin-stimulated and sodium-dependant transporter, taking up CR. This process generates active sodium and amino acid gradient across the plasma membrane which draws water into the cell (Mihic, MacDougall, McKenzie & Tarnopolsky, 2000). This study suggests that creatine monohydrate supplementation conveys no benefit to multiple sprint running performance although further research into effect of training status on supplementation is warranted. KEY REFERENCES Glaister, M., Lockey, RA., Abraham, CS, & Staerck, A. (2006) Creatine supplementation and multiple sprint performance. Journal of Strength and Conditioning Research, 20, (2), Harris, RC., Soderlund, K, & Hultman, E. (1992) Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation, Journal of Applied Physiology, 83, Figure 1 Experimental layout of the 40m multiple sprint NumberMass (kg)Age (yrs)Height (cm) Subjects Table 1 Subject baseline characteristics Variable Group Pre Post MeanSD +MeanSD + Mass (kg)CR PL HR (BPM)CR PL m Total time (s)CR m Total time (s)PL Table 2 Means & SD + results for the sprint times 1m 40m Figure 3 Individual mean sprint times (s) in both groups