Performance-enhancing effects of caffeine and L-Theanine among Iranian elite wrestlers: a focus on cognitive and specific physical performance

ABSTRACT

Background

Caffeine is a well-known ergogenic aid that can enhance physical and cognitive performance. However, it often induces side effects, such as anxiety and overstimulation, which can be problematic in high-pressure sports like wrestling. L-theanine, a non-stimulant amino acid found in tea, may help mitigate these effects by promoting a calm yet focused mental state. This study aimed to investigate the acute effects of caffeine, L-theanine, and their combination on physical performance, cognitive function, and anxiety in elite male wrestlers.

Methods

In a double-blind, placebo-controlled, crossover design, 12 elite male wrestlers (21.8 ± 2.1 years) completed four test sessions under randomized conditions: placebo (PLA), caffeine (CAF; 3 mg/kg), L-theanine (THE; 3 mg/kg), and caffeine + L-theanine (CAF+THE; 3 mg/kg each). After 60 minutes, athletes performed the wall-squat test, vertical jump height (VJH), medicine ball throw (MBT), handgrip strength, and the Specific Wrestling Fitness Test (SWFT). Cognitive function was assessed pre- and post-SWFT using a computerized Stroop test. Anxiety was assessed using the State-Trait Anxiety Inventory (STAI), and side effects were recorded.

Results

CAF+THE outperformed PLA in wall-squat time (p = 0.001), MBT (p = 0.005), VJH (p = 0.011), and grip strength (p = 0.004). SWFT throw count was highest in CAF+THE versus all other conditions (p < 0.001). Post-SWFT Stroop reaction time was faster in CAF+THE than PLA (p = 0.004) and THE (p = 0.036), and accuracy was also higher (p = 0.009 vs PLA). CAF alone increased state anxiety compared to PLA (p = 0.021), while CAF+THE reduced anxiety to below placebo levels (8% incidence vs 33%). Trait anxiety was lower in CAF+THE compared to CAF (p = 0.018). The prevalence of caffeine-induced tachycardia (92%) was notably reduced under CAF+THE (17%).

Conclusion

CAF+THE (3 mg/kg each) enhances elite wrestlers’ strength, endurance, cognitive speed, and accuracy while reducing anxiety and physiological side effects commonly associated with caffeine alone. This combination represents a safe, practical supplement strategy for combat sports athletes who must maintain explosive performance and mental control under stress. Coaches are encouraged to trial CAF+THE protocols during training to personalize timing and dosage.

1. Introduction

Wrestling is an Olympic combat sport that demands exceptional physical prowess and cognitive acuity from its athletes. Elite wrestlers engage in high-intensity bouts that tax their strength, anaerobic power, and strategic thinking, often competing in multiple matches on a single day and recovering with as little as 30 minutes to a few hours between bouts [1–3]. These rapid turnarounds and the intense pressure of competition place heavy stress on both the body and mind, driving a continuous search for nutritional strategies to accelerate recovery and enhance performance [1,2]. In this context, ergogenic aids that can bolster dual-domain performance – supporting both physical output and cognitive function – have garnered growing interest.

Caffeine (1,3,7-trimethylxanthine) is one of the most widely consumed ergogenic aids in sport, used by up to 76% of elite athletes before competition [4]. Since its removal from the World Anti-Doping Agency’s banned list in 2004, its prevalence has increased markedly, supported by a broad base of evidence demonstrating performance-enhancing effects across endurance, strength, and high-intensity activities [4,5]. Acute caffeine ingestion, typically within the range of 3–9 mg/kg body mass about 60 minutes pre-exercise, enhances fat oxidation, spares glycogen, and stimulates the central nervous system, thereby delaying fatigue and improving overall performance [4,6]. In high-intensity, anaerobic efforts relevant to combat sports, caffeine has also been shown to increase repeated-sprint capacity and neuromuscular output [4,6]. Notably, recent findings by Saremi et al. (2025) demonstrated that even a low dose of 3 mg/kg caffeine significantly improved time to exhaustion, explosive power, and reduced perceived muscle soreness in professional kickboxers, reinforcing its value as a practical ergogenic aid in combat scenarios [7]. However, other investigations utilizing multiple dosage protocols – such as 3, 6, and 9 mg/kg – indicate a potential dose-dependent performance enhancement. For example, Durkalec-Michalski et al. (2019) reported that higher caffeine doses yielded more pronounced improvements in judo-specific fitness and training activity, suggesting athletes engaged in explosive, intermittent sports may benefit from higher intakes [8]. These findings collectively support a nuanced, individualized approach to caffeine dosing, acknowledging that both low and high doses can be effective depending on sport-specific demands and athlete sensitivity. In addition to physical benefits, caffeine reliably enhances cognitive performance, including reaction time and alertness – attributes critical for athletes operating under high-pressure, time-sensitive conditions [4].

In parallel, L-theanine (γ-glutamylethylamide) has emerged as a supplement of interest for its unique neurocognitive properties. L-theanine is a naturally occurring amino acid in green tea leaves, known for promoting relaxation without sedation and reducing stress and anxiety levels [9–12]. Mechanistically, L-theanine increases brain levels of neurotransmitters like serotonin, dopamine, and GABA, and it stimulates alpha-wave brain activity associated with a calm yet alert mental state [10,12]. These effects can translate into improved concentration, sharper focus, and better mood regulation under stress [9–12]. Importantly for athletes, L-theanine supplementation has been shown to attenuate stress hormones, such as cortisol and adrenaline, during challenging tasks [11,12], which may help buffer stress-related performance decrements and enhance endurance capacity under fatigue [9,10]. While research on L-theanine in exercise settings is still emerging, early studies suggest potential benefits for immune function in athletes and stress reduction during intense training [11,13]. In a randomized, double-blind, placebo-controlled study, healthy adult participants (n = 48) received 250 mg of caffeine (~3.5 mg/kg), 200 mg of L-theanine (~3 mg/kg), both, or neither. Caffeine increased alertness, anxiety, and blood pressure, while L-theanine reduced overall reaction time on a visual probe task [14]. This 200 mg dose (~3 mg/kg for a 65–70 kg individual) aligns with commonly used dosages in previous research evaluating L-theanine’s acute cognitive effects, providing rationale for the 3 mg/kg dose used in the present study. The cognitive support provided by L-theanine, including improved attention and anxiety management, suggests it could complement physical training by bolstering the mental resilience and focus required in combat sports. However, literature on L-theanine’s direct effect on sport performance remains limited and sometimes inconsistent [9,10].

Increasingly, attention has turned to the combination of caffeine with L-theanine as a dual-action ergogenic strategy. The rationale is that L-theanine’s calming, nootropic effects may synergize with caffeine’s stimulatory benefits, thereby enhancing cognitive performance while mitigating side effects such as jitters or anxiety [15–17]. In non-athlete populations, co-ingestion of caffeine and L-theanine has indeed been shown to improve attention, accuracy, and alertness more than either compound alone [9,16]. Recent sports science findings extend this synergy to athletic settings. For example, a 2023 study in elite curling athletes reported that combining 6 mg/kg caffeine with 6 mg/kg L-theanine led to superior results in both cognitive tests (Stroop reaction time and accuracy) and skill-specific performance (target shooting accuracy) compared to either supplement alone [15]. Similarly, other precision- and endurance-based sport contexts have reported improved attention and reduced anxiety with this combination, supporting its potential across different athletic populations [9,17]. This suggests that the caffeine+L-theanine pairing can concurrently enhance mental processing and execution of sport-specific skills. The concept of multi-ingredient supplementation yielding multifaceted performance gains is further supported by analogous research in combat sports. For example, co-supplementation of caffeine with taurine in elite boxers significantly enhanced agility, balance, and cognitive reaction time, outperforming the effects of either supplement in isolation [18]. Such evidence highlights a broader trend in sports nutrition toward ergogenic combinations that target both physiological and psychological aspects of performance.

Despite growing interest in ergogenic aids that target both physical and cognitive domains, a notable gap remains in the literature regarding the co-supplementation of caffeine and L-theanine in combat sports such as wrestling. While a substantial body of research has explored caffeine’s effects in disciplines such as boxing, karate, and mixed martial arts, elite wrestlers remain an understudied population, particularly in terms of cognitive outcomes under supplementation [1,2,4]. Wrestling is uniquely demanding, requiring high levels of anaerobic capacity, muscular strength, and tactical precision under fatigue, making it an ideal setting for testing dual-domain interventions. Although recent studies have demonstrated the physical and cognitive benefits of low-to-moderate caffeine dosing in combat athletes [7] and others have highlighted the anxiolytic and neurocognitive support offered by L-theanine [10,11,16,17], research examining their combined effects in wrestlers is virtually nonexistent. Given the intermittent intensity of wrestling matches, the brief recovery windows, and the psychological pressure of repeated competition, wrestlers may uniquely benefit from a supplementation strategy that enhances both neuromuscular output and mental performance resilience. Importantly, no study to date has directly assessed caffeine’s and L-theanine’s interactive effects on cognitive function and sport-specific performance metrics in elite wrestlers, representing a critical evidence gap.

Therefore, the present study aimed to investigate the acute effects of caffeine and L-theanine, administered individually and in combination, on cognitive performance (e.g. attention and reaction time) and physical performance (e.g. muscular endurance, explosive power, and wrestling-specific fitness) in elite Iranian male wrestlers. This research not only addresses a key limitation in the existing literature but also seeks to inform practical, evidence-based supplementation protocols to optimize athlete readiness and performance in high-stakes, fatigue-inducing competitive scenarios.

2. Methodology

2.1. Participants

Twelve elite male wrestlers (mean age: 17 ± 1 year) from Shiraz, Iran, who were active competitors in the Iranian National Wrestling League, volunteered to participate in this study. Participant anthropometric variables are presented in Table 1. Eligibility criteria included: (a) age ≥15 years, and (b) a minimum of three years of continuous experience as a competitive wrestler at the national level. Participants were excluded if they had: (a) consumed any ergogenic or hormonal substances (e.g. anabolic steroids, nutritional supplements) within the past three months; (b) used stimulants, narcotics, alcohol, or psychoactive drugs during the study period; (c) any diagnosed orthopedic, neurological, cardiovascular, pulmonary, or metabolic disorders that could impair physical performance; (d) any injury at the time of testing; or (e) known allergies to caffeine or green tea. All participants provided written informed consent prior to participation, and the test method, work conditions, and possible risks and injuries were explained to the participants. Caffeine allergy was ruled out, and no one reported using tobacco, alcohol, medications, or caffeinated beverages during the study. Habitual caffeine intake was assessed using the Caffeine Content Database provided by the Center for Science in the Public Interest (CSPI) [19], confirming that all participants were classified as low habitual caffeine consumers (≤70 mg/day). The present study complied with the Declaration of Helsinki and received approval from the Research Ethics Committees of the Faculty of Psychology and Educational Sciences, Shiraz University (approval code: IR.US.PSYEDU.REC.1403.053, 2024). To standardize physical activity, all participants trained in the same camp under a supervised, uniform training program. They were instructed to abstain from strenuous exercise for 48 hours before each testing session to minimize fatigue-related variability.

Table 1.

The anthropometric data of the participants (n = 12).

Characteristic	Mean ± SD
Age (years)	17 ± 1
Height (cm)	179.7 ± 8.2
Weight (kg)	70.9 ± 11.8
BMI (kg/m2)	21.85 ± 2.5

2.2. Sample size calculation and study design

The required sample size was determined using G*Power software (3.1.9.7) [20], based on a significance level of α = 0.05 (two-tailed) and a statistical power (1 − β) of 0.80. The calculation was informed by prior findings from a randomized controlled trial examining the effects of combined caffeine and L-theanine supplementation on reaction time, which reported a standardized effect size (Cohen’s d) of 0.653 for that outcome variable [15]. Based on these parameters, a minimum of 12 participants was deemed sufficient to detect statistically significant differences.

The present study employed a randomized, double-blind, placebo-controlled, crossover design (Figure 1). Before the experimental trials, all participants underwent a familiarization session where they were introduced to the testing procedures and protocols. To minimize external sources of stimulants, participants received a list of familiar dietary sources of caffeine and were instructed to abstain from consumption for 48 hours before each test session. During the initial assessment week, participants completed a Physical Activity Readiness Questionnaire (PAR-Q) and were screened for cardiovascular conditions reported within the last three months [21]. Baseline height, weight, and body mass index (BMI) measurements were also recorded. Participants were randomly assigned to one of four intervention conditions in a counterbalanced order: caffeine (CAF, 3 mg/kg), L-theanine (THE, 3 mg/kg), caffeine + L-theanine (CAF+THE), and placebo (PLA; maltodextrin) (Figure 2). Each supplement was administered in identical capsules to maintain blinding and was ingested with 250 mL of water. Following a 60-minute absorption period, participants completed the State-Trait Anxiety Inventory and the Stroop test (pre-Specific Wrestling Fitness Test (SWFT)), followed by assessments of wall squat endurance, medicine ball throwing distance, vertical jump height, and hand grip strength with five-minute intervals between. After a standardized 10-minute active recovery period (walking), the SWFT was conducted. Immediately post-exercise, the Stroop test was repeated to evaluate cognitive performance post-SWFT. A two-week washout was implemented between each experimental session to prevent carryover effects. All testing sessions were conducted under controlled environmental conditions, and participants were instructed to maintain consistent sleep, diet, and hydration routines throughout the study.

Figure 1.

The flowchart of the crossover supplementation design.

Figure 2.

Study design, supplementation, and testing protocol.

2.3. Supplementation protocol

All supplements and placebo doses were prepared and weighed using a high-precision analytical balance (AND GF-300, A&D Company, Tokyo, Japan) with a resolution of 0.001 g. Supplements were encapsulated in identical, opaque, size “00” gelatin capsules and stored in coded containers to maintain blinding. The placebo consisted of 400 mg of maltodextrin. The active conditions included CAF, THE alone, or a combined dose (CAF+THE) (Figure 2). Participants received 3 mg/kg body weight of either CAF, THE, or a combination of both in the mixed condition. All capsules were administered with 250 mL of water precisely 60 minutes before testing to coincide with the peak plasma levels for both compounds. The caffeine dosage was based on guidelines from the International Society of Sports Nutrition (ISSN), which recommends 3–6 mg/kg for improving strength, endurance, and cognitive performance [4]. The L-theanine dose reflects concentrations commonly found in brewed green tea and has been previously validated in clinical studies for reducing stress and enhancing attention without sedation [9,22].

A double-blind protocol was strictly followed. Capsules for all conditions (CAF, THE, CAF+THE, PLA) were identical in size, shape, color, and taste. An independent investigator not involved in data collection or analysis managed supplement coding and randomization. Neither the participants nor the researchers conducting the tests were aware of the treatment allocation at any point during the study. Blinding efficacy was maintained throughout all sessions, and participants were debriefed after completing the final trial.

2.4. Cognitive tests

2.4.1. State-Trait anxiety test

The 40-item State-Trait Anxiety Inventory (STAI) is a widely used psychological assessment tool that evaluates two dimensions of anxiety: state anxiety (SA) and trait anxiety (TA). It consists of 40 items, evenly divided between the two subscales. The first 20 items assess state anxiety, which reflects the respondent’s immediate feelings of apprehension, tension, and nervousness in response to a specific situation or stimulus. These items are rated on a four-point Likert scale ranging from 1 (“not at all”) to 4 (“very much so”). The remaining 20 items evaluate trait anxiety, which represents a more stable, enduring tendency to perceive a wide range of situations as threatening. Participants rate how frequently they experience such feelings using a similar four-point scale from 1 (“almost never”) to 4 (“almost always”). In both sections, total scores range from 20 to 80, with higher scores indicating greater anxiety levels. The STAI is particularly valuable in sports psychology for measuring athletes’ psychological responses under competitive stress or intervention conditions. In the context of this study, it was employed to examine the acute effects of caffeine and L-theanine – individually and in combination – on both situational and baseline anxiety among elite wrestlers [23].

2.4.2. Stroop Test

The Stroop test is a well-established neuropsychological assessment that evaluates cognitive control and selective attention, primarily reflecting frontal lobe activity [24]. The central phenomenon, known as the “Stroop interference effect,” refers to the increased time required to name the color of ink when it conflicts with the semantic meaning of a word, as compared to reading congruent or neutral stimuli. The test in this study consisted of three stimulus conditions: neutral, congruent, and incongruent. It included 30 neutral stimuli, where participants were asked to report the perceived color. Additionally, two blocks of 30 items each were administered. In the first block, participants identified the meaning of the word presented. In contrast, they responded to the ink color in the second block using designated directional keys corresponding to specific colors. The Stroop task was conducted twice – once before the SWFT (pretest) and once after the SWFT (posttest). Two primary outcomes were recorded: reaction time (RT) and the correct answer percentage (CAP), reflecting cognitive speed and accuracy under physical exertion.

2.5. Functional tests

2.5.1. Wall-squat test

The wall-squat test was used to evaluate lower-body muscle endurance. The correct posture was sitting, shoulder width straight and attached to the wall, knees at 90 degrees, shoulders to the wall, and arms hanging straight down. For this test, the maximum time to exhaustion was defined as the time interval from the task’s start until any of these positions could not be maintained. Participants must do their best to keep the correct position throughout the test while receiving no verbal encouragement [25–27]. It targets major lower-body muscle groups, including the quadriceps, hamstrings, and gluteal muscles, which are essential for wrestling-specific activities such as resisting takedowns, executing holds, and maintaining balance during high-intensity exchanges [3]. The wall-squat test also provides a meaningful index of isometric muscular endurance, a capacity critical for maintaining lower-body stability during repeated, sustained efforts typical of wrestling competition [1]. To enhance measurement consistency, standardized test protocols and familiarization sessions were conducted prior to data collection.

2.5.2. Backward overhead medicine ball throw test

The Standing Backward Overhead Medicine Ball Throw (MBT) test assessed upper-body and total-body explosive power, a key physical attribute in wrestling for performing throws, lifts, and explosive transitions. Participants stood at a marked line, feet shoulder-width apart, facing away from the throwing direction. Holding the medicine ball with both hands, they swung it backward over their head and released it explosively behind them. A slight countermovement was allowed, but participants had to maintain foot contact with the ground. Each athlete performed three trials, and the greatest distance from the throwing line to the first point of contact was recorded [28,29]. The MBT throw is a reliable, wrestling-specific test for assessing total-body explosive strength, emphasizing the posterior chain, core, and upper body coordination. In wrestling, explosive upper-body power is essential for executing techniques such as throws, lifts, and rapid transitions, as well as for maintaining grip control and initiating directional changes. Given these demands, the MBT test serves as a practical and valid field-based assessment of functional explosive power, making it especially relevant for combat sport athletes.

2.5.3. Vertical jump height test

The Sargent Jump test measured vertical jump height (VJH). The participants chalked the ends of their fingertips. Then, participants stood the shortest distance from a wall, keeping both feet on the ground, reaching up as high as possible with one hand and marking the wall with the tips of their fingers (M1). The participants jumped as high as possible from a static position and marked the wall with chalk on their fingers (M2). VJH was the distance between M1 and M2. The test was repeated three times with a one-minute passive rest between each attempt, and the most significant distance was taken for analysis [30].

2.5.4. Hand grip strength test

The hand grip strength test assessed isometric upper-body strength, which plays a critical role in wrestling for performing holds, clinches, and controlling opponents. Participants sat on a standard chair, and their dominant forearm was placed on the chair’s armrest so that the wrist rested on its edge, with the hand in a neutral position and the thumb facing upward. The dynamometer was held with the thumb on one side and the remaining fingers on the other. To eliminate the influence of gravity, the researcher supported the device during testing. Participants were instructed to squeeze the dynamometer with maximum effort until either exhaustion was reached or no further increase was observed. Each hand was tested three times, and the highest value recorded was used for analysis. This procedure followed standardized protocols to ensure accuracy and reliability [31].

2.5.5. Specific wrestling fitness test

The Specific Wrestling Fitness Test (SWFT) is a validated and sport-specific assessment designed to replicate a competitive wrestling match’s anaerobic and muscular demand (Figure 3). The test comprises three high-intensity 30-second bouts during which the athlete performs repeated suplex throws using a standardized wrestling dummy. Each throwing interval is separated by 20 seconds of passive rest, resulting in a total test duration of approximately two minutes. The athlete is instructed to execute as many technically correct throws as possible during each 30-second active phase. The final score is calculated as the sum of all successful throws across the three work intervals, directly measuring anaerobic power and wrestling-specific endurance. To ensure appropriate load relative to body mass, the test uses three dummy weights: 22 kg for wrestlers weighing ≤74.9 kg, 27 kg for those weighing 75.0–89.9 kg, and 32 kg for those ≥90.0 kg. The SWFT has demonstrated excellent test – retest reliability and internal consistency, with a Cronbach’s alpha of 0.905 and an intraclass correlation coefficient (ICC) of 0.821. Furthermore, physiological markers such as peak blood lactate concentrations exceeding 13 mmol/L and heart rates surpassing 180 bpm confirm the test’s ability to simulate competition-level exertion. As a result, the SWFT serves as a reliable and practical tool for evaluating wrestling-specific fitness and monitoring performance adaptations during training [32,33].

Figure 3.

Structure of the specific wrestling fitness test (SWFT).

2.6. Data analysis

All statistical analyses were conducted using the Statistical Package for the Social Sciences (SPSS, version 26.0; IBM Corp., Armonk, NY, USA). The normality of data distribution was assessed using the Shapiro – Wilk test. A one-way repeated measures ANOVA was employed to examine the main effects of supplementation conditions on physical performance outcomes. A mixed-design repeated measures ANOVA was used to analyze the within-subject factor (pre vs. post) and the between-condition effects for the cognitive outcomes obtained from the Stroop test. Bonferroni-adjusted post hoc comparisons were applied when significant effects were observed to identify pairwise differences using built-in SPSS syntax routines. Effect sizes for both main and interaction effects were reported using partial eta squared (pEta²). Based on Cohen’s guidelines, values of pEta² ≥0.01 were considered small, ≥ 0.059 medium, and ≥ 0.138 large (Cohen, 1988) [34]. Statistical significance was set at p ≤ 0.05. All results are presented as mean ± standard deviation (SD). Graphical representations were generated using GraphPad Prism (version 9.0.0; GraphPad Software Inc., San Diego, CA, USA).

3. Results

The descriptive characteristics of the participants are presented in Table 2. Normality of the data was confirmed using the Shapiro – Wilk test, with all variables demonstrating a normal distribution (p > 0.05).

Table 2.

Means and standard deviation (mean ± SD) of measured variables (n = 12).

Variable		PLA	CAF	THE	CAF+THE
Wall-squat time (s)		100.00 ± 31.29	119.33 ± 33.87	114.41 ± 25.64	148.00 ± 53.48
MBT (m)		11.75 ± 2.05	12.58 ± 2.01	11.82 ± 1.96	13.15 ± 2.40
VJH (cm)		43.41 ± 6.17	47.25 ± 6.13	44.33 ± 7.19	48.41 ± 7.05
Handgrip (kg)		49.41 ± 7.71	53.50 ± 9.43	48.75 ± 9.48	54.41 ± 9.92
SWFT (times)		23.83 ± 3.40	24.75 ± 3.81	23.83 ± 2.88	26.33 ± 3.05
SA (score)		45.25 ± 11.76	58.33 ± 12.61	42.00 ± 11.34	47.75 ± 9.41
TA (score)		45.16 ± 11.45	50.33 ± 12.72	42.08 ± 10.69	47.75 ± 11.24
RT (ms)	Pre	932.25 ± 97.63	896.51 ± 122.74	944.55 ± 137.10	847.45 ± 111.72
	Post	940.12 ± 72.48	840.24 ± 132.63	907.59 ± 141.87	792.92 ± 143.80
CAP (%)	Pre	82.05 ± 15.01	90.39 ± 4.34	91.33 ± 8.34	95.67 ± 5.15
	Post	87.91 ± 8.39	89.21 ± 2.98	81.37 ± 23.85	95.93 ± 5.00

PLA: Placebo, CAF: Caffeine, THE: L-theanine, MBT: Medicine ball throw test, VJH: Vertical Jump Height, SWFT: Specific wrestling fitness test, SA: State anxiety, TA: Trait anxiety, RT: Reaction time, CAP: Correct answer percentage, s: Second, m: Meter, cm: Centimeter, kg: Kilogram, ms: Millisecond, Pre: Before SWFT, Post: After SWFT.

Statistical analysis revealed that the main effect of the intervention on the Wall-squat time was significant (F_1,84 = 9.16, p = 0.002, pEta² = 0.454). Post-hoc Bonferroni tests indicated that participants in the CAF+THE condition exhibited significantly higher performance in the Wall-squat endurance compared to the PLA (p = 0.025), CAF (p = 0.014), and THE (p = 0.048) conditions. However, no significant differences were observed between the CAF and PLA (p = 0.196), THE and PLA (p = 0.744), and CAF and THE (p = 1.000) (Table 3 and Figure 4).

Table 3.

Pairwise comparisons in the four supplementation conditions (n = 12).Variable.

		CAF			THE			CAF+THE
		PLA	THE	CAF+THE	PLA	CAF	CAF+THE	PLA	CAF	THE
Wall-squat time (s)	MD	19.33	4.91	−28.66	14.41	−4.91	−33.58	48.00	28.66	33.58
	sig	0.196	1.000	0.014	0.744	1.000	0.048	0.025	0.014	0.048
MBT (m)	MD	0.82	0.75	−0.56	0.06	−0.75	−1.32	1.39	0.56	1.32
	sig	0.037	0.061	0.152	1.000	0.061	0.007	0.005	0.152	0.007
VJH (cm)	MD	3.83	2.91	−1.16	0.91	−2.91	−4.08	5.00	1.16	4.08
	sig	0.008	0.082	0.789	1.000	0.082	0.012	0.020	0.789	0.012
Handgrip (kg)	MD	4.08	4.75	−0.91	−0.66	−4.75	−5.66	5.00	0.91	5.66
	sig	0.041	0.034	1.000	1.000	0.034	0.001	0.022	1.000	0.001
SWFT (times)	MD	0.91	0.91	−1.58	0.00	−091	−2.50	2.50	1.58	2.50
	sig	0.817	0.717	0.006	1.000	0.717	0.003	0.012	0.006	0.003
SA (score)	MD	13.08	16.33	10.58	−3.25	−16.33	−5.75	2.50	−10.58	5.75
	sig	0.001	0.001	0.001	1.000	0.001	0.284	1.000	0.001	0.284
TA (score)	MD	5.16	8.25	2.58	−3.08	−8.25	−5.66	2.58	−2.58	5.66
	sig	0.031	0.024	0.513	0.102	0.024	0.002	0.039	0.513	0.002
RT-pre (ms)	MD	−35.74	−48.04	49.05	12.29	48.04	97.09	−84.80	−49.05	−97.09
	sig	1.000	0.235	0.484	1.000	0.235	0.060	0.313	0.484	0.060
RT-post (ms)	MD	−99.87	−67.34	47.32	−32.52	67.34	114.66	−147.19	−47.32	−114.66
	sig	0.012	0.209	0.526	1.000	0.209	0.001	0.004	0.526	0.001
CAP-pre (%)	MD	8.34	−0.94	−5.28	9.28	0.94	−4.34	13.62	5.28	4.34
	sig	0.256	1.000	0.001	0.109	1.000	0.473	0.009	0.001	0.473
CAP-post (%)	MD	1.30	7.84	−6.71	−6.54	−7.84	−14.55	8.01	6.71	14.55
	sig	1.000	1.000	0.001	1.000	1.000	0.411	0.021	0.001	0.411

PLA: Placebo, CAF: Caffeine, THE: L-theanine, MBT: Medicine ball throw test, VJH: Vertical Jump Height, SWFT: Specific wrestling fitness test, SA: State anxiety, TA: Trait anxiety, RT: Reaction time, CAP: Correct answer percentage, Pre: Before SWFT, Post: After SWFT, s: Second, m: Meter, cm: Centimeter, kg: Kilogram, ms: Millisecond, MD: Mean Difference.

Figure 4.

Individual responses, means, and standard deviations of the functional tests, SWFT, Stroop test, and state-Trait anxiety test in the different conditions of the study.

PLA: Placebo, CAF: Caffeine, THE: L-theanine, MBT: Medicine ball throw test, VJH: Vertical Jump Height, SWFT: Specific wrestling fitness test, SA: State anxiety, TA: Trait anxiety, RT: Reaction time, CAP: Correct answer percentage, s: Second, m: Meter, cm: Centimeter, kg: Kilogram, ms: Millisecond, Pre: Before SWFT, Post: After SWFT.

* Significant difference compared to the PLA.

# Significant difference compared to the CAF.

¥ Significant difference compared to the THE.

The analysis further demonstrated that the main effect of the intervention on MBT was significant (F₁,₈₀ = 14.39, p = 0.001, pEta² = 0.567). Post-hoc tests revealed substantial increases in MBT in the CAF+THE condition compared to the PLA (p = 0.005) and THE (p = 0.007), and in the CAF compared to the PLA (p = 0.037). Nevertheless, no significant differences were noted between THE and PLA (p = 1.000), CAF and THE (p = 0.061), and CAF+THE and THE (p = 0.152) (Table 3 and Figure 4).

The repeated-measures analysis indicated a significant main effect on VJH (F_2,16 = 10.61, p = 0.001, pEta² = 0.491). Bonferroni tests showed that VJH in the CAF (p = 0.008) and CAF+THE (p = 0.020) conditions were improved compared to the PLA. Additionally, the VJH was higher in the CAF+THE compared to the THE condition (p = 0.012). However, no significant differences were observed in THE (p = 0.197) compared to the PLA (p = 1.000) and CAF (p = 0.082) conditions, and in the CAF+THE compared to the CAF (p = 0.789) (Table 3 and Figure 4).

For the hand grip, the main effect of the intervention was significant (F_2,42 = 10.21, p = 0.001, pEta² = 0.482). Post-hoc Bonferroni tests revealed that the hand grip strength records in the CAF and CAF+THE conditions were higher compared to the PLA (p = 0.041, p = 0.022) and THE (p = 0.034, p = 0.001). No significant differences were observed between the THE and PLA (p = 1.000), and CAF+THE and CAF (p = 1.000) (Table 3 and Figure 4).

Statistical analysis revealed that the main effect of the intervention on the SWFT was significant (F_2,37 = 10.07, p = 0.001, pEta² = 0.478). Post-hoc Bonferroni tests indicated that participants in the CAF+THE condition exhibited higher performance compared to the PLA (p = 0.012), CAF (p = 0.006), and THE (p = 0.003) conditions. However, no significant differences were observed between the CAF and PLA (p = 0.817), THE and PLA (p = 1.000), and CAF and THE (p = 0.717) (Table 3 and Figure 4).

The analysis further demonstrated that the main effect of the intervention on SA in the anxiety test was significant (F_2,13 = 20.10, p = 0.001, pEta² = 0.646). Post-hoc tests revealed increases in SA in the CAF condition compared to the PLA (p = 0.001), THE (p = 0.001), and CAF+THE (p = 0.001). Nevertheless, no significant differences were noted between THE and PLA (p = 1.000), CAF+THE and PLA (p = 1.000), and CAF+THE and THE (p = 0.284) (Table 3 and Figure 4). For the TA, the main effect of the intervention was significant (F_1,34 = 12.16, p = 0.002, pEta² = 0.525). Post-hoc Bonferroni tests revealed that the TA results in the CAF and CAF+THE conditions were higher compared to the PLA (p = 0.031, p = 0.039) and THE (p = 0.024, p = 0.002). No significant differences were observed between the THE and PLA (p = 0.102), and CAF+THE and CAF (p = 0.513) (Table 3 and Figure 4).

The mixed repeated measure analysis indicated that the main effect of the intervention (F_1,81 = 11.69, p = 0.001, pEta² = 0.515) was significant on the RT in the Stroop test. Also, the Bonferroni tests revealed that the RT post-SWFT was less in the CAF+THE compared to the PLA (p = 0.004) and THE (p = 0.001), and in the CAF compared to the PLA (p = 0.012). However, no significant differences were observed in THE compared to the PLA (p = 1.000) and CAF (p = 0.209), and in the CAF+THE compared to the CAF (p = 0.526) in the RT post-SWFT (Table 3). There were no considerable differences between the study conditions in the RT pre-SWFT (p > 0.05). Additionally, the results of the post-hoc test indicated that there is no significant difference in the RT between pre-SWFT and post-SWFT in the different conditions of the study (p > 0.05) (Figure 4). For the CAP, the mixed repeated measure analysis showed that the main effect of the intervention was significant (F_1,26 = 6.25, p = 0.020, pEta² = 0.363). In addition, the Bonferroni post-hoc test showed that the CAP pre-SWFT was higher in the CAF+THE compared to the PLA (p = 0.009) and CAF (p = 0.001). Nevertheless, no significant difference was observed between CAF+THE and THE (p = 0.473), THE and PLA (p = 0.109), THE and CAF (p = 1.000), and CAF and PLA (p = 0.256). Additionally, the CAP post-SWFT was higher in the CAF+THE compared to the PLA (p = 0.021) and CAF (p = 0.001). However, no significant difference was observed between CAF+THE and THE (p = 0.411), THE and PLA (p = 1.000), THE and CAF (p = 1.000), and CAF and PLA (p = 1.000) (Table 3). Moreover, the results of the post-hoc test indicated that there is no significant difference in the CAP between pre-SWFT and post-SWFT in the different conditions of the study (p > 0.05) (Figure 4).

4. Discussion

4.1. Overview of findings

This study investigated the ergogenic effects of CAF and THE, alone and in combination, on elite wrestlers’ performance. The results strongly support a synergistic benefit of combining CAF+THE. Specifically, the CAF+THE condition outperformed placebo and the single supplements on multiple physical performance measures (e.g. greater isometric strength, explosive power, and sport-specific endurance) and cognitive performance under fatigue (faster reaction times and higher accuracy). Notably, CAF+THE also had the lowest anxiety and fewest side effects, whereas caffeine alone (3 mg/kg) elevated anxiety and induced tachycardia, possibly negating some benefits. These findings highlight that co-ingesting L-theanine allows athletes to harness caffeine’s well-known performance benefits while stabilizing mood and arousal. Such dual advantages are highly relevant for combat sport athletes like wrestlers, who require peak physical output and sharp mental focus under high stress.

4.2. Ergogenic mechanisms of caffeine and L-Theanine

The performance enhancements observed can be understood through the complementary mechanisms of Caffeine and L-theanine. Caffeine is a potent adenosine receptor antagonist in the central nervous system (CNS), which leads to increased neural activation, elevated catecholamine (e.g. adrenaline) levels, and enhanced motor unit recruitment [4]. These effects increase alertness, reduce perceived exertion, and improve neuromuscular function. For example, caffeine’s CNS stimulation and its action on skeletal muscle calcium handling augment muscle fiber contractility and power output [35]. Caffeine has been shown to enhance calcium release from the sarcoplasmic reticulum, accelerating cross-bridge cycling in muscle fibers [36]. This physiological effect can explain explosive movement and strength improvements, facilitating greater force production. Additionally, caffeine can increase dopamine and acetylcholine levels, improving focus and decision-making speed [37].

L-Theanine, an amino acid in tea, has almost the opposite modulatory effect: it promotes a calm but alert mental state. L-theanine readily crosses the blood – brain barrier and influences neurotransmitters by increasing GABAergic and dopaminergic activity while reducing excitatory signaling. It stimulates alpha brain-wave activity associated with relaxed concentration [12,38]. These neurochemical actions produce anxiolytic and anti-stress effects – essentially “taking the edge off” caffeine’s stimulation. In practical terms, L-theanine can mitigate caffeine’s side effects (anxiety, jitters, elevated blood pressure) by counteracting excessive CNS excitation [9]. Prior studies confirm that adding theanine to caffeine blunts caffeine’s vasoconstrictive effect on cerebral blood flow and prevents the rise in stress hormones, without causing sedation [16]. In the present context, this means athletes can achieve an optimal arousal level: caffeine provides the energy and neural drive, while theanine prevents overstimulation and helps maintain focus. The net result is enhanced physical and cognitive performance, as observed with the CAF+THE combination.

4.3. Improvements in physical performance

Muscular Strength and Power: The combination of CAF and THE led to notable gains in strength and explosive power measures. Handgrip strength, an indicator of isometric upper-body force, improved by ~ 10–12% with CAF+THE relative to placebo, a benefit consistent with caffeine’s known impact on grip strength. Caffeine alone also increased grip strength, supported by prior meta-analyses showing caffeine’s efficacy for maximal voluntary contraction strength [39]. Mechanistically, caffeine likely improved grip strength via enhanced motor unit recruitment and firing rates and reduced perceived exertion during the squeeze [4,39]. These neuromuscular effects allow athletes to exert greater force. The addition of THE did not significantly further increase maximal grip force beyond CAF in our study, which aligns with the idea that caffeine was the primary driver of acute strength gains. However, THE’s calming effect may have indirectly helped athletes approach their max effort by reducing performance anxiety [10,40]. Thus, while caffeine is ergogenic for strength, the combination ensures the athlete can fully tap into that strength potential under competitive stress.

Caffeine-containing conditions showed clear benefits for explosive power, measured by the medicine ball throw (upper-body power) and vertical jump (lower-body power). CAF+THE improved medicine ball throw distance by ~ 12% vs placebo, and vertical jump height by ~ 11% vs placebo – both significant gains. Caffeine’s role in explosive movements is well documented: by antagonizing adenosine in muscle and nerve tissue, caffeine increases motor neuron firing and enhances muscle fiber contractility [41,42]. It also improves sodium-potassium pump efficiency and calcium availability in muscle, contributing to greater power output [4,43]. Our findings concur with other research in athletes; for instance, a 3 mg/kg caffeine dose has been shown to increase vertical jump height in elite sportsmen acutely [44]. Similarly, Saremi et al. (2025) demonstrated that a 3 mg/kg dose significantly boosted peak anaerobic power in professional kickboxers [7]. While these results support the utility of moderate caffeine dosing, it is also important to note that studies using multiple dosing levels – such as Durkalec-Michalski et al. (2019) – have shown that higher intakes (e.g. 6–9 mg/kg) can elicit greater performance improvements in combat sports, particularly for anaerobic power and repeated-effort tasks [8]. Thus, while 3 mg/kg appears sufficient to produce measurable benefits, it may not fully optimize performance for all athletes or contexts. In our study, adding L-theanine did not create additional power beyond caffeine alone, as evidenced by the lack of a significant difference in jump or throw performance between CAF+THE and CAF (no significant CAF+THE vs CAF difference in jump or throw performance). This indicates that caffeine was the primary ergogenic factor. Crucially, L-theanine did not attenuate these power benefits, aligning with findings in other athlete populations showing that caffeine + theanine can enhance cognitive outcomes without impairing physical performance [15]. Overall, our data support the effectiveness of moderate caffeine dosing for enhancing explosive power in combat sports, while also acknowledging that higher doses may provide a further advantage, depending on individual tolerance and performance goals.

Muscular Endurance and Sport-Specific Performance: One of the most striking outcomes of this study was the enhancement of fatigue resistance and sport-specific work capacity observed with the combined CAF+THE supplementation. In the wall-squat test – a standard measure of lower-body isometric muscular endurance – athletes in the CAF+THE condition maintained the squat position 24% longer than when supplemented with CAF alone and 48% longer than placebo. This considerable improvement highlights a synergistic interaction between caffeine and L-theanine that appears to extend beyond caffeine’s known, yet often inconsistent, effects on muscular endurance. Although caffeine is well-documented to delay fatigue and reduce perceived exertion [4], not all studies consistently demonstrate enhanced endurance capacity following caffeine ingestion, particularly at moderate doses. Adding L-theanine may offer a critical augmentation by mitigating the perception of discomfort and mental fatigue during sustained muscular effort. Neurophysiologically, L-theanine’s ability to increase alpha-wave brain activity and promote a relaxed but focused state could have allowed athletes to tolerate the accumulating pain better and maintain posture for a more extended period [12]. Meanwhile, caffeine likely contributed by elevating catecholamine levels and enhancing lipolysis, thereby sparing muscle glycogen, a known mechanism that supports sustained isometric efforts [45]. Thus, the co-administration of caffeine and L-theanine seems to produce a complementary effect: enhancing both the physiological and psychological aspects of endurance performance.

This synergy was even more evident in the SWFT, a circuit of throws that simulates the repeated explosive efforts of a wrestling match. Wrestlers could perform more throws in the CAF+THE trial than in CAF alone, THE alone, or placebo. Notably, CAF alone at 3 mg/kg did not significantly outperform placebo on the SWFT in our study. This is an intriguing result, given caffeine’s established ergogenic reputation. One likely factor is the adverse side effects experienced with caffeine. Approximately 92% of participants reported tachycardia (elevated heart rate) after caffeine, and anxiety was significantly higher with CAF alone. These symptoms can impair coordination, focus, and the willingness to push to exhaustion, thereby blunting caffeine’s performance benefits in complex tasks like the SWFT. In contrast, when THE was co-ingested with CAF, reports of anxiety dropped to only 8% (vs. 91% with caffeine alone), and tachycardia was far less frequent. The calmer physiological state likely allowed athletes in the CAF+THE condition to fully exploit caffeine’s physical ergogenic effects, resulting in superior throwing performance. This finding aligns with previous research in combat sports: studies in judo and jiu-jitsu have shown caffeine can improve the number of throws or high-intensity efforts in sport-specific tests Merino-Fernandez et al. (2022) [46], Carmo et al. (2021) [47], and Astley et al. (2021) [48], but those studies typically used higher caffeine doses (6–9 mg/kg). Our data suggest that at a lower dose, caffeine’s benefit might only manifest if the athlete’s state anxiety is controlled. Thus, L-theanine’s role in enabling caffeine’s effect is especially critical for endurance-type tasks under stress. Coaches and athletes in combat sports could leverage this by using a moderate caffeine dose with theanine to achieve performance gains comparable to high-dose caffeine, but with fewer side effects.

4.4. Cognitive performance and mental focus

In high-intensity sports like wrestling, cognitive function (such as reaction speed, decision-making, and accuracy under pressure) can be as important as physical prowess. A key finding of this study is that the CAF+THE combination enhanced cognitive performance to a greater extent than either supplement alone. On the Stroop reaction test, which was administered before and after a fatiguing exercise, CAF+THE consistently led to faster reaction times and better accuracy. Pre-SWFT, all supplemented conditions showed some improvement in RT compared to placebo, but only CAF+THE maintained a significant advantage under post-SWFT conditions. Caffeine alone failed to speed up reactions once the athletes were exhausted, likely due to fatigue overwhelming its stimulant effect. L-theanine alone did improve RT modestly (notably in our study, L-theanine improved post-SWFT RT vs. placebo by ~ 2%), which aligns with its known ability to enhance attentional focus in some contexts [9,12]. However, the largest and most significant RT gains resulted from the combination: CAF+THE, which not only had the fastest RTs before and post-SWFT but also surpassed caffeine alone by a considerable margin post-SWFT. This indicates a synergistic interaction whereby theanine helps sustain and extend caffeine’s cognitive benefits when the athlete is tired [15].

Accuracy in the Stroop test (percent of correct responses) displayed a similar pattern. All groups slightly improved accuracy pre-SWFT, but post-SWFT, both CAF and THE alone lost their efficacy – accuracy dropped back toward placebo levels. In contrast, the CAF+THE condition maintained a high level of accuracy even in the fatigued state, significantly above placebo and the single supplement conditions. This suggests the combination speeds up cognitive processing without a trade-off in accuracy, even under physical stress. The complementary neurochemical effects provide a plausible explanation: caffeine increases vigilance and accelerates decision-making through heightened dopaminergic and cholinergic signaling, while L-theanine may prevent errors by decreasing mental distractions (mind-wandering) and enhancing focused attention [17]. Evidence from Electroencephalography (EEG) and event-related potential (ERP) studies supports this idea – for example, Kahathuduwa et al. reported that CAF+THE led to more efficient neural resource allocation to target stimuli, correlating with improved reaction time and accuracy [49]. Likewise, a recent randomized controlled crossover study by Yilmaz et al. (2023) found that combining caffeine with L-theanine significantly improved cognitive performance and motor accuracy in elite curling athletes. Compared to caffeine or theanine alone, the CAF+THE group exhibited the fastest Stroop reaction times and lowest error rates, as well as superior performance across all shot types [15]. Our findings mirror these results in a wrestling context, underscoring that the CAF+THE pairing is particularly effective for preserving high-level cognitive function when an athlete is exhausted. In practical terms, a wrestler on this combination might make smarter tactical decisions and react more swiftly to an opponent’s moves in the late stages of a match, which could be decisive for victory.

Not all studies have found facilitative cognitive effects of the CAF-THE combo; some early research using lower doses indicated L-theanine might even antagonize caffeine’s alertness in certain simple tasks [9,14]. For instance, Rogers et al. reported that THE (~200 mg) co-administered with caffeine slowed simple reaction time, possibly by counteracting arousal too strongly [14]. However, task complexity and dosage are critical factors [9]. Rogers’ finding likely reflects a very calm scenario (tea consumption in rested subjects), whereas in high-stress, fatigued athletes, we see L-theanine helping more than hindering. Indeed, multiple studies now confirm that in cognitively demanding or fatigue-inducing settings, the combination is superior: our results and those of others suggest that theanine’s calming effect does not impair – and supports – performance when individuals are under pressure or tired [9,15,17]. This context-dependent synergy is essential for sport applications. In summary, CAF+THE can be considered an effective “nootropic” blend for athletes, accelerating reaction speed and maintaining accuracy when it counts most.

4.5. Mitigating side effects: anxiety and tachycardia

A key advantage of co-administering THE with CAF was its ability to markedly reduce the adverse side effects commonly associated with CAF consumption, particularly anxiety and tachycardia. In our study, CAF alone (3 mg/kg) significantly increased state anxiety and led to tachycardia in 92% of participants, consistent with prior research highlighting caffeine’s stimulatory effect on the sympathetic nervous system, especially in low habitual users [4,14]. Such symptoms are detrimental in combat sports, where excessive arousal may impair decision-making, coordination, and fine motor control under stress. However, when THE was combined with CAF, the incidence of anxiety symptoms dropped dramatically to just 8%, even lower than placebo, and the frequency of tachycardia was also substantially reduced. This supports L-theanine’s role as an anxiolytic agent. Mechanistically, L-theanine increases central GABA and serotonin levels while lowering excitatory neural signaling, thus dampening the stress-related autonomic response induced by caffeine. Additionally, it may promote parasympathetic activation and nitric oxide – mediated vasodilation, mitigating caffeine-induced vasoconstriction [9,10].

These results align with previous studies showing that the combination of caffeine and L-theanine improves mood and cognitive performance while reducing anxiety and overstimulation [9,17,50]. Importantly, our results suggest that L-theanine’s calming effect enabled athletes to harness caffeine’s ergogenic potential without overstimulation. This is especially relevant in high-anxiety sports like wrestling, where composure under pressure is critical. The superior SWFT performance observed in the CAF+THE group may be partly attributable to this improved psychophysiological state. Furthermore, individual variation in caffeine sensitivity – potentially driven by ADORA2A gene polymorphisms – may explain the heightened anxiety observed in some athletes following caffeine alone [51]. While we did not genotype participants, the uniform mitigation of side effects in the CAF+THE condition indicates that THE may buffer these genetic sensitivities to a large extent. Overall, combining THE with CAF appears to be a practical and evidence-based strategy to enhance performance while minimizing undesirable stimulant-related symptoms in combat athletes.

4.6. Implications for wrestling and combat sports

The performance and cognitive benefits observed from CAF+THE supplementation in this study are strongly relevant to wrestling and other combat sports. Wrestling requires a unique integration of strength, power, anaerobic endurance, and rapid tactical decision-making, all performed under physical fatigue and psychological stress conditions [1–3]. Our findings suggest that a moderate dose of CAF (3 mg/kg) combined with an equal dose of THE offers a practical ergogenic strategy to support these demands. Wrestlers using this combination experienced improvements in key performance metrics – grip strength for clinch control, lower-body explosiveness for takedowns, and muscular endurance for sustained effort across rounds [1–3]. They also demonstrated superior cognitive function and reduced anxiety, supporting better concentration and reaction time under fatigue, which is crucial for defensive counters and technical execution [15]. This dual-action profile is particularly beneficial in sports like wrestling, where a split-second delay or mental lapse can result in scoring or conceding critical points. These findings are consistent with prior research showing caffeine’s efficacy in combat sports such as judo, Brazilian jiu-jitsu, and kickboxing [7,46–48,52], where caffeine supplementation improved sport-specific test performance and sparring output. However, those studies typically used higher caffeine doses (e.g. 5–6 mg/kg), which may not be well-tolerated by all athletes. Our results extend the literature by demonstrating that a lower CAF dose (3 mg/kg), when paired with THE, may deliver comparable or superior performance benefits with fewer side effects. This has practical relevance for weight-class athletes who are sensitive to diuresis, sleep disruption, or anxiety associated with higher caffeine intake. Our findings indicate that adding THE may enhance the consistency and safety of this response, especially for caffeine-naïve or anxiety-prone athletes. L-theanine’s anxiolytic effects help attenuate the overstimulation commonly reported with caffeine, making it an ideal adjunct for combat sport athletes seeking focus and emotional regulation during competition. This aligns with previous findings by Haskell et al. (2008) and Kahathuduwa et al. (2018), showing that the combination enhances cognitive control while reducing stress-induced impairments [17,50].

Athletes and coaches should, however, consider individual variability in caffeine tolerance and habituation. While low-caffeine users may experience more potent effects at lower doses, including anxiety, habitual users may require slightly higher amounts to achieve ergogenic benefits [4]. L-theanine may help blunt overstimulation in both cases, enabling broader applicability of moderate caffeine strategies across athlete populations. Both caffeine and theanine are legal, widely available, and permitted by WADA, though testing protocols during training are recommended to assess individual response and tolerance before competition use.

4.7. Limitations and future research directions

This study has several methodological limitations that should be acknowledged. First, the study lacked a no-treatment control condition, so we could not independently monitor the placebo effect or distinguish improvements due to test familiarity. This was due to limited access to elite wrestlers, as their coaches restricted the number of testing sessions. Second, we did not collect physiological data such as serum caffeine or theanine concentrations, catecholamine levels, or heart rate variability. This could have provided more profound insight into the pharmacokinetics and neuroendocrine responses to supplementation. Third, genetic variability, particularly related to caffeine metabolism (CYP1A2) and sensitivity (ADORA2A), was not assessed; such polymorphisms may partly explain interindividual differences in anxiety response and ergogenic benefit. Fourth, our sample size was relatively small (n = 12), homogenous (male, similar training background), and underpowered to explore subgroup interactions (e.g. habituated vs. non-habituated caffeine users). As such, the results may not be generalizable to female athletes, mixed-gender teams, or athletes with higher habitual caffeine intake. Finally, self-reported anxiety and perceptual responses measures were used rather than standardized psychophysiological tools (e.g. EEG, cortisol), which may limit the objectivity of those findings.

Future studies should include a no-treatment control condition to better isolate placebo and learning effects. Monitoring physiological markers (e.g. blood caffeine/theanine levels, cortisol) would clarify absorption and mechanistic pathways. Genetic profiling (e.g. CYP1A2, ADORA2A) could help identify individual responses. Expanding to larger and more diverse samples, particularly female athletes, would enhance generalizability. Research should also test varying CAF: THE dose ratios and assess long-term use across training cycles. Finally, field studies in real wrestling competition settings must validate these effects under actual performance conditions.

5. Conclusion

This study provides novel evidence that co-supplementation with moderate doses of caffeine (3 mg/kg) and L-theanine (3 mg/kg) enhances both physical and cognitive performance in elite wrestlers more effectively than either supplement alone. The combination improved isometric strength, explosive power, muscular endurance, and sport-specific performance while sharpening attention and reaction time, especially under fatigue. Notably, L-theanine mitigated the anxiety and tachycardia induced by caffeine alone, resulting in a more stable psychophysiological response. From a practical standpoint, this combination offers a safe, WADA-compliant strategy for combat athletes seeking dual-domain enhancement. Coaches and athletes are advised to trial CAF+THE protocols during training to fine-tune timing, dose, and individual response. A 60-minute pre-competition intake of 3 mg/kg of each compound appears effective. This approach may be especially beneficial for athletes prone to pre-competition anxiety or in multi-bout tournaments where sustained focus and energy are crucial.

Funding Statement

This research received no external funding. Institutional Review Board Statement: The study was conducted in accordance with the Declaration of Helsinki and approved by the Research Ethics Committees of the Faculty of Psychology and Educational Sciences, Shiraz University (Approval Code: IR.US.PSYEDU.REC.1403.053, 10 July 2024).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors on request due to (specify the reason for the restriction, e.g. privacy, legal or ethical reasons). The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Informed consent statement

Informed consent was obtained from all subjects involved in the study.