Players were recruited from academic handball teams according to the criteria for inclusion and exclusion. Inclusion criteria were as follow: men, age 18-45, good general health determined based on a medical examination including the assessment of resting ECG and resting blood pressure. Exclusion criteria were hypersensitivity to any of the product components (verified based on a declaration in a personal questionnaire) and no injury in the six months preceding the study. Players were asked to refrain from consuming caffeine, strong tea, any additional supplements or ergogenic aids, alcohol-containing products for the two weeks preceding the survey, and not doing strenuous training for 24 hours before the examination. The participants were asked not to consume anything for 3 hours before the test.
All participants attended a familiarization session one week before the study. In the main part of the study the players were tested under three conditions: placebo, caffeine, and MS supplementation in random order. Participants repeated the testing session every three days. After consuming either a placebo or the supplement solution (CAF or MS), handball players rested for 15 minutes. Standard warm-up started with 10 min run at 60%–75% of maximal heart rate. After the run participants performed various dynamic stretching exercises for five minutes. First, the agility test was performed, followed by a countermovement jump.
Players were acquainted with the purpose and course of research. They also provided their written consent to participate in the project. In the case of soccer players. The study was approved by the Ethical Committee of the University of Physical Education in Katowice (Poland; opinion No. 2/2018) and conformed to the ethical requirements of the 1975 Helsinki Declaration.
Twenty–four recreationally-trained handball male players (body mass = 74.6±8.8 kg; body height = 179±7.2 cm; age = 23.8±1.4 years) were involved in this study. Participants trained up to three pieces of training per week with medium to high-intensity (including resistance training) and played one match (academic league) in a week.
Forty-five minutes before testing, players were randomly provided with either a) placebo (PL): 250 ml of the flavored water; or b) caffeine, flavored water containing: anhydrous caffeine (200 mg) (Biesterfeld International, Poland) and guarana extract (200 mg) (EVER Pharma, Lyon, France): 300 mg of caffeine in total, mixed with water (250 ml), or c) 9.6 g MS powder, (Olimp, Poland), mixed with 250 ml of water. MS contained: L-citrulline (3 g), beta-alanine (2 g), taurine (750 mg), L-arginine (500 mg), L - tyrosine, anhydrous caffeine (200 mg), guarana extract (200 mg; in total 300 mg of caffeine), barley extract (150 mg), cayenne pepper seed extract (25 mg), black pepper extract (7.5 mg) and Huperzia serrata extract (3 mg). The guarana extract was standardized for 50% caffeine content. The amount and chemical form of caffeine consumed by players were the same in the caffeine and MS conditions, and its dosage was about 5 mg/kg.
Reactive agility test: 1-1-2 (Y-test)
Four pairs of electronic timing gates system (Fusion Smart Speed PRO, Brisbane, Australia) have been set, as pointed out in Figure 1. Participants began each trial 20 cm in front of the starting line. After the first 5 meters run at maximum speed in a straight line toward the second timing gate, the system indicated the further direction of the subject's movement. After crossing the middle gate, the next gate lights turned on, forcing the participant to change direction as quickly as possible while maintaining the maximum possible speed run for the last 10 m. Participants had completed the test until two sprints to either side were recorded. The best trial for each side was used for analysis. The test 1-1-2 scheme is shown in Figure 1.
The Optojump system (Optojump, Microgate, Bolzano, Italy) consisting of two bars (transmitting and receiving, 1 m apart) was used to evaluate the jump height in the countermovement jump. CMJ was performed without arm swing (i.e., hands placed on hips). Participants were instructed to start from an erect position and make a downward movement before taking off from the floor. During the CMJ, there was no interval for rest between the 2 phases of the jump (eccentric and concentric phases. All players performed two trials with a 60 s interval between each attempt. The better result of these two trials was taken for further analysis as previously described [18, 19, 20].
The data are presented as means and standard deviations (mean ± SD). The significance of differences between conditions was done using analysis of variance (ANOVA). Post hoc analysis was carried out using Tukey’s test. Data distribution was checked using the Shapiro–Wilk test. Homogeneity of variance within the groups was tested via Levene’s test (variance of the analyzed parameters was similar in both groups). The effect size (partial eta squared (η2) was calculated and interpreted as small (0.01), medium (0.06), or large (0.14) . Statistically significant results were defined as a p-value of <0.05. The following software was used to perform the calculations: STATISTICA 13.1 (StatSoft, Tulsa, OK, USA).