The characteristics of counterattacks in the Spanish league (La Liga) in 2021-2022.

BACKGROUND: Current studies on counterattacks are limited despite the fact that it is one of the most effective ways to score in soccer. The aim of the study was to investigate the characteristics of counterattacks in the Spanish league (La Liga) for the year 2021-2022. METHODS: The sample used in the study were 2631 counterattacks collected from a total of 380 games. The variables used were: 1) the space which the counterattack had started; 2) the number of players who participated; 3) the number of defending players; 4) the duration of the counterattack; 5) the touches to complete the counterattack; 6) the formation of both teams; 7) the way that counterattack was completed (final action); 8) the minute that the counterattack took place; and 9) which team had a home advantage. The results were analyzed using the Chi-square test. The level of significance was defined at P<0.05. RESULTS: Firstly, it appeared that most counterattacks began from the axis of the defensive zone lasting 6-15 seconds. There were 3-4 attackers participating against 4-6 defenders, using 5-9 touches. In addition, most of them took place in the 46-60 minute of the game and were completed in a shot. CONCLUSIONS: The study can help coaches and analysts to understand the characteristics of the counterattacks and adapt their training in a way to make their teams more effective, both in the attacking and defending phase.

Muscle Strength and Joint Range of Motion of the Spine and Lower Extremities in Female Prepubertal Elite Rhythmic and Artistic Gymnasts.

The purpose of this study was to investigate and compare the passive joint range of motion (PROM) and muscle strength in prepubertal rhythmic gymnasts (RGs), artistic gymnasts (AGs), and a control group (CG) of the same age. A total of 54 prepubertal girls were divided into three groups: 18 RGs (age 11.14 ± 0.7, height 142.6 ± 5.81, and body mass 31.2 ± 3.63); 18 AGs (age 11.27 ± 0.99, height 139.6 ± 5.85, and body mass 31.7 ± 3.21), and 18 school girls who are defined as CG (age 10.55 ± 0.42, height 145.33 ± 6.95, and body mass 42.1 ± 8.21) participated in the study. All athletes were elites and participated in national competitions. The CG participated only in their school physical education program. Isokinetic peak torques were measured using an isokinetic dynamometer (Cybex II) at 60, 180, and 300°·sec-1. Body mass index was greater in the CG compared to RGs and AGs (p < 0.001). PROM in cervical extension in RG was significantly higher compared to the AG and CG (p < 0.001). The athlete groups, RG and AG, showed significantly greater PROM in knee flexion (p < 0.001), hip flexion (p < 0.001), and hip abduction (p < 0.05) compared to CG. PROM in hip flexion was different between the left and right leg in RGs. The relative muscle strength of the quadriceps in the RG and AG was significantly greater compared to CG (p < 0.001 and p < 0.01 respectively). Gymnastics training in prepubertal ages can improve neuromuscular function and increase the relative muscle strength. Therefore, it is essential to note that when evaluating children within the developmental ages, especially those involved in sports, the type of muscle strength to be assessed should be specified.

Match Running Performance Profile and Heart Rate Response in Amputee Soccer Players.

INTRODUCTION: The purpose of this study was (a) to create a profile of the running performances of male amputee soccer players in different speed zones, (b) to investigate the relationship between heart rate (HR) and running distance in two soccer matches, and (c) to study the effect of the level of amputation on the running distance covered during a match. MATERIAL AND METHODS: The participants were male amputee soccer players (n = 10, Greek, n = 5; Belgian, n = 5) who played two international, friendly matches. Distances were measured using a global positioning system, and HRs were recorded using a Polar Team Pro. RESULTS: No differences in the distances covered were observed between participants with different levels of amputation (p > 0.05). Nevertheless, there was a trend that participants with a below-the-knee amputation tended to cover longer distances in total (difference +262.3 m, Cohen's d = 0.40) and in zones 2 (+324.4 m, d = 0.79), 3 (+ 7.1 m, d = 0.65), 4 (+22.7 m, d = 0.43), and 5 (+0.4 m, d = 0.20) and less distance in zone 1 (-207.2 m, d = 0.88). They also tended to perform more accelerations (+3.9, d = 0.89) and decelerations (+4.2, d = 0.87) and had a higher mean HR (+8.4%, d = 2.04) than those with an above-the-knee amputation. Moreover, the mean HR corresponded to 83.3% of the HRmax and did not correlate with distance in any speed zone. CONCLUSIONS: It was concluded that the level of amputation might influence running performance and acute physiological response during a soccer match.

Correlations of passes and playing formations with technical-tactical elements during the 2022 FIFA World Cup.

BACKGROUND: This study on the 2022 Qatar FIFA World Cup examined: a) the existence of correlations between passes with other technical-tactical elements, b) the differences in technical-tactical elements in relation to team formation, and c) the characteristics of the key passes created during games. METHODS: Sixty-four games were analyzed. Match-analysis data were collected using InStat database. RESULTS: Spearman correlation revealed that the number of passes and key passes correlated with number of goals, chances and shots (P<0.05). Team ball possession was correlated with number of passes, key passes, chances, shots and the organized attacks (P<0.001). Kruskal-Wallis H non-parametric test revealed that the teams with the higher percentages of team ball possession, and the higher number of chances, shots and crosses used formations 1-4-2-3-1 and 1-4-3-3. Finally, most of the key passes performed in axis of the field and they were short low passes. CONCLUSIONS: The ability of teams to keep the possession of the ball, looking for the key pass, and final action can be a factor in the team's success. A characteristic finding of the study was the preference of groups to manifest their attack from the axis. The equal distribution of attacks between the axis and the sides of the field makes the team's offensive function more unpredictable. Also, most formations concentrate several players on the axis, making it more difficult to complete an attack from this area.

Muscle Strength and Hamstrings to Quadriceps Ratio in Young Soccer Players: A Cross-Sectional Study.

The aim of the present study was to examine and compare the concentric isokinetic peak torque of the knee flexors and extensors muscles, as well as their ratio, in young soccer players. Two hundred and sixty-five (n = 265) young soccer players were divided into five groups: U-12 (n = 43, mean age 11.5 ± 0.4 yrs), U-14 (n = 63, mean age 13.6 ± 0.3 yrs), U-16 (n = 64, mean age 15.4 ± 0.5 yrs), U-18 (n = 53, mean age 17.5 ± 0.4 yrs) and U-20 (n = 42, mean age 19.3 ± 0.6 yrs). Three maximal voluntary isokinetic leg extensions and flexions at angular velocities of 60, 180, and 300°·s-1, and H:Q strength ratio was determined. The largest H:Q strength ratio for all ages, with the exception of age group U-12, appears at a slow angular velocity of 60°·s-1, and the smallest H:Q ratio at a fast angular velocity of 300°·s-1. In age group U-12, at an angular velocity of 60°·s-1, the strength of the quadriceps muscle was almost twice the strength of the hamstrings. The H:Q strength ratio was smaller in age group U-12 and greater in group U-20. In age group U-12, the greatest H:Q strength ratio appeared at an angular velocity of 180°·s-1, while in the other age groups, it appeared at 60°·s-1. Strength training of hamstring muscles remains inadequate across ages. The small H:Q strength ratio in younger ages and the large H:Q ratio in older ages suggest that high-intensity training may increase the H:Q strength ratio, which, in turn, may protect the knee joint from excessive and burdensome loads.

Goalkeepers' plasticity during learning of a whole-body visuomotor rotation in a stable or variable environment.

Postural adjustments performed in anticipation of uncertain visual events is a common sensorimotor control problem in open sport skills. In this study, we examined how expert soccer goalkeepers and non-athletes learn a whole body visuomotor rotation during postural tracking of constant and variable visual target motions. Twenty-one (21) soccer goalkeepers (18 ± 15 years, 75 ± 12 kg) and 25 age-matched non-athletes (18 ± 12 years, 75 ± 15 kg) practiced lateral weight shifting on a dual force platform while tracking the motion of a constant (11 goalkeepers and 12 non-athletes) or a variable (10 goalkeepers and 13 non-athletes) visual target with provision of online visual feedback (VF). After 40s of tracking (baseline), the visual presentation of the VF signal reversed direction relative to the participant's motion (180° visuo-motor rotation) for 60s (adaptation) and then returned to its veridical direction for another 20s (washout). During adaptation, goalkeepers reduced the spatiotemporal error to baseline levels at an earlier time block (3rd block) compared to non-athletes (6th block), but this difference was significant only for groups tracking of the constant and not the variable target motion. Only the groups tracking the constant target increased the spatiotemporal error during the 1st washout block demonstrating a significant aftereffect. It is concluded that goalkeepers adapt faster to the feedback rotation due to their prior field knowledge of relevant visuomotor transformations in anticipation of deceptive visual cues. This expertise advantage however is present only in a stable visual environment possibly because learning is compromised when tracking uncertain motion cues requiring closed loop control.HighlightsWe examined how expert goalkeepers and non-athletes adopt to a novel whole body visuomotor rotation when tracking a constantly or variably moving targetGoalkeepers adopted faster to the visuomotor rotation than non-athletesExpertise related differences were evident only for groups tracking the constant target motionGroups tracking the variable target motion did not learn the visuomotor rotation.

Effects of Combined Horizontal Plyometric and Change of Direction Training on Anaerobic Parameters in Youth Soccer Players.

The aim of this study is to investigate whether the combination of soccer training, plyometric training (PT), and change of direction (COD) exercises would enhance anaerobic performance to a greater extent than training on its own in youth U17 soccer players. Twenty youth players participated in this study. Players were randomly separated into two groups: the control group (CG, n = 9) and the intervention group (EX), which performed extra PT and COD exercises (EX, n = 11). The duration of the training program was six weeks. Sprint 10 m, 30 m, countermovement jump (CMJ), single leg countermovement jump (CMJ right and left), squat jump (SJ), 505 test, and Illinois agility test were measured pre and post of the training program. The performance in the 505 test improved for the EX group (right leg: p = 0.031, left leg: p = 0.004). In addition, Illinois test performance increased in the EX group (2.9%, p = 0.019). The performances of the two groups differed significantly in the Illinois agility test (p = 0.001). This study supports that a short-term combined program of PT and COD exercises can improve change of direction ability in youth U17 soccer players. The lack of effect of the intervention program on sprint and jump performance may be due to the type and volume of plyometric exercises used. The results reflect the training principle of specialization of stimulus. The improvement in performance was presented in tests that had similar characteristics to training stimuli.

Repeated sprint ability in young football players according to the position and formation of the team: the effect of a specific training program.

BACKGROUND: The aim of this study was to investigate the effect of a specific training program for 12-weeks (twice a week) on the repeated sprint ability (RSA), according to the position of the football player in the formation of the team. METHODS: Two groups of U-17 football players (experimental-group, N.=22 and control-group, N.=19) and five positions (central-defenders, wide-defenders, central-midfielders, wingers, and central-attackers) according to the position in the formation (1-4-3-3) were studied. Sexual maturation was classified according to Tanner's stages. RSA and isokinetic strength were measured pre- and after the training program. RESULTS: The results showed that in RSA were differences in the factor time in the best (F=9.316, η2=0.383, P=0.008) and mean time (F=8.002, η2=0.348, P=0.013), but there were no differences between the groups. In strength, differences were observed in the time, mostly in the extensors at the three angular velocities (60°, 180°, 300°·sec-1) with differences in the group only in the maximum force (F=8.090, η2=0.366, P=0.013). No differences between players' positions were observed. CONCLUSIONS: A specific training program seems to affect players' performance on repeated sprint ability and the specific training in the players' position according to the team formation has a positive effect on the muscle power of football players.

Surface Electromyographic Activity of the Rectus Abdominis and External Oblique during Isometric and Dynamic Exercises.

Exercises for the abdominal muscles are widely used in athletic activities for strength training and prevention of low back disorders. The timing and volume of muscle activation for various movements have not yet been clarified. The purpose of this research was to evaluate the surface electromyographic activity from the upper (RAU) and lower part (RAL) of the rectus abdominis and the external oblique (EO) muscles during eleven abdominal muscle strength training exercises. Thirty-five healthy male university students with a subspecialty in soccer participated in the study. They performed exercises involving isometric, concentric, and eccentric muscle contractions. The electromyographic recordings were amplified by a factor of 1000, rectified, and integrated. Mean integrated values were calculated by dividing the elapsed time for the five repetitions, to provide the mean integrated electromyographic values for each exercise. Leg movements from a long lying position showed higher activity of the rectus abdominis, compared to the EO (p < 0.001). The dynamic sit-ups showed an obvious dominant activity of the EO, compared to the rectus abdominis (p < 0.001). During eccentric exercise, higher activity was found in the RAU, compared to the RAL (p < 0.001). The results could serve as a basis for improving the design and specification of training exercises. Pre-exercises should be performed before testing abdominal muscle strength.

The effects of free weights and isoinertial resistance during semisquatting exercise on amateur soccer players' physical performance indicators: a randomized controlled study.

BACKGROUND: The aim of this study was to compare the effects of two lower extremity strengthening programs using isoinertial resistance or free weights on amateur soccer players' physical performance indicators. METHODS: Thirty-five amateur soccer players (average age 22.6±5.1 years) were randomly assigned to isoinertial group (N.=11) or free-weight group (N.=11), or control group (N.=13). The groups performed two training sessions per week for six weeks. Before and after the strengthening implementation, physical performance indicators were evaluated, including the isokinetic knee extensors and flexors' strength, power, speed, and agility. The significance level was set at P<0.05. RESULTS: The isoinertial training resistance led to an increase in the hamstrings' eccentric strength at 60°/s and 150°/s (P<0.05) compared to the free-weight resistance (P>0.05) and the controls (P>0.05). No other significant adaptations were observed in the other isokinetic strength, power, speed (10-m, P=0.052) and agility measurements (Illinois Agility Test, P=0.059). In ratio (knee flexors/knee extensors) the only differences observed were at 150°/s for isoinertial group (P<0.05). CONCLUSIONS: Isoinertial resistance training during semisquatting can enhance the hamstrings' eccentric performance and the soccer players' speed and agility compared to the classic free-weight training program, which should consider when designing strength and injury prevention programs.

The significant role of scoring from set plays in the 2018 FIFA World Cup.

BACKROUND: The aim of this study was to analyze the set-play goals achieved and VAR influence in the 2018 World Cup as well as to examine their impact on game outcome. METHODS: We analyzed 71 goals that have been scored from a set-play during the 2018 World Cup. We did not include the goals achieved during penalty process. χ2 analysis was used, and the level of significance was set at P<0.05. RESULTS: Overall, 42% of all goals came from set-plays in 64 matches of this tournament, which is on average 1.1 per match. The team that scored one or more goals via set-plays, won 71.1% of the occasions (χ2=24.368, P<0.001). Results showed that 22 goals achieved from corner kicks, and the most effective delivery area was the goal center area. Most of the goals (75.0%) from indirect free kick came from the sides, which had significant difference with the central area (χ2=4.000, P<0.05). All the goals (6) from direct free kick, were scored from the central area out of the 16.5-m box and the distance was <25 m from the goal in all of them. In total, 17 referee decisions changed after VAR reviews and 9 resulted in goals and 89% of them impact the current game outcome. CONCLUSIONS: The findings of this study highlighted the importance of scoring from set plays to game outcome. Coaches should be aware of the above findings in to order to make their teams more effective both in terms of attacking and defending a set-play situation.

Match Running Performance of Elite Soccer Players: V̇o2max and Players Position Influences.

ABSTRACT: Metaxas, TI. Match running performance of elite soccer players: V̇o2max and players position influences. J Strength Cond Res 35(1): 162-168, 2021-The aims of this study were (a) to assess the relationship between laboratory-measured V̇o2max with total distance covered in a soccer match, (b) to assess the relationship between laboratory-measured V̇o2max with the distance covered at a different running intensity in a soccer match, (c) to quantify different intensity running in various playing positions, and (d) to determine the differences of running performance between halves. Analyzed match running performance of the Greek elite (n = 14) soccer players using a global positioning system within the second division professional league. No correlation was found between V̇o2max and match running performance at any velocity. The players covered greater distances in the first half at all speed levels except walking. In the first half, they covered a greater distance than in the second half (1,533 vs. 1,297 m, p < 0.001; 879 vs. 708 m, p < 0.001; 433 vs. 359 m, p < 001; 185 vs. 152 m, p < 0.01; 81.4 vs. 65.5 m, p < 0.001) when jogging, running, high-intensity running, fast running, sprint and total, respectively. Wide players covered greater distances at fast running (p < 0.001) and sprint zone than the players who played at the axon of the field (348 vs. 297 and 186 vs. 113 m, respectively). In addition, midfielders covered a greater distance at high-intensity running zone and at fast running zone than the defenders and forwards (1,768 vs. 1,372 m, p < 0.01 and 1,768 vs. 1,361 m, p < 0.01; 686 vs. 878 m, p < 0.01 and 709 vs. 878 m, p < 0.05, respectively). The results demonstrate that match running performance and the distance covered depends on the tactical role of each player in the team. These data provide valuable information for coaches regarding the running profile of the Greek elite soccer players that could be used to design a more effective training program.

The effects of an integrative training program on elite young soccer players' physical performance.

BACKGROUND: The aim of this study was to investigate the effects of a short duration and low weekly frequency integrative program on sprint, agility and jump performance in elite youth soccer players. METHODS: Twenty-eight elite youth soccer players, members of two professional clubs, playing in the U19 developmental championship participated in this study. They were divided into 2 groups: the intervention group (EG, N.=15) and the control group (CG, N.=13). The duration of the intervention program was 8 weeks with a frequency of twice per week. The performance of the participants in the 10 meters and 30 meters speed, countermovement jump (CMJ), squat jump (SJ) and agility (Illinois agility test, Arrowhead agility test) was measured at the beginning and the end of the 8-week study. RESULTS: There was no statistically significant difference in any performance measured between the two groups. CONCLUSIONS: The results of the present study indicate that the addition of allowing frequency and short duration training intervention program did not enhance the physical fitness indicators, in high-level young soccer players.

The effects of soccer training in aerobic capacity between trained and untrained adolescent boys of the same biological age.

BACKROUND: The purpose of this study was to examine the effects of soccer training on maximal oxygen uptake and anthropometric characteristics in different ages of soccer players and untrained adolescents of the same biological age. METHODS: A total of one hundred and twenty-six (N.=126) young soccer players and untrained boys throughout the developmental ages of 12 (soccer players N.=22; untrained boys = 22) 14 (soccer players N.=20; untrained boys = 18) and 16 (soccer players N.=22; untrained boys = 22) volunteered to participate in the study. Sexual maturation was classified according to Tanner's stages. Soccer players participated both in their school's physical education program and in a soccer training program, while the untrained participated only in their school's physical education program. All participants underwent anthropometric measurements and performed a maximal exercise test on a motor driven treadmill to determine maximal oxygen uptake (V̇O2max) and cardiorespiratory indices. Blood lactate (BL) concentration was determined in the 5th minute of recovery using a lactate photometer. RESULTS: The trained group showed significantly higher V̇O2max, in absolute and relative values (P<0.001), BLmax (P<0.05) and maximal respiratory exchange ratio (RERmax) (P<0.05) compared to the untrained group. Resting heart rate (HR) and systolic blood pressure were significantly lower (P<0.05) for the trained compared to untrained. CONCLUSIONS: The results of this study showed that systematic soccer training has a positive effect in the central cardiovascular system expressed as V̇O2max, HR and blood pressure.

Effects of soccer training in muscular strength: a comparative study in trained youth soccer players and untrained boys of the same biological age.

BACKGROUND: It is not clear if soccer training affected the development of muscle strength positively in children. We hypothesize that soccer training could positively affect the isokinetic concentric muscle strength and anthropometric characteristics in different ages of adolescents of the same biological age. METHODS: A total of 126 young soccer players (N.=66) and untrained boys (N.=60) throughout the developmental ages of 12, 14 and 16 years volunteered to participate in the study. Sexual maturation was classified according to Tanner's stages. Soccer players, except from their school's physical education program, participate also in a soccer training program. All participants underwent anthropometric measurements. The isokinetic-concentric peak torque values of the hamstrings (H) and quadriceps (Q), as well as the conventional strength ratios of H:Q, were measured on an isokinetic dynamometer at angular velocities of 60, 180, and 300°·s-1. RESULTS: Anthropometric differences in the same age group, between trained and untrained, were presented only for 12-year-olds (height, P<0.001 and BMI, P<0.01). Between groups, differences were observed in almost all anthropometric measurements, probably as result of development. The absolute isokinetic-concentric muscle strength was significantly higher (P<0.001) in the 12- and 16-year-old trained group, compared to untrained, for the knee-flexors and knee-extensors. However, no significant differences were found between the trained and untrained 14-year-olds, for the muscle groups of Q and H. The H:Q strength ratios did not differ between groups at all angular velocities. CONCLUSIONS: The results of this study showed that systematic soccer training has a positive effect in the peripheral system, expressed as an increased lower limb muscle strength; specifically, Q and H.

Myosin heavy chain isoform composition in the deltoid and vastus lateralis muscles of elite handball players.

The purpose of the present study was to compare the myosin heavy chain (MHC) isoform composition of the deltoid and vastus lateralis muscles of the dominant and non-dominant limbs in handball players. Eleven male Greek elite handball players (age 22.6 ± 1.9 yrs, training experience 10.6 ± 2.1 yrs, height 184.1 ± 4.1 cm, and weight 81.0 ± 12.5 kg) participated in the study. Four muscle biopsies were obtained from the dominant and non-dominant deltoid and vastus lateralis muscles during the in-season period. The MHC composition was determined using SDS-PAGE. No significant difference was found between the dominant and non-dominant muscles; Deltoid muscle: MHC I [(95%CI = -1.22, 0.33), P = 0.228], MHC ΙΙa [(95%CI = -0.32, 1.59), P = 0.168] and MHC IIx [(95%CI = -1.49, 1.10), P = 0.749]; Vastus lateralis muscle: MHC I [(95%CI = -0.38, 0.63), P = 0.586], MHC ΙΙa [(95%CI = -0.50, 0.65), P = 0.783] and MHC IIx [(95%CI = -1.08, 0.42), P = 0.355]. The findings of the present study indicate that the greater use of the dominant limbs for throwing actions and body movements in handball do not lead to altered MHC isoform composition compared to the non-dominant limbs.

Muscle-tendon morphology and function following long-term exposure to repeated and strenuous mechanical loading.

We mapped structural and functional characteristics of muscle-tendon units in a population exposed to very long-term routine overloading. Twenty-eight military academy cadets (age = 21.00 ± 1.1 years; height = 176.1 ± 4.8 cm; mass = 73.8 ± 7.0 kg) exposed for over 24 months to repetitive overloading were profiled via ultrasonography with a senior subgroup of them (n = 11; age = 21.4 ± 1.0 years; height = 176.5 ± 4.8 cm; mass = 71.4 ± 6.6 kg) also tested while walking and marching on a treadmill. A group of eleven ethnicity- and age-matched civilians (age = 21.6 ± 0.7 years; height = 176.8 ± 4.3 cm; mass = 74.6 ± 5.6 kg) was also profiled and tested. Cadets and civilians exhibited similar morphology (muscle and tendon thickness and cross-sectional area, pennation angle, fascicle length) in 26 out of 29 sites including the Achilles tendon. However, patellar tendon thickness along the entire tendon was greater (P < .05) by a mean of 16% for the senior cadets compared with civilians. Dynamically, cadets showed significantly smaller ranges of fascicle length change and lower shortening velocity in medial gastrocnemius during walking (44.0% and 47.6%, P < .05-.01) and marching (27.5% and 34.3%, P < .05-.01) than civilians. Furthermore, cadets showed lower normalized soleus electrical activity during walking (22.7%, P < .05) and marching (27.0%, P < .05). Therefore, 24-36 months of continuous overloading, primarily occurring under aerobic conditions, leads to more efficient neural and mechanical behavior in the triceps surae complex, without any major macroscopic alterations in key anatomical structures.

Maximal oxygen consumption and oxygen muscle saturation recovery following repeated anaerobic sprint test in youth soccer players.

BACKGROUND: The purpose of the study was to examine whether differences in aerobic capacity (VO2max) influence muscle reoxygenation following repeated anaerobic sprint test (RAST) in soccer players. We hypothesized that muscle reoxygenation is faster in players with higher aerobic capacity. METHODS: Ten male, youth soccer players participated in the study and performed RAST on a synthetic grass field. Oxygen saturation in muscle (StO2) of the right vastus lateralis muscle was measured by near-infrared spectroscopy. Half the time that was required for StO2 recovery (T1/2 StO2) after RAST was used to evaluate the reoxygenation in the recovery period after testing. The T1/2 StO2 was defined as the time from the end of RAST testing to the time of reaching 50% of StO2. Aerobic capacity (VO2max) was estimated by the Yo-Yo Intermittent Recovery Test level 1 (YYIR1). RESULTS: The T1/2 StO2 had a significant inverse correlation with VO2max (r=-0.71; P=0.021) and with the distance which was covered by players on YYIR1 test (r=-0.71; P=0.021). In contrast, StO2 recovery rate showed no significant correlations with the VO2max in subjects. CONCLUSIONS: These results indicate that aerobic capacity can influence vastus lateralis reoxygenation following RAST in youth soccer players.

Correlation of Fiber-Type Composition and Sprint Performance in Youth Soccer Players.

Metaxas, T, Mandroukas, A, Michailidis, Y, Koutlianos, N, Christoulas, K, and Ekblom, B. Correlation of fiber-type composition and sprint performance in youth soccer players. J Strength Cond Res 33(10): 2629-2634, 2019-The aim of this study was to examine the correlation between muscle fiber type and sprint performance in elite young soccer players of different age groups of the same team. Twenty-eight young players participated in this study (group U15, n = 8; group U13, n = 9; and group U11, n = 11). Anthropometric assessments, acceleration (10 m), and Bangsbo modified sprint test (30 m) were performed. Muscle biopsies were obtained from the vastus lateralis, and after that, fiber-type composition was determined by immunohistochemistry. No significant correlations were found between the sprint test and muscle fiber distribution for the groups U13 and U11 (p > 0.05). Also, no correlations were found between cross-sectional areas in the types of fibers with the sprint test in all groups (p > 0.05). A positive correlation was found between type I fibers and the performance in the acceleration test (10 m) (r = 0.77, p < 0.05) was found only in group U15 and a negative correlation between type IIA fibers and the performance in the acceleration test (10 m) (r = -0.89, p < 0.05). The correlations were observed only in group U15, which may indicate that the duration and the intensity of the soccer systematic training can affect the plasticity of the muscle fibers. Specific soccer training in youth is one of the factors that can affect fiber-type plasticity. The specific training programs and status of U15 are more intensive, and the exercises are oriented more to improve physical fitness.

Variation of aerobic performance indices of professional elite soccer players during the annual macrocycle.

BACKGROUND: The purpose of the present study was to examine the variation of aerobic performance parameters of elite Greek soccer players. METHODS: In the study participated twenty-four (24) male professional soccer players (age: 24.3±4.3 years, height: 180.3±3.8 cm and mass: 77.4±6.1 kg), who competed at the top level of the Greek National Championship. Four measurements regarding aerobic parameters were conducted during the annual training cycle (preseason, start of the season, end of the first championship round and end of the season). RESULTS: The ANOVA analysis showed that maximum oxygen uptake (VO2max) was significantly increased after the completion of the preseason and continued to increase until the end of the first round of the Championship. In contrast, a decline was observed towards the end of the season. The velocity to maximum oxygen uptake (vVO2max) and the velocity parameter in respiratory threshold were significantly increased at the end of the preseason and the end of the first round, while the parameters were differentiated at the end of the season. The lactate concentration showed no significant changes during the four measurements. CONCLUSIONS: A systematic observation of players' performance, especially recording parameters such as VO2max, during the annual training cycle, could provide the necessary feedback for both trainers and players in order to increase team performance.