Document Type : Research Paper
Authors
1
MSc, Department of Physical Education, Raja University, Qazvin, Iran
2
PhD of Exercise Physiology, Department of Physical Education and Sports Sciences, Faculty of Social Sciences, Raja University, Qazvin, Iran
3
Assistant Professor, Department of Sport Sciences, Faculty of Social Sciences, Raja University, Qazvin, Iran
Abstract
Extended Abstract
Background and Purpose
This study aimed to investigate the acute effects of different doses of caffeine, citrulline malate, and post-activation potentiation (PAP) on lower limb power, anaerobic capacity, and aerobic performance in female kickboxers. Caffeine is a well-known ergogenic aid that enhances performance by increasing calcium release in muscle fibers and reducing the perception of effort. Citrulline malate enhances blood flow and nutrient delivery via increased nitric oxide production. PAP, characterized by a prior muscle contraction enhancing subsequent explosive performance, has demonstrated efficacy in improving power output. However, the combined effects of these interventions, especially among female athletes, remain underexplored. This study aimed to address this gap by examining how these supplements—used alone or in combination with PAP—influence key performance metrics including vertical jump height, anaerobic power, and maximal oxygen consumption (VO₂max) in female kickboxers. The findings offer valuable insights for athletes and coaches pursuing optimized, evidence-based supplementation and training regimens.
Materials and Methods
Seventy female kickboxers aged 15–25 years with at least two years of training experience were randomly assigned to one of seven groups: control (Con), caffeine 4 mg/kg (Caf4), caffeine 5 mg/kg (Caf5), caffeine 4 mg/kg plus citrulline malate (Caf4+CitMal), caffeine 5 mg/kg plus citrulline malate (Caf5+CitMal), caffeine 4 mg/kg plus citrulline malate and PAP (Caf4+CitMal+PAP), and caffeine 5 mg/kg plus citrulline malate and PAP (Caf5+CitMal+PAP). Participants abstained from caffeine, citrulline, and other supplements 24 hours before testing.After a standardized warm-up, participants received their assigned supplementation. PAP was induced 10 minutes prior to performance testing, using plyometric exercises such as squat jumps. Explosive power was assessed via maximal vertical jump height. Anaerobic power was calculated from six 35-m sprints performed with 10-second rest intervals. Aerobic capacity was assessed by an incremental shuttle run between two 20-m lines, continued until volitional exhaustion. VO₂max was estimated using the formula described by Matusiński et al. (2021).Data were analyzed using one-way ANOVA and Tukey’s post hoc tests. Statistical significance was set at p < 0.05. Ethical approval was granted by the Ethics Committee of Qazvin University of Medical Sciences (IR.QUMS.REC.1403.033). All participants gave written informed consent.
Results
Significant improvements in performance were noted in several groups. The combination group receiving caffeine 5 mg/kg with citrulline malate and PAP (Caf5+CitMal+PAP) exhibited the most substantial gains: a 12% increase in vertical jump height and a 15% improvement in anaerobic power compared to controls (p < 0.05). By contrast, caffeine at 4 mg/kg alone (Caf4) showed no significant performance benefit, indicating a dose-dependent effect. Regarding aerobic performance, caffeine combined with citrulline malate (Caf4+CitMal and Caf5+CitMal) significantly enhanced VO₂max, with the higher dose (Caf5+CitMal) producing a 10% increase compared to controls (p < 0.05). The addition of PAP did not further enhance VO₂max, suggesting PAP's effects are likely confined to short-duration explosive movements.The Caf4+CitMal+PAP group showed significant, but less pronounced, improvements in vertical jump height (+8%) and anaerobic power (+10%) than the Caf5+CitMal+PAP group (p < 0.05). Control and Caf4 groups did not demonstrate significant changes in any performance metric.These ergogenic effects may be mechanistically explained by caffeine’s capacity to augment calcium release and reduce central fatigue, while citrulline malate facilitates nitric oxide-mediated vasodilation and nutrient delivery, attenuating muscle fatigue and damage. PAP’s enhancement of neuromuscular efficiency appears to synergize with these effects selectively in explosive activities.
Conclusion
This study demonstrates that combining caffeine at 5 mg/kg with citrulline malate supplementation and PAP markedly improves lower limb power, anaerobic capacity, and aerobic performance in female kickboxers. Caffeine at the lower dose of 4 mg/kg does not confer significant benefits. Further, PAP predominantly enhances explosive and anaerobic performance rather than aerobic capacity.Practically, these findings highlight the importance of appropriate dosing and combination strategies when using supplements and conditioning protocols to boost athletic performance. Coaches and athletes should consider integrating higher caffeine doses alongside citrulline malate and PAP to maximize explosive power gains.Future research should explore longer-term supplementation effects, dose-responses across different populations, and whether similar synergistic effects appear in other sports disciplines.
Key Words: Caffeine, Citrulline Malate, Post-Activation Potentiation, Anaerobic Power, Aerobic Capacity, Vertical Jump, VO₂max
Article Message
This investigation reveals that caffeine, citrulline malate, and PAP interact synergistically to enhance athletic performance. Optimal ergogenic benefits occur with caffeine administered at 5 mg/kg, especially when combined with citrulline malate and PAP. Athletes and coaches can leverage these insights to design evidence-based supplementation and training programs. The findings underscore the necessity of tailoring caffeine dosing for maximal efficacy.
Ethical Considerations
The study adhered to the ethical protocols of Qazvin University of Medical Sciences (IR.QUMS.REC.1403.033). Written informed consent was obtained from all participants, with confidentiality and safety ensured throughout.
Authors’ Contributions
All authors contributed equally to study conception, data analysis, interpretation, and manuscript drafting.
Conflict of Interest
The authors declare no conflict of interest.
Acknowledgments
The authors thank all participants for their cooperation and the staff at Raja University for their invaluable support. Special thanks to the Ethics Committee of Qazvin University of Medical Sciences for their oversight and guidance.
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