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The change of direction (COD) ability is perhaps the most significant fitness component in team sport games. One of the best ways to develop COD as well as other components of the game in soccer is the regular inclusion of small sided games (SSGs) in the training process. Therefore, the aim of this research was to determine changes in physiological and kinematic variables in repeated SSGs in youth soccer players. Additionally, we investigated the relationship between selected IMA variables such as acceleration, deceleration and changes of direction. Participants included sixteen U17 soccer players from a 2nd league professional team with a high aerobic capacity. The study design involved six 3-min 4 × 4 SSGs with goalkeepers and with a 3-min rest interval between games, during two training sessions played on a field of 25 x 35 m. The results showed that the intervention protocol consisting of repeated SSGs generated an intensity below the anaerobic threshold. This allowed for the maintenance of all variables (Heart Rate, Total Distance Covered, Velocity, Acceleration, Deceleration, Change of Direction) at a similar level throughout the subsequent six SSGs. The analysis revealed that in the six SSGs, players performed the most Acc and Dec, then COD Right and the least COD Left. From the third game on, a decrease in the number of COD Right was noticed. We hypothesized that progressive neuromuscular fatigue on the dominant side caused a more symmetrical trend in COD.

Cardiovascular safety of marathon running middle-aged amateurs remains unclear. We previously hypothesized that transient release of cardiac troponin I (cTnI) and N-terminal pro-B-type natriuretic peptide (NT-proBNP), in addition to an acute inflammatory response to exercise, may be the cause.To evaluate the effects of running a marathon on inflammatory biomarkers, and its impact on cardiovascular function.Thirty-three healthy male amateur runners aged ≥50 (mean age: 57 ±7 years) were enrolled in the study. Venous blood samples were obtained before the marathon, just after the race, and 2-4 days and 7 days after the marathon. Using novel single molecule counting (SMC) technology, we measured plasma concentrations of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α). White blood cell (WBC) count was measured using a certified hematology analyzer. The results were related to previous analyses on cardiovascular stress and endothelial function biomarkers. Transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) were used to determine myocardial function.We observed a sharp rise of all studied biomarkers after the race, which subsequently normalized after 2-4 days and stayed within the normal range 7 days after the race. We found no correlation between inflammatory and cardiovascular stress biomarkers. Transthoracic echocardiography and CMR did not show ischemic or inflammatory myocardial damage.Marathon running is associated with a sharp and significant rise in inflammatory and cardiovascular stress biomarkers. We found no connection between immune activation and cardiac biomarker release. Cardiovascular imaging showed no myocardial damage due to ischemia or inflammation.

The aims of this study were (1) to determine the match running performance required by different teams based on their final ranking position and (2) to analyze the association between match running performance variables and team success at the end of the season. A total of 1,224 match observations from professional soccer teams competing during two consecutive seasons in the German Bundesliga were analyzed. In addition, the final league ranking position and the total of points obtained by each team at the end of the season were registered for the analysis of the association between team success and match running performance. The main findings were that high ranked teams covered the greatest total distance with ball possession, sprinting distance with ball possession, and completed the greatest number of sprinting actions with ball possession and maximal velocity. Moreover, total distance covered with possession of the ball and maximal velocity were the most important variables to predict the total of points obtained at the end of the season. Specifically, the relative contribution of total distance covered with ball possession to the total of points obtained was greater than maximal velocity. Training programs for professional soccer players should be focused on improving the sprint capacity and running with possession of the ball (e.g., transitional tasks and small-sided games). Moreover, this has implications for injury prevention, physical, psychological, and technical-tactical training since today’s soccer requires players to engage in repeated high-intensity actions, reach maximum speeds above 9 m/s, and develop technical-tactical coordination when running with the ball.

BACKGROUND: This investigation aimed to analyze differences in running performances amongst playing positions between the first and second halves of soccer matches and at 5-minute intervals during matches. METHODS: Data were collected from 179 soccer players during 20 UEFA Champions League (UCL) 2020/2021 group stage matches. Data were examined using the InStat Fitness semi-automatic video system. Eight variables were selected to quantify players’ running performance (RP). Players were categorized based on positional groups: central defenders (CD), fullbacks (FB), central midfielders (CM), wide midfielders (WM), and forwards (FW). Univariate differences in RP were analyzed using ANOVA and the t-test for dependent samples and multivariate differences were identified using canonical discriminant analysis. RESULTS: The main findings were that all positions achieved significantly higher average speeds and walking distances in the first half of the match than in the second half. Furthermore, analysis of positions showed that CM covered more distance than CD in all 5-minute intervals. In addition, WM performed more high-intensity running than CD in all 5-minute intervals and FW performed more high- intensity running than all other playing positions. CONCLUSIONS: The findings from the present study should help coaches design training exercises that are specific to parts of a match. Moreover, the findings can help provide better understanding of match demands and individualization of training. Analysis of 5-minute intervals may also help coaches understand the stages of a match where player substitutions will be most effective.

IntroductionThe research examines the relationship between marathon performance and muscle stiffness changes from pre to marathon in recreational runners aged 50+ years.MethodsThirty-one male long-distance runners aged 50–73 years participated in the experiment. The muscle stiffness of quadriceps and calves was measured in two independent sessions: the day before the marathon and 30 min after the completed marathon run using a Myoton device.Results and DiscussionThe 42.195-km run was completed in 4.30,05 h ± 35.12 min, which indicates an intensity of 79.3% ± 7.1% of HRmax. The long-term, low-intensity running exercise (marathon) in older recreational runners and the low level of HRmax and VO2max showed no statistically significant changes in muscle stiffness (quadriceps and calves). There was reduced muscle stiffness (p = 0.016), but only in the triceps of the calf in the dominant (left) leg. Moreover, to optimally evaluate the marathon and adequately prepare for the performance training program, we need to consider the direct and indirect analyses of the running economy, running technique, and HRmax and VO2max variables. These variables significantly affect marathon exercise.

This study aimed to compare the effects of 1×1 small-sided games (SSGs) with different bout durations on external (ETL) and internal training loads (ITL) in youth soccer players. Twenty U18 players were divided into two groups performing six 1×1 SSGs with 30 and 45 s bout durations. ITL indices, including the percentage of maximum heart rate (HR), blood lactate (BLa) level, pH, bicarbonate (HCO3¯) level, and base excess (BE) level, were measured at rest, after each SSG bout, and 15 and 30 min after the entire exercise protocol. ETL (Global Positioning System metrics) was recorded during all six SSG bouts. The analysis showed that the 45 s SSGs had a greater volume but a lower training intensity than the 30 s SSGs. A significant time effect was observed in all ITL indices and a significant group effect in the HCO3¯ level only. Finally, the changes in the HR and HCO3¯ level were smaller in the 45 s SSGs than in the 30 s SSGs. In conclusion, the HR and BLa level during short-bout SSG training have limited diagnostic value for ITL. Extending ITL monitoring using other indicators, such as the HCO3¯ and BE levels, appears reasonable.

The aim of the study was to determine the effects of a 6-month training cycle on muscle damage and inflammatory markers in youth male soccer players. Twenty-one soccer players were tested four times: at the beginning (T1) and immediately after the pre-season period (T2), in the middle (T3) and at the end of the competitive period (T4). Muscle damage and inflammatory markers were determined in blood taken 36 hours after the match. Throughout the training cycle significant increases (p < 0.05) of creatine kinase (T1: 254.4 U·L-1; T4: 304.2 U·L-1) and lactate dehydrogenase (T1: 382.8 U·L-1; T4: 453.2 U·L-1) activities were observed. Significant changes (p < 0.05) in platelet count (T1: 210.5·109·L-1; T4: 234.2·109·L-1), percentage of lymphocyte (T1: 39.80%; T4: 42.97%), monocyte (T1: 6.88%; T4: 9.99%) and granulocyte (T1: 53.32%; T4: 47.05%) as well as in granulocyte-to-lymphocyte (T1: 1.41; T4: 1.17) and lymphocyte-to-monocyte (T1: 6.21; T4: 4.46) ratios were noted. The correlation analysis revealed statistically significant relationships (p < 0.05) between: myoglobin and the percentage of leukocyte subpopulations and the granulocyte to lymphocyte ratio; lactate dehydrogenase and the percentage of monocyte; lactate and leukocyte count. In conclusion, the reported muscle damage and inflammatory markers in T3 and T4 indicate the need for fatigue status monitoring in youth soccer players, especially in the competitive period. Moreover granulocyte to lymphocyte and lymphocyte to monocyte ratios proved to be sensitive to fatigue changes and therefore can provide coaches and sport scientists with a broader perspective on the biochemical monitoring of training status in soccer players.

This study aimed to assess the capacity for repeated maximal effort (RME) of soccer players in the thermo-natural conditions (NC) and in simulated conditions for the 2022 FIFA World Cup in Qatar (QSC). Twenty-four semi-professional soccer players participated in the study. The exercise test consisted of ten 6-second maximal efforts on a cycloergometer. A 90-second passive rest interval was used. The test was performed in a Weiss Technik WK-26 climate test chamber in two different conditions: 1) thermo-neutral conditions (NC—20.5°C; 58.7% humidity); and 2) simulated conditions for the 2022 World Cup in Qatar (QSC—28.5 ± 1.92°C; 58.7 ± 8.64% humidity). Power-related, physiological, psychomotor, blood, and electrolyte variables were recorded. Results showed that (1) players achieved higher peak power (max 1607,46 ± 192,70 [W] - 3rd rep), needed less time to peak power (min 0,95 ± 0,27 [s] - 3rd rep), and had a higher fatigue slope (max 218,67 ± 59,64 [W/sek] - 7th rep) in QSC than in NC (in each repetition of study protocol); (2) between the 1st repetition and subsequent repetitions a number of significants in among physiological, blood-related, and electrolyte variables were noted, but their direction was similar in both simulated conditions (e.g. V’O2/kg 37,59 ± 3,96 vs 37,95 ± 3,17 [ml/min/kg] - 3rd rep, LAC 13,16 ± 2,61 vs 14,18 ± 3,13 [mg/dl] - 10th rep or K 4,54 ± 0,29 vs 4,79 ± 0,36 [mmol/l] - 2nd rep when compare QCS and NC respectively); (3) an 8°C of temperature difference between the climatic conditions did not significantly affect the soccer players’ physical and physiological responses in RME. The study results can be used in the design of training programs aimed to increase players’ physiological adaptations by simulating soccer-specific conditions of play in terms of anaerobic capacity, in particular, repetitive maximal efforts. These findings will be useful during the upcoming 2022 World Cup in Qatar and in locations where high ambient temperatures are customary.

The study detailed here has sought to assess the physical and technical activity engaged in by football players in the light of the direction of travel in which time zones were crossed as players transferred from training centres to match venues, in the context of matches played at the 2018 FIFA World Cup in Russia. The material consisted of 945 observations of 340 players. Analysed: total distances covered [km], distances covered with high-intensity running (20-25 km/h) [m], numbers of sprints, numbers of shots, numbers of passes, pass accuracy [%] and the official ranking of national teams. Three categories of time-zone shift (training centre → match venue) were taken account of, i.e. (1) West→East (WE), (2) Same Zone (SZ) and (3) East→West (EW). Analysis of results revealed that players in the EW and SZ categories were able to achieve results significantly better than those moving WE (total distances covered H = 11.815(2); p = 0.003; numbers of passes H = 7.630(2); p = 0.022), and this in relation to team placings in the end-of-tournament ranking (H = 18.099(2); p = 0.001). The results will be valuable in searching places for training centres during future FIFA World Cup and UEFA European Championship competitions.

The present study attempts to assess changes in soccer players’ physical and technical activity profiles due to thermal stress, measured with the Universal Thermal Climate Index (UTCI), in training centres and during matches of the 2018 FIFA World Cup in Russia. The study also verifies the theoretical models of soccer players’ physiological parameters. The study sample consisted of 945 observations of 340 players of national teams taking part in the World Cup in Russia. The measured variables included physical activities: total distance covered, distances covered with an intensity of 20–25 km/h, number of sprints; technical activities: number of shots, number of passes, pass accuracy and physiological indicators: evaporative water loss and heart rate. In addition, the final ranking places of each national team were also used in the study. The UTCI was calculated based on meteorological data recorded at training centres and during matches. The UTCI records were then classified into two ranges: NTS—no thermal stress (UTCI 9–26 °C) and TS—thermal stress (UTCI > 26 °C). Climatic conditions at soccer training centres assessed as involving “no thermal stress” are found to be more beneficial for increasing the total distance covered and the number of sprints performed by players during a match. The theoretical models for determining soccer players’ physiological parameters used in the study reduce the players’ heart rate effort and evaporative water loss, which is in line with findings in studies by other authors. The climatic conditions at soccer training centres and during tournament matches should be taken into account in planning preparations for future World Cup tournaments, especially those in hotter countries.

Background The aims of this study were to (1) determine the match technical and running performance required by different teams based on their final ranking position in a professional soccer league; and (2) analyze the correlation between teams’ success at the end of the season and variables related to match technical and running performance. Methods These performance data were collected during a total of 612 matches in the German Bundesliga. The final ranking position and the total of points obtained by each team at the end of the season were registered for the analysis of the correlation between team success and performance. Results The main findings were that there was a significant interaction (p r > 0.7; p ≤ 0.01) with the total of points obtained at the end of the season. Conclusions Strength and conditioning coaches may consider these results to develop adequate training strategies, which may not only optimize performance but also reduce the injury risk.

Background Physical fitness optimization and injury risk-reducing require extensive monitoring of training loads and athletes’ fatigue status. This study aimed to investigate the effect of a 6-month training program on the training-related stress indicators (creatine kinase – CK; cortisol – COR; serotonin – SER; brain-derived neurotrophic factor – BDNF) in youth soccer players. Methods Eighteen players (17.8 ± 0.9 years old, body height 181.6 ± 6.9 cm, training experience 9.7 ± 1.7 years) were blood-tested four times: at the start of the preparation period (T0), immediately following the preparation period (T1), mid-competitive period (T2), and at the end of the competitive period (T3). CK activity as well as concentrations of serum COR, SER and BDNF were determined. Training loads were recorded using a session rating of perceived exertion (sRPE). Results Statistical analyzes revealed significant effects for all biochemical parameters in relation to their time measurements (T0, T1, T2, T3). The statistical analyzes of sRPE and differences of biochemical parameters in their subsequent measurements (T0–T1, T1–T2, T2–T3) also demonstrated significant effects observed for all variables: sRPE (HKW = 13.189 (df = 2); p = 0.00), COR (HKW = 9.261 (df = 2); p = 0.01), CK (HKW = 12.492 (df = 2); p = 0.00), SER (HKW = 7.781 (df = 2); p = 0.02) and BDNF (HKW = 15.160 (df = 2); p < 0.001). Discussion In conclusion, it should be stated that the most demanding training loads applied in the preparation period (highest sRPE values) resulted in a significant increase in all analyzed biochemical training stress indicators. The reduction in the training loads during a competitive period and the addition of recovery training sessions resulted in a systematic decrease in the values of the measured biochemical indicators. The results of the study showed that both subjective and objective markers, including training loads, are useful in monitoring training stress in youth soccer players.

The aim of this research is to evaluate marathon performance and asses the influence of this long-distance running endurance exercise on the changes of muscle stiffness in recreational runners aged 50 + years. Thirty-one male long-distance runners aged 50–73 years participated in the experiment. The muscle stiffness of quadriceps and calves was measured in two independent sessions: the day before the marathon and 30 min after the completed marathon run using a Myoton device. The 42.195-km run was completed in 4.30,05 h ± 35.12 min, which indicates an intensity of 79.3% ± 7.1% of HRmax. The long-term, low-intensity running exercise (marathon) in older recreational runners, along with the low level of HRmax and VO2max showed no statistically significant changes in muscle stiffness (quadriceps and calves). There was reduced muscle stiffness, but only in the triceps of the calf in the dominant (left) leg. Moreover, in order to optimally evaluate the marathon and adequately prepare for the performance training programme, we need to consider the direct and indirect analyses of the running economy, running technique, and HRmax and VO2max and DOMS variables. These variables significantly affect the marathon exercise.

Dariusz, M, Krzysztof, M, Paweł, C, Edward, S, Marek, K, Tomasz, S, Dorota, B, Rektor, Z, and Jan, C. Effects of plyometrics training on muscle stiffness changes in male volleyball players. J Strength Cond Res 33(4): 910-921, 2019-We investigated whether 6 weeks of specific plyometric training (PT) impacts on changes in muscle stiffness and enhances the vertical jumping ability as the indirect evaluation of the explosive power of the lower extremities of male volleyball players. Sixteen male collegiate volleyball players participated in this experiment. Regular PT was performed twice per week for 60-90 minutes each time. During each PT session, heart rate and muscle stiffness data were collected. Two series of 10 single measurements of each muscle (23 points of the front and back legs) were measured the day before the first enhanced training session and after completing each week of PT. Participants were tested for maximum effort in vertical jumping using the squat jump (SJ) with hands on thighs, countermovement jump (CMJ), and CMJ with a 2-step to 3-step approach. Jumping motor ability tests were completed. Data were collected 1 day before PT. The last measurement was performed 3 days after completing the last week of PT. The 6-week PT program only had an effect on the statistically relevant increase in muscle stiffness in the tibialis anterior (highest value, 593.86 ± 60.24 N·m) and quadriceps. Improvements in the explosive power of leg muscles resulted in a significant increase in the vertical jumping ability; there were improvements in SJ and CMJ (p = 0.0338 and p = 0.0007, respectively). If PT involves a moderate workload and if players never exceed the intensity target of the workout, then less muscle stiffness and muscle soreness may occur.

The purpose of the study was to examine how various playing positions affected the number of (and percentage breakdowns for) physical and technical activities of soccer players in the Germany’s Bundesliga. A further objective was to identify and present features distinguishing between the activities of players within the Defender, Midfielder and Forward formations. The study sample comprised 4426 individual match observations of 473 soccer players competing in the Bundesliga during the 2016/2017 domestic season. Data from the Impire AG motion analysis system, and the so-called ”heat maps” it supplies, revealed areas in which players spent most time during a match, with 22 different playing positions on the pitch identified in consequence. Players in the formation comprising Defenders did not differ significantly in relation to the number of accelerations, the number of shots or the percentage of duels won. Furthermore, there were no significant differences among Midfielders in regard to total distance covered, mean running speed, the number of accelerations, the number of duels and the percentage of duels won. Likewise, Forwards did not differ in distances covered at ≥24 km/h, average running speed, the number of sprints, the number of shots, the proportion of on-target passes, the number of duels, or the percentage share of duels won. Irrespective of the formation or position on the pitch, today’s game of soccer also pays great importance to the number of accelerations, as well as the number of duels engaged in, and their effectiveness.

The purpose of this study was to examine how the four best teams in the 2018 Football Men's World Cup rotate by squad and how this impact the physical activity of the teams in consecutive rounds. The study sample consisted of the 31 players of the 4 best teams, who played in every tournament match, except for the third game of the group stage. The analysis included 186 observations and was carried out on the most exploited players (MEP) excluding goalkeepers, who played at least 450 mins (5 full matches) in the tournament. The analysis was conducted using data collected by an advanced motion analysis system known as STATS®. The selected physical activity parameters analyzed included: total distance covered (m/min), distance covered at various intensity ranges (m/min), top speed (km/h), and number of sprints performed. It was found that all four teams in the third match of the group stage have performed the largest number of rotations with most exploited players and introduced the highest number of rested players (7.75 ± 2.06). A significant increase was observed between the second and fourth match in the 0–7 km/h distance covered (37.99 ± 3.19–39.23 ± 3.35 m/min) and the top speed (28.12 ± 2.22–29.21 ± 2.64 km/h)—p < 0.05. Furthermore, MEPs in the knockout stage, used pacing strategies by increasing the amount of low-intensity running to maintain high intensity during the game. From a practical point of view, this investigation shows that squad rotation can be a valuable support to a pacing strategy by players.

This study aimed to examine whether the physical and technical activities of soccer players and match locations can be associated with higher or lower odds of winning matches whose outcome can be described as “close.” The study comprised 7972 individual observations of German Bundesliga players during the 2014/2015 (n = 2794), 2015/2016 (n = 2494), and 2016/2017 (n = 2684) seasons. A selection of “close matches” was made, which were defined as those in which the difference in numbers of scored goals was ≤1. Players’ five pitch positions were considered: central defenders, fullbacks, central midfielders, wide midfielders, and forwards. Data on 12 physical and 10 technical activities performed by players during matches as well as on match location were retrieved from the Impire AG (Germany) match analysis system. The study results show that the odds of winning at home are different for each playing position: from 41.99% for wide midfielders to 91.34% for central midfielders. Another conclusion was that one of the key components of the predictive model for forwards is the percentage of overall distance covered at speeds >24 km/h (7.99%), which is a variable with an increasing trend. The proposed model predicts that each 1% increase in this variable will theoretically be associated with a 4.08% raise of the odds of winning in further seasons. The presented statistical model may be used by trainers to identify players’ physical and technical activities and contextual variables that may significantly affect the match outcome. In addition, it can help to determine the individual training load related to the player’s position on the pitch.

The purpose of this study was to ascertain the effect of playing three consecutive matches with extra time (ET) on the physical performance of selected Croatian players in their subsequent match, the final of the 2018 Men’s World Cup in Russia. The case study consisted of 4 players on the Croatian national team (16 observations) who had played in all three matches up to 120 min. The consecutive full time matches (90 minutes) and extra time (30 minutes) were compared. The analysis was conducted using data collected by an advanced motion analysis system known as STATS and from interviews with the strength and conditioning coach of the Croatian national team. The recorded variables used were: total distance covered [m], distances covered [m] at intensity ranges of 20–25 km/h and above 25 km/h, and number of sprints performed. All the studied parameters systematically increased in each match up to 90 minutes of play, reached their maximum values in the semi-final and then decreased in the final match. Compared to the first extra time period, in the third extra time period the players covered twice as much distance with an intensity of 20–25 km/h and above 25 km/h, and recorded twice as many sprints. This investigation shows that players in central positions on the pitch are able to maintain or even increase high and very high intensity activity in three consecutive matches with extra time. These data complement the developing body of literature relating to the influence of accumulation of match play with extra time periods on high level players.

This study sought to evaluate the hormonal response (i.e. total testosterone, free testosterone, cortisol, and their ratios TT/C and FT/C) in the under-19 youth soccer team (n = 18) throughout a six-month period. All sport medical examinations were conducted four times: before the beginning of the preparation period (T1), just after preparation period (T2), in the middle of the competitive period (T3), and at the end of the season (T4). The cortisol concentration was decreased at the T3 (-16.9%; p = 0.014), then increased at the T2 (16.8%; p = 0.001) and at the T4 (12.7%; p = 0.062), respectively, compared to the initial value. The analyses for total and free testosterone demonstrated no differences between the measurements. Finally, values of the TT/C and FT/C ratios were increased during the T3 (25%; p = 0.017, 24.4%; p = 0.021) in comparison with the initial measurement and decreased at the T4 (-28.9%; p = 0.001, - 30.8%; p = 0.001) in comparison with the T3. The study results showed that the lowest level of peripheral fatigue was recorded in the T3, which may suggest that a correct selection of training loads does not affect the severity of catabolic processes in youth players.

Background Cardiovascular safety of marathon running in recreational runners remains unclear. We set up this study to comprehensively evaluate the effects of a marathon run on the profile of cardiovascular stress biomarkers in connection with transthoracic echocardiography. Design and methods Thirty-three healthy male amateur runners, aged ≥50 years (mean age 57 ± 7) were enrolled. Venous blood samples were obtained before the marathon, just after the race, 2–4 and seven days after the marathon. Using novel single molecule counting technology we measured: plasma concentrations of high-sensitivity cardiac troponin I (hs-cTnI) and endothelin-1. N-terminal pro B-type natriuretic peptide was measured using electrochemiluminescence. Each participant had transthoracic echocardiography before and immediately after the race. Results We observed a sharp rise in the levels of all biomarkers after the race (all p 169 km/month, a median for the studied group) had lower hs-cTnI leak after the race (median 15.11 ng/ml and 31.2 ng/ml, respectively; p Conclusions Marathon run is associated with sharp and significant rises in the biomarkers of cardiovascular stress. The profile of these changes, however, along with echocardiographic parameters, does not suggest irreversible myocardial damage.

The study aimed to examine the performance frequency of selected technical activities by soccer teams playing in the UEFA EURO 2016 in relation to match outcome and match status. Thirty-six matches...

Introduction . Monitoring muscle stiffness in athletes can be a good method of assessing fatigue caused by high training loads, and the early detection of fatigue can help prevent the occurrence of micro-trauma in the muscles that can cause contusions. The research carried out by Wilson et al. [1] confirmed that an optimal level of muscle stiffness is significantly correlated with high muscle loads. The aim of the current study was to determine changes in muscle stiffness of the left and right thighs during six weeks of plyometric training (PT) in volleyball players. Material and methods . The study involved 16 volleyball players from the second-league Opole University of Technology Club (age = 21.12 ± 1.66 years, height = 191.62 ± 5.73 cm, and weight = 86.25 ± 6.66 kg) with at least five years of competitive experience (7.5 ± 2.44 years). Muscle stiffness was measured during three stages of the plyometric training using a MYOTON PRO device (Estonia). Results . An RM-ANOVA analysis showed a significant difference in the resting stiffness of the semitendinosus (posterior thigh) muscles of the left and right limbs before the plyometric training began, but no significant differences were found in the stiffness of these muscles in the fourth or sixth weeks of training. The results of the measurement performed for the anterior muscles of the thigh did not reveal a significant difference in the stiffness of the left limb compared to that of the right limb in subsequent weeks of training. Conclusion . The loads used in plyometric training in volleyball players caused a decrease in the differences in muscle stiffness between the left and right limbs, and in both limbs, adaptation trended towards an increase or a decrease in stiffness.

This study aimed to investigate the relationship between the climatic conditions predicted for the 2022 FIFA World Cup in Qatar and the capacity for repeated maximum effort (RSA), of soccer players. Twenty-four semi-professional soccer players participated in the study. The exercise test consisted of ten 6-second maximal efforts on a cycloergometer. A 90-second passive rest interval was used. Mechanical parameters were recorded in each repetition, and biochemical parameters at rest and even repetitions. The test was performed in a Weiss Technik WK-26 climate chamber under two different conditions: (1) thermoneutral (TNC - 20.5 °C; 58.7% humidity); (2) predicted for the 2022 World Cup in Qatar (QSC - 28.5 ± 1.92 °C; 58.7 ± 8.64% humidity). Significantly higher mean maximum power values were recorded in the second repetition under QSC conditions (1731,8 ± 214,4 W) (p = 0.025). A significantly longer time to reach maximum power was also recorded under TNC conditions compared to QSC conditions in repetition 2 (1,32 ± 0,33 s), (1,05 ± 0,29 s) (p = 0.016) and 6 (1,41 ± 0,48 s), (1,17 ± 0,25) (p = 0.036). There was a significantly higher rate of power loss, between repetition 2 (p = 0.023) and 4 (p = 0.043) under QSC conditions, compared to TNC. Considering the biochemical parameters, a significantly higher pO2 concentration was registered under QSC conditions in the 10th repetition (p = 0.006). The ambient temperature during exercise should be taken into account to determine the anaerobic exercise capacity of the athletes. At higher temperatures, there is a greater capacity for maximal effort, in terms of maximal power achieved, but with a greater decrease in performance.

The aim of this study is to determine synergistic motor outcomes understood as sets of mutually dependent players’ motor abilities affecting the efficacy of performance skills of young volleyball players. The study was carried out during a national volleyball tournament for 150 boys aged 14-15 years. The matches were recorded with two cameras placed 10 m behind the end line, 1.6 m above the floor. The following parameters were assessed: attack efficacy, block efficacy, serve efficacy. The first dependent variables were players' actions that most significantly affected the set outcome, i.e. serves, blocks and attacks. The greatest differences were found among players' serve results, where – with the exception of ineffective serves – the index of variability ranged from v = 67.14 (counter-effective serve) to v = 80.23 (effective serve). The study showed that serving and attacking effectiveness is directly determined by standing jumping ability, while blocking efficacy is affected by the height of the running vertical jump.

Introduction. Having possession of the ball makes it possible for the players of a team to undertake a greater number of actions that can help the team win the match. The aim of the current study was to determine the number and completion rate of passes made from different distances in relation to percentage ball possession and the outcome of the match in the group stage of the FIFA World Cup held in Brazil in 2014. Material and methods. The study included 32 teams who participated in the final tournament. The performance of 266 players (682 observations) who played 48 matches in the group stage was examined. Only players who took part in the entire match were included in the research, and goal-keepers were excluded. The data used in the study, which had been recorded by means of the Castrol Performance Index system, were obtained from the FIFA official website. The total number of passes and the percentage of completed passes were analysed, which were classified as short, medium, and long, in relation to the team’s percentage possession of the ball (over and below 50%) and the outcome of the match (win, loss, or draw). Results. Out of the three types of passes which were examined in the study, teams playing in the World Cup in Brazil most often made medium passes. The number of these passes was the highest in matches won. These matches were also characterised by a significantly higher percentage of completed long passes. Conclusions. Players from teams who were in possession of the ball more than 50% of the time performed a higher number of all types of passes, regardless of the outcome of the match. The completion rate for these players was significantly higher only for short and medium passes.

The study aimed to: (1) investigate physical and technical performance among players during six consecutive phases of a competitive season, (2) determine if levels of match running and technical performance between the 1st and 6th phases of a season can be maintained, (3) and determine which phase features the lowest and highest values for variables assessed. Seventy out of 556 outfield players who played at least 80% of the matches in each phase of the Bundesliga seasons were analysed. Each season was divided into 6 phases: phase 1 (matches 1&ndash, 6), phase 2 (7&ndash, 11), phase 3 (12&ndash, 17), phase 4 (18&ndash, 23), phase 5 (24&ndash, 28) and phase 6 (29&ndash, 34). Thirteen variables were selected to quantify the physical and technical activity of players. Our results showed that by reducing the distances covered at intensities below 11 km&middot, h&minus, 1, players were able to cover greater distances at intensities in the range of 11&ndash, 13.99 and 21&ndash, 23.99 km&middot, 1 in subsequent phases of a season. Players&rsquo, capacity to maintain match running and technical performance between the first and sixth phases of the season has been demonstrated, though the 4th phase of the season showed a breakthrough point as regards the maintenance of exercise capacity among players participating in the Bundesliga.

Background The aim of this study was to determine what physical and technical activities of soccer players in different pitch positions affect significantly the match outcome of professional German soccer players; as well as to examine whether differences in physical and technical activities increase or reduce the probability of a match being won. Methods The study sample comprised 4393 individual match observations of 350 soccer players competing in the Bundesliga during the 2014/2015 domestic season. Analysis was confined to outfield players (other than goalkeepers) who completed entire matches, and was carried out using the Impire AG motion analysis system. The selection of physical and technical activities to be used in predictive models was achieved using the lasso method. Results The odds ratio revealed that an mean running speed in the second half that was greater by 0.1 km/h was associated with a 27.0% improvement in the odds of a match being won (OR=1.27; 95% CI: 1.17 to 1.38) (forwards), 15.7% (OR=1.16; 95% CI: 1.09 to 1.23) (wide midfielders), and 10.0% (OR=1.10; 95% CI: 1.04 to 1.17) (central midfielders). Furthermore, in the case of wide midfielders, a significant variable was the distance covered at >24 km/h, with an increase of 0.1 km associated with odds of winning the game improved by 31.7% (OR=1.32; 95% CI: 1.05 to 1.66). Conclusions Match outcome is affected significantly where peak and mean running speeds in the second half of the match are greater, and where longer distances are covered at speeds in excess of 24 km/h.

The study aimed to assess the total covered distance during a match, performance volume below and above the anaerobic threshold, as well as characterize physical activities of professional Bundesliga goalkeepers during soccer matches. 34 goalkeepers (606 observations) from all eighteen Bundesliga teams, who played in the 2014/2015 season were considered for the study. The performance of goalkeepers was analyzed with the use of the VIS.TRACK system. The variables measured included: total covered distance [km] in the whole match, the first half, and the second half; distance covered below and above the anaerobic threshold (4 m • s–1) [km]; and distance covered in six intensity ranges [km]. The total distance covered by the goalkeepers was 5.48 ±0.56 km. The distance covered by goalkeepers below the anaerobic threshold was 5.28 ±0.52 km, whereas the distance covered above the anaerobic threshold amounted to 0.21 ±0.09 km. The ratio between the goalkeepers’ volumes of aerobic and anaerobic performance was 25:1. The total distance covered by goalkeepers in match play and the distances covered by goalkeepers below and above the anaerobic threshold (96.17% and 3.83%, respectively) indicate that during a match the goalkeepers undertake predominantly aerobic exercises.

The study assesses the effects of a six-week plyometric training program (PT) on muscle stiffness in the dominant and non-dominant leg in male collegiate volleyball players. The study group comprised 16 volleyball players who had played collegiate volleyball for at least four years. For six consecutive weeks, twice a week, the players undertook a plyometric program of 60-min training sessions, each preceded with a specialist warm-up. The analysis of the anterior muscles of the right and the left lower leg revealed a significant increase in stiffness in the muscles of the right leg and the left leg. No significant differences were found between the anterior muscles of the left lower leg and the right lower leg in particular weeks of the training program. The analysis of the posterior lower leg muscles revealed no significant differences, either in the consecutive weekly training microcycles or between the left leg and the right leg. The measurement of muscle tone and biomechanical properties of muscles can be used as a fast and direct assessment of plyometric training-related muscle fatigue. A similar level of muscle stiffness in both lower legs (symmetry) is a reflection of the appropriate selection of plyometric training loads.

The aim of the present study is to examine how various playing positions and end result (i.e. won, drawn or lost match) affect the total covered distance and distances covered at low and high-inten...

The aim of the present study was to determine and characterize the activity of male Polish Premier League soccer players during elite-level matches, depending on playing position, activity intensity range, and match period. The study sample comprised 1178 players. Amisco Pro® was used to track the match activity players. Statistical analysis of the total distance covered by players revealed that the greatest distance was covered by central midfielders (11894 ± 765 m) and external midfielders (11751 ± 686 m). In terms of velocity, the greatest distance was covered by players in the V1 range (0 ≤ V1 11 km · h

This study presents a detailed analysis of sprinting activities and distance covered by professional soccer players in two seasons of the Europa League competition. The investigation considered such variables as the mean sprinting distance covered, duration of the rest pause between sprinting activities and maximal running speed recorded during the match. The study involved 147 soccer players participating in 10 matches played at one ground in the 2008–2009 and 2010–2011 Europa League seasons. Players' performance data were divided into two halves of matches and five playing positions. The study was carried out using data from Amisco Pro (version 1.0.2.). Results indicate wide variations in the analyzed variables, depending on the playing position on the pitch and tactical tasks. Individualization of training speed and endurance loads will help to optimize the training process of soccer players at different levels of their athletic skills.

The aim of the present study was the analysis of match activities of full-backs from selected European national soccer leagues. The study sample comprised 30 full-backs playing in the autumn round of the 2014/15 season from five European national top-tier leagues: English Premier League, Spanish Primera Division, German Bundesliga, Russian Priemjer Liga and Italian Serie A. The performance of full-backs (left-back and right-back) from each selected team was analyzed using a professional match analysis system OptaPro which tracks every possible type of ball touch and on the ball action in match covered by a rigid set of definitions. The data for analysis included the total number of passes, total number of crosses, and total number of ball touches performed by the fullbacks in three zones of the pitch: attack, midfield and defense. The study results showed that the full-backs from the Spanish Primera Division executed the highest number of passes and crosses as well as ball touches in the attack zone. They also performed the lowest number of passes in the midfield and defense zones, in which the highest percentage of passes was achieved by the full-backs from the German league teams. The study indicates that in modern soccer defenders must possess a high level of offensive skills that can be necessary in the last stage of a team’s attack.

Our aim was to verify whether running a marathon is associated with changes in irisin concentration in healthy, endurance-trained men. In an observational study, we assessed baseline biochemical and fitness parameters of 28 middle-aged runners (mean ± SD age, BMI, VO2max: 58 ± 8 years; 24.5 ± 3 kg/m2; 51.1 ± 1.7 ml/kg/min). We evaluated irisin before, immediately after, and 7 days after the marathon. Irisin concentration decreased from a baseline value of 639 ± 427 to 461 ± 255 ng/ml immediately after the marathon (p

Background This study aimed to investigate the effect of a 6-week plyometric exercise training program on the development of lower limb explosive power in terms of vertical jumping ability in university level volleyball players. The study involved 9 male volleyball players from the AWF Wroclaw University Sports Club, with a minimum of 5 years of training and competition experience. The program consisted of various bounds, hops, and jumps in vertical, horizontal, and mixed directions. During the program, a progressive overload of plyometric intervention was applied. Lower limb explosive power in the form of vertical jumping ability was developed and tested. Methods The jumping ability was evaluated via 5 types of maximum-effort vertical jumps, using the Opto Jump system. In addition, once each week, the heart rate was recorded using a heart rate monitor (Polar RS300X GPS). Results The only significant correlation was found between squat jump and number of jumps and between counter movement jump and heart rate. Conclusions From a practical standpoint, the improvement, which was noticed after 3 and 6 weeks, seems to optimal period for volleyball players adaptation to significant increased training load.

BACKGROUND The aim of the study was to examine the ways playing positions and match outcome (i.e. win, draw, loss) affect the sprint distance covered and the number of sprints performed by German Bundesliga soccer players. METHODS Match performance data were collected from 350 soccer players competing in the German Bundesliga during the 2014/2015 domestic season. A total of 4393 individual match observations were undertaken on outfield players. The analysis was carried using the Impire AG motion analysis system with records of all movements of players in all the 306 matches. The recorded variables included total sprint distance covered and the total number of sprints in offensive and defensive play. The conformity assessment was carried out with the Shapiro-Wilk test (P≤0.01). To compare mean values of the examined variables a two-way ANOVA was used. The differences between pairs of means were verified with Fisher's LSD. RESULTS The analysis of the covered sprint distance and the number of performed sprints showed that central defenders and full-backs covered shorter distances in won matches than in lost matches (P≤0.05). Furthermore, forwards and wide midfielders covered significantly longer sprint distances in won matches than in lost matches (P≤0.05). CONCLUSIONS The match outcome may be viewed as a measure of performance accomplishment and, hence, it may influence the sprinting efforts made by players.

The aim of this study was to investigate soccer players’ recovery by analyzing activity profiles of 11 Polish professional league soccer players over a period of three intense matches. Activity pro...

The aim of this study was a detailed physical and technical activities analysis of professional soccer players. The studied match performance variables included physical activity and technical acti...

The aim of this study was to determine relationships between repeated 1 &times, 1 small-sided games (SSGs) (variable duration, constant work-to-rest ratio) and the concentration of steroid hormones and characteristic fatigue markers in youth soccer players. Eighteen young male soccer players were assigned at random to two experimental groups: E1&mdash, undertaking a six 30 s one-on-one SSGs with a 2 min rest period, and E2&mdash, playing six 45 s SSGs with a 3 min rest interval. Capillary blood was collected from the players at rest, after the last game, and 15 and 30 min after the exercise protocol. The variables assessed included serum cortisol (C), free testosterone (FT) and total testosterone (TT). An effect was observed between the measurement times (TT (F = 15.26, p &le, 0.0001), FT (F = 6.86, p = 0.0006)). In terms of cortisol (C) levels, no interactions or effect between the studied groups were revealed, but an interaction was found (F = 4.01, p = 0.0126) and the effect appeared between the measurement times (F = 11.16, p &le, 0.0001). The study results show that in all likelihood, longer rest intervals in repeated 30 s 1 &times, 1 SSGs can reduce catabolic reactions and hence the risk of overtraining in youth soccer players.

The aim of the study was a detailed analysis of the sprinting activity of professional soccer players. The study involved 147 players who played in 10 matches of the 2008-09 and 2010-11 UEFA Europa League seasons. The number of performed sprints and total sprint distances covered by the players were examined using collected statistical material. Two types of sprints were distinguished based on their duration: S, short-duration sprint (below 5 seconds) and L, long-duration sprint (above 5 seconds). Additionally, sprints were classified according to their distance: 0-10, 10.1-20.0, and >20 m, respectively. The analysis of the sprinting activity of soccer players also involved their respective positions of play. The study was carried out using Amisco Pro (version. 1.0.2), one of the most comprehensive up-to-date computer systems for match analysis. The statistical analysis revealed that the mean total sprint distance covered by players (≥24 km·h) amounted to 237 ± 123 m. With regard to the position of play, the forwards covered the longest sprint distance (345 ± 129 m), that is, 9% longer than midfielders (313 ± 119 m) and over 100% longer than central midfielders (167 ± 87 m). The average number of sprints performed by the soccer players was 11.2 ± 5.3. It should also be emphasized that about 90% of sprints performed by professional soccer players were shorter than 5 seconds, whereas only 10% were longer than 5 seconds. Analysis of physical loads of soccer players during matches can be useful for individualization of training of soccer players' speed capabilities. It is an essential instrument of modern planning and application of training loads.

The aim of this study was to evaluate the changes in pressure pain sensitivity maps in untrained subjects over 2 subsequent sessions of eccentric exercise (ECC) expected to result in (a) delayed onset muscle soreness (DOMS) and (b) adaptation/recovery, respectively. Eleven healthy male subjects participated in this study. Pressure pain threshold (PPT), rate of perceived exertion (RPE), pain intensity, soreness area drawing, maximal voluntary contraction (MVC), and shoulder range of motion were assessed in session 1 before, immediately after, and 24 hours after ECC. The ECC protocol that was used to induce DOMS consisted of 50 eccentric contractions of the right shoulder that were divided into 5 bouts, including 10 contractions at MVC level separated by a 2-minute resting period. Session 2 was identical to session 1 and performed exactly 1 week later. There was only a significant increase in the RPE assessed before the exercise and 24 hours after the exercise in session 1 (p = 0.001). The average PPT only decreased significantly from before the exercise (660.2 ± 76.2 kPa) to 24 hours after the exercise (435.6 ± 59.3 kPa) in session 1 (p = 0.016). The present study confirmed a heterogeneous distribution of mechanical sensitivity before and after sessions of ECC. The first session of ECC underlined increased mechanical sensitivity because of DOMS, whereas the second session reflected an adaptation process. Our results support the potential role of ECC bouts in training regimens.

The objective of this study was to determine the distance covered by professional soccer players during matches with the use of the computerized match analysis system Amisco Pro® (version 1.0.2, Nice, France). Kinematic examination included the specification of the distance covered by 31 players participating in 4 matches in the Union of European Football Association Cup competitions during the 2008-2009 season. Data were analyzed based on players' positions on the pitch, changes in the players' motor activity intensity level, and match period (first or second half). The results of statistical analysis revealed that the average total distance covered by all players (n = 31) was 11,288 ± 734 m. With respect to the player's position on the pitch, the midfielders traveled the longest average distance (11,770 ± 554 m) during the game. This was 3% longer than the distance achieved by the attackers at 11,377 ± 584 m, and 7% longer than that achieved by the defenders 10,932 ± 728 m. The analysis of physical loads on soccer players during a match is highly useful for training individualization. It provides a tool for effective planning and for recording the loads on players, which is an indispensable element of modern coaching.

Eleven healthy volunteers took part in three sessions where computer work was performed for 10 min in each session. The recordings were made on two consecutive days. After the first session, the subjects underwent a series of high intensity eccentric exercises of shoulder elevation to induce muscle soreness. The second session was performed immediately after the exercises and third session 24 hours after the exercise. Surface electromyography (EMG) of descending and ascending trapezius, deltoideus anterior and serratus anterior was recorded. Exposure variation analysis (EVA) centroid and marginal distribution was computed. Principle component analysis (PCA) was performed on both cases. Describing more than 80% of variance, first eight components for EVA marginal distributions and first four ones for EVA centroid were picked to be investigated. The sole EVA amplitude levels played a practically significant role to describe the variation in EVA marginal distribution. However, a significant pattern of load redistribution to superficial muscles was not found. This may suggest investigating the role of deep muscles in redistribution of load during computer work in response to high level eccentric contractions.

During aerobic exercise with increasing intensities choice reaction time (CRT) progressively shortens up to 60-80% of maximal workload, and then it rapidly increases. The aim of this study was to determine whether workload associated with the shortest CRT operationally called "the psychomotor fatigue threshold" is related to the metabolic response to exercise. Thirteen male soccer players (aged 23.3 + or - 1.0 yrs) participated in this study. Before and after 6 weeks of training in the pre-competition period they underwent treadmill test at 0 grade with running speed increasing every 3 min by 2 km/h starting from 6 km/h until exhaustion. At each stage of exercise CRT, heart rate, respiratory gas exchange and blood lactate [LA] were measured and the workload corresponding to [LA] of 4 mmol/l (OBLA) was recorded. After training, CRT was significantly shortened at rest (from m + or - SEM = 345 + or - 12 to 317 + or - 12 ms) and during exercise (from 304 + or - 10 to 285 + or - 11 ms at the psychomotor fatigue threshold and from 359 + or - 13 to 331 + or - 13 ms, p

Aerobic capacity and sprint velocity of Leagues I and IV football players Study aim: To assess the aerobic capacity, sprint velocity and changes in biochemical variables in football players preparing for the spring round of matches. Material and methods: Football players from League I (n = 19) and League IV (n = 15) were subjected twice to a graded running tests at the beginning and at the end of the pre-season preparation period. The following variables were recorded: maximum running velocity (km/h), O2max (ml/kg/min), pulmonary ventilation (VE), load at the lactate threshold (LT) expressed as the threshold velocity (LTV; km/h) or %O2max, activities of enzymes in plasma - creatine kinase (CK) and lactate dehydrogenase (LDH), concentrations of lactate (La), ammonia (NH3) and of glucose (Gl) in plasma. At the end of the study the players were also subjected to a 30-m sprint test. Results: In League I players, LT significantly (p3 and Gl significantly (p Conclusions: The negligible differences between football players from Leagues I and IV in their aerobic capacity and speed abilities, and the marked distance from world elite players in those indices, call for substantial changes in training strategies and schedules.

Individualization of Physical Loads and Speed Abilities of Young Soccer Players in a Six-Month Training Macrocycle The aim of this paper was to address the issue of individualized training loads and its influence on speed development among speed-type and endurance-type players during a six-month training macrocycle. The research was conducted in a group of 36 young male soccer players from for two sport clubs: Lech Poznań and Warta Poznań. The stages of the study undertaken resulted from the time structure of sport training and were carried out during a six-month macrocycle. The players of Lech Poznań took part in a test which involved applying three series' (six repetitions each) of speed-type exercises, with regard to the player's motor type in each of the three training units comprising the weekly macrocycle. During each stage of data collection, the players were subjected to a stress test for stretches of 10, 20 and 30 m. The study has shown a significant impact of individualization of training loads on development of speed abilities in the examined players. An increase of speed during the tests of 10 and 20 m was noted in both speed and endurance-type players. This was probably an effect of adapting individual training loads to motor predispositions of the players during the six months of the experiment. It can be also assumed that the increase in speed among the subjects is a result of rising phosphagen potential and enzymatic activity (especially creatine kinase), as well as improved motor units recruitment.

Evaluation of the Blood Antioxidant Capacity in Two Selected Phases of the Training Cycle in Professional Soccer Players The aim of this study was to evaluate the effects of a regular pre-season training on the aerobic performance and the blood antioxidant defense capacity in soccer players from the Polish Premier League club (n=19) and IVth League team (n=15). The players participated in an incremental treadmill running exercise to volitional fatigue twice (i.e., at the beginning (Trial A) and the end (Trial B) of the pre-season spring training). In venous blood samples, taken at rest and 3 min post-test, the activities of antioxidant enzymes (SOD, GSH-Px, CAT, GR) and concentrations of non-enzymatic antioxidants (GSH, tocopherols, retinol, uric acid) and malondialdehyde as a lipid peroxidation biomarker were measured. With the aim of between-group comparisons and possible conclusions on training-induced changes in the capacity of the blood antioxidant defense, the POTAX index was calculated as a sum of standardized activities of antioxidant enzymes and concentrations of non-enzymatic antioxidants. The results of the present study indicate that the players from the Premier League club were characterized by only slightly higher maximal oxygen uptake rates, the differences compared to IVth League team, as assessed in both trials, were statistically insignificant. Participation in the pre-season training resulted in a moderate improvement of aerobic performance, although only a few players were characterized by VO2max comparable to the international-class elite performers. No distinct differences were observed in the level of aerobic performance between higher- and lower-classified players. Pre-season training led to an improvement in the global blood antioxidant capacity expressed in terms of POTAOX indices, although the changes in the activities and concentrations of individual components of the antioxidant system were less pronounced. Training-induced level of antioxidant conditioning was higher among the Premier League players, which may be related to differences in the training schedule and nutritional preparation of the athletes.

The aim of the study was to investigate the effects of breath-hold diving on divers' psychomotor performance and blood adrenaline, noradrenaline and lactate concentrations. Four male divers took part in the experiment. During the study the divers' choice reaction time as well as plasma concentration of adrenaline, noradrenaline and lactate were measured. The measurements were carried out before immersion (before a warm-up), three minutes after the dive, and 60 minutes after the dive. A reduction in the reaction time to audiovisual stimuli was found in three divers, three minutes after the dive. Diver 4, who broke his personal best record, had a longer choice reaction time at three minutes after the dive. The adrenaline concentration was lowered in Diver 1 and Diver 2, at three minutes after the dive. The adrenaline level in Diver 3 was relatively steady at all test measurements. In Diver 4, who broke his personal best, a twofold increase in adrenaline concentration was noted at three minutes after the dive. All examined divers revealed an increase in noradrenaline blood level at three minutes after the dive. The results of the study are of great practical value since disturbed reactions during freediving can put the diver at the risk of serious barotraumas.

Rationale: The effects of caffeine on psychomotor performance have been evaluated under resting conditions and in a thermoneutral environment. Our hypothesis was that these effects could be modified by factors enhancing the level of alertness, such as exercise and cold exposure. Objective: The purpose of this study was to follow up changes in the multiple choice reaction time (RT) during exercise at room and low ambient temperatures after caffeine or placebo administered in a double blind manner. Methods: Nine soccer players performed multistage, incremental exercise until volitional exhaustion on a bicycle ergometer at 22°C or 4°C, 1 h after ingestion of coffee with caffeine (CAF) or without it (PL). Immediately before exercise and at the end of each workload, RT and blood lactate (LA) were measured. Oxygen uptake (VO2) and heart rate (HR) were recorded continuously. Blood LA threshold and the workload associated with the shortest RT were determined. Results: During exercise at 22°C, RT was significantly shorter in CAF than in the PL test, while at 4°C there were no differences in RT between CAF and PL trials. Cold exposure did not affect RT either at rest or during exercise. Neither caffeine nor cold exposure influenced the maximal VO2, the maximal HR and LA threshold. Conclusion: In the thermoneutral environment, caffeine ingestion improved psychomotor performance during exercise, whilst at low ambient temperature this effect was blunted. These findings suggest that the stimulating action of caffeine depends on the level and source of arousal.