Author(s): YAMAMOTO, T., MATSUMURA, T., YUUKI, I.W., AMAKO, Y., TACHI, K., HASHIMOTO, K., DORA, K., ISAKA, T., HASHIMOTO, T., Institution: RITSUMEIKAN UNIVERSITY, Country: JAPAN, Abstract-ID: 2056

INTRODUCTION:
World Athletics recommends caffeine (CAF) and creatine (CRE) as effective ergogenic aids for track and field (1), and actually both improve sprint running performance (2,3). However, many laboratory-based studies provide inconsistent evidence for the combined effects of CAF and CRE on athletic performance, e.g., additive, nonadditive, or antagonistic (4-6). It has been suggested that CAF and CRE exert antagonistic effects on intramuscular Ca2+ dynamics (7). Given that, however, CAF only directly affects muscle contractility at supraphysiological concentrations (8), and may exert its ergogenic effects via central mechanisms (e.g., adenosine receptor antagonism), CAF and CRE may not compete and could provide additive effects on sprint performance. More importantly, no study has directly examined their combined effects on sprint running performance in track and field events. Therefore, we directly tested the combined effects of CAF and CRE on sprint running performance using a field test.
METHODS:
This double-blind randomized controlled trial employed a combination of parallel (CRE vs. placebo [PLcre]) and crossover (CAF vs. placebo [PLcaf]) designs. Thirty-two male track and field athletes were randomly allocated to a CRE group (n=15; 20±2 yrs; personal best 100-m sprint time: 11.07±0.39 s) or a PLcre group (n=17; 20±1 yrs; personal best 100-m sprint time: 11.04±0.24 s). The CRE group completed a 7-day loading phase (20 g/day), while the PLcre group followed an identical protocol with placebo. After the loading phase, participants performed 60-m sprint trials under both CAF (6 mg/kg) and PLcaf conditions in a counterbalanced manner, yielding four conditions (CRE+CAF, CRE+PLcaf, PLcre+CAF, PLcre+PLcaf). The 60-m sprint was performed indoors on all-weather track surface, and sprint time and velocity were calculated from the displacement data obtained using a laser system. We applied a linear mixed-effects model and Type III analysis of variance (ANOVA) to detect combined or main effects of CAF and CRE.
RESULTS:
No significant interaction between caffeine and creatine was observed for 60-m sprint time (P=0.867). There was a significant main effect of caffeine with faster sprint time with CAF than PLcaf (estimated difference: -0.10 s; P<0.001), whereas a main effect of creatine was not significant (estimated difference: -0.03 s, P=0.340).
CONCLUSION:
Acute caffeine ingestion improves sprint performance in male track and field athletes, and this benefit is not modified by creatine loading, either additively or antagonistically. This is the first study to provide direct evidence of the practical use of caffeine to enhance sprint running performance in track and field, independent of creatine supplementation strategy.

REFRENCES:
1. Burke et al. (2019) 2. Matsumura et al. (2023) 3. Skare et al. (2001) 4. Vandenberghe et al. (1996) 5. Lee et al. (2011) 6. Marinho et al. (2023) 7. Trexler & Smith-Ryan. (2015) 8. Neyroud et al. (2019)