Different Sampling Frequencies to Calculate Collective Tactical Variables during Competition: A Case of an Official Female's Soccer Match.

The objective of the study was to assess the impact of the sampling frequency on the outcomes of collective tactical variables during an official women's soccer match. To do this, the first half (lasting 46 min) of an official league match of a semi-professional soccer team belonging to the Women's Second Division of Spain (Reto Iberdrola) was analysed. The collective variables recorded were classified into three main groups: point-related variable (i.e., change in geometrical centre position (cGCp)), distance-related variables (i.e., width, length, height, distance from the goalkeeper to the near defender and mean distance between players), and area-related variables (i.e., surface area). Each variable was measured using eight different sampling frequencies: data every 100 (10 Hz), 200 (5 Hz), 250 (4 Hz), 400 (2.5 Hz), 500 (2 Hz), 1000 (1 Hz), 2000 (0.5 Hz), and 4000 ms (0.25 Hz). With the exception of cGCp, the outcomes of the collective tactical variables did not vary depending on the sampling frequency used (p > 0.05; Effect Size < 0.001). The results suggest that a sampling frequency of 0.5 Hz would be sufficient to measure the collective tactical variables that assess distance and area during an official soccer match.

Reference values for collective tactical behaviours based on positional data in professional football matches: a systematic review.

Match collective tactical behaviours can be used as a reference to design and select training strategies to improve individual and team performance in professional football. The aim of the systematic review was to cluster the collective tactical variables used to highlight and compare male soccer teams' collective behaviour during professional official matches, providing reference values for each of them. A systematic review of relevant articles was carried out using three electronic databases (PubMed, SPORTdiscus and Web of Science). From a total of 1,187 studies initially found, 13 original articles were included in the qualitative synthesis. The articles found concerned studies carried out on the Spanish, Portuguese, English and Brazilian 1st divisions and during the European UEFA Champions League. The team length and width ranged from 31 to 46 m and from 35 to 48 m, respectively. The distance from a defending team's goalkeeper to the nearest teammate ranged from 9 ± 6 to 30 ± 7 m, the goal line-recovery location from 27 to 37 m, and the opponent's goal line from 42 to 50 m. The stretch index ranged from 7 to 16 m. Mean team area was ~900 m2 and the area of the pitch which included all outfield players divided by the 20 outfield players ranged from 79 ± 15 to 94 ± 16 m2. All studies provided greater distance and area values during the team-possession phase in comparison to the non-possession one. The ball location on the pitch determined the collective tactical behaviour of the teams. The differences between halves in the distance and area values were contradictory. Further studies should assess the effect of the interaction between the contextual factors on the collective tactical behaviour to obtain more accurate references. This could help football coaches in the design of suitable training tasks to optimize tactical performance.

Tell me how and where you play football and I'll tell you how much you have to run.

The aim of this study was to describe the team accumulated physical response per minute considering only the effective playing time (EPT) attending to different contextual and strategic variables in the Spanish Football First Division (LaLiga Santander). A sample of 2,959 performances was included in the analysis, considering a 4-year period of analysis (from 2016-17 to 2019-20). The physical variables were: total distance covered with (DTminPOS) and without (DTminNOpos) possession of the ball, and distance covered at > 21 km·h-1 with possession (DT21minPOS) and without (DT21minNOpos). Two contextual variables, i.e. Place (Home/Away) and Score (Lost/Draw/Win), and two strategic variables, i.e. level of effective playing time (LevelETP) and level of possession of the ball (LevelPOS), were analysed. The teams ran more without possession of the ball than with possession; nevertheless, the teams that had less possession of the ball had higher values in the distance covered at > 21 km·h-1 with possession of the ball and vice versa. Furthermore, the strategic variables also had influence on the physical response (DT and DT21) of the teams,LevelETP and LevelPOS, although with interactive effects: longer playing time, less accumulated distance, and greater possession, greater accumulated distance in the defensive phase, both per min. The findings of this study may offer important practical implications to practitioners in order to assess physical performances of the players in matches, because it is crucial to integrate in the analysis the different contextual and strategic variables where the match has taken place to assess performances of the teams.

Variability of professional soccer players' perceived match load after successive matches.

This study analyses the differential perceived match load accumulated by professional soccer players depending on their: (a) participation in several consecutive official matches within the same week (Pre_Cup, Cup, and Post_Cup), and (b) total match participation time (i.e. 90 min, 70-90 min and < 70 min). Participants were 21 Spanish Second Division professional soccer players (M age = 27.1, SD = 3.3 years; M body height = 182.1, SD = 3.9 cm; M body mass = 75.8, SD = 5.14 kg). There were no significant differences (p > 0.05) in dRPE-ML among Pre_Cup, Cup and Post_Cup matches or in dRPE-ML between teams that took part in two or three official matches within the same week or three official matches in 2-4 consecutive weeks. The results suggest that participating in several matches in the same week does not increase accumulated perceived exertion for professional soccer players.

A Survey to Assess the Quality of the Data Obtained by Radio-Frequency Technologies and Microelectromechanical Systems to Measure External Workload and Collective Behavior Variables in Team Sports.

Electronic performance and tracking systems (EPTS) and microelectromechanical systems (MEMS) allow the measurement of training load (TL) and collective behavior in team sports so that match performance can be optimized. Despite the frequent use of radio-frequency (RF) technology (i.e., global positioning navigation systems (GNSS/global positioning systems (GPS)) and, local position systems (LPS)) and MEMS in sports research, there is no protocol that must be followed, nor are there any set guidelines for evaluating the quality of the data collection process in studies. Thus, this study aims to suggest a survey based on previously used protocols to evaluate the quality of data recorded by RF technology and MEMS in team sports. A quality check sheet was proposed considering 13 general criteria items. Four additional items for GNSS/GPS, eight additional items for LPS, and five items for MEMS were suggested. This information for evaluating the quality of the data collection process should be reported in the methods sections of future studies.

Quantification of the Perceived Training Load in Young Female Basketball Players.

Otaegi, A and Los Arcos, A. Quantification of the perceived training load in young female basketball players. J Strength Cond Res 34(2): 559-565, 2020-The purposes of this study were (a) to compare training session, match, and weekly perceived training load (TL) between U15 and U16 female basketball players and (b) within the teams, to assess the relationship between perceived TL and the changes in physical fitness performance during an in-season 9-week period. Twenty-one female players from U15 and U16 female teams from the same Spanish club participated in the study. Before and after the study, players were tested to determine physical fitness performance (using Yo-Yo IR1, countermovement jump, T-Test, and 15 m sprint). Each player declared her perceived exertion (PE) for the whole training session and match using Foster's 0-10 scale. Training week perceived TL was higher for the U16 players than the U15 players; U16 players considered the training and matches to be more difficult. In both teams, the perceived TL of the last training session of the week was significantly lower (Effect sizes = large-very large) than the other sessions. Although substantial negative associations (r = 0.52-0.78) were detected between the changes in physical fitness performance and the accumulated volume, sum of PEs and perceived TL in the U15 players, these associations were unclear in the U16 players. The basketball coaches-periodized training goals are to attain the highest session perceived TLs in the middle of the week and to reduce it considerably in the last training session. The U16 and U15 players accumulated perceived TL in different ways. Although the practice volume was similar in both teams, the older players consider the sessions more difficult. The relationship between the perceived TL and the changes in physical fitness performance varied between teams. Based on our findings, we propose that the PE-based dose-response model should be applied with caution in young female basketball players.

Are acceleration and cardiovascular capacities related to perceived load in professional soccer players?

This study aims at assessing physical fitness performance and its relationship with the differential ratings of perceived exertion of training load (dRPE TL) and match load (dRPE ML) in a Spanish professional soccer team at the beginning of several in-season periods: 1-4 weeks, 5-8 weeks and 1-8 weeks. Performance and mechanical variables over the acceleration phase, as well as cardiovascular performance variables were evaluated in 20 male professional soccer players of a team competing in the Spanish Second Division League. Moreover, dRPE TL and dRPE ML were quantified. The dRPE TL showed negative and large associations between both maximal aerobic speed (MAS) and maximal oxygen consumption (VO2max) (from r = -0.53; ± 0.06 to r = -0.53; ± 0.05 95% CL, p = 0.035 to 0.036) and RPEres TL values throughout the 5-8 and 1-8 week periods. Furthermore, dRPE ML positive and large associations were found between players initial MAS or VO2max (from r = 0.50; ± 0.17 to r = 0.56; ± 0.11 95% CL, p = 0.026 to 0.049) and RPEmus ML in 1-4 and 1-8 week periods. The current study suggests that a better cardiovascular capacity could be connected with a lower RPEres TL and higher RPEmus ML.

The use of technology and sampling frequency to measure variables of tactical positioning in team sports: a systematic review.

The aim of the study was to assess the use of different positioning systems and sampling frequencies to measure spatial-positioning variables in team sports. Articles were selected when the sampling frequency was detailed. 2,194 articles were identified and 59 works were selected for the systematic review. The sampling frequency used to measure tactical behaviour differed considerably among studies. For Global Navigation Satellite System, the sampling frequency ranged from 5- to 15 Hz for raw data, the most commonly used sampling frequency being 5 Hz. For Optic-based tracking systems, the sampling frequency ranged from 10- to 30 Hz. For Local Position System, the sampling frequency ranged from 45- to 100 Hz, the most commonly used sampling frequency being 42 Hz and 57.7 Hz. There is no common criterion in the sampling frequency used to measure each tactical variable. Further studies should investigate the impact of the sampling frequency on the measurement of the tactical variables.

Physical Fitness Performance of Young Professional Soccer Players Does Not Change During Several Training Seasons in a Spanish Elite Reserve Team: Club Study, 1996-2013.

Los Arcos, A and Martins, J. Physical fitness performance of young professional soccer players does not change during several training seasons in a Spanish elite reserve team: club study, 1996-2013. J Strength Cond Res 32(9): 2577-2583, 2018-The purpose of this study was to assess the changes in physical fitness performance in young professional soccer players during several training seasons in a Spanish elite reserve team. Physical test values (i.e., vertical jump test, straight line sprint test, and discontinuous and progressive submaximal running test) of 97 young professional soccer players who belonged for at least 2 consecutive seasons to the reserve team of a Spanish professional team from 1996 to 2013 were analyzed. A distinction was made between the soccer players who were promoted to the Spanish first/second divisions (n = 38) and those who were not (n = 59) (until the end of the 2016/2017 season). Players were also classified according to their playing positions. Independently of the competitive level reached and the playing position, the variability of the fitness performance was limited (coefficient of variation <6%) and the players did not improve their fitness values (effect size ≤ small) from the first to the last season in which they were enrolled in the team (after 2-4 seasons). During the last stage of training in an elite soccer academy, young professional soccer players achieve a very similar physical fitness performance when their soccer competence is evaluated, and other soccer performance factors are those which make them stand out for selection.

Objective and subjective methods for quantifying training load in wheelchair basketball small-sided games.

The aim of the present study was to analyse the training load in wheelchair basketball small-sided games and determine the relationship between heart rate (HR)-based training load and perceived exertion (RPE)-based training load methods among small-sided games bouts. HR-based measurements of training load included Edwards' training load and Stagno's training impulses (TRIMPMOD) while RPE-based training load measurements included cardiopulmonary (session RPEres) and muscular (session RPEmus) values. Data were collected from 12 wheelchair basketball players during five consecutive weeks. The total load for the small-sided games sessions was 67.5 ± 6.7 and 55.3 ± 12.5 AU in HR-based training load (Edwards' training load and TRIMPMOD), while the RPE-based training loads were 99.3 ± 26.9 (session RPEres) and 100.8 ± 31.2 AU (session RPEmus). Bout-to-bout analysis identified greater session RPEmus in the third [P < 0.05; effect size (ES) = 0.66, moderate] and fourth bouts (P < 0.05; ES = 0.64, moderate) than in the first bout, but other measures did not differ. Mean correlations indicated a trivial and small relationship among HR-based and RPE-based training loads. It is suggested that HR-based and RPE-based training loads provide different information, but these two methods could be complementary because one method could help us to understand the limitations of the other.

Sprint and jump performances do not determine the promotion to professional elite soccer in Spain, 1994-2012.

The aims of this study are (a) to describe the evolution of neuromuscular performance over an 18 year period within a Spanish elite reserve team; (b) to check if there were any relation between the playing position and sprint and jump performances and (c) to look into the alleged impact of this factor on the top playing level attained by the soccer players. We considered the physical tests (5 m and 15 m sprint times and countermovement jump (CMJ) height) made by 235 players enrolled in the reserve team of the Club from 1994 to 2012 and the highest competitive-level they achieved: Spanish first (n = 39) and second divisions (n = 36) and semi-professional (n = 160). Furthermore, the players were classified according to their playing positions. The main findings were a very-likely/most-likely lower neuromuscular performance (ES = 0.48-0.68, small to moderate) in the last six-season term (2006-2012) than in the first term (1994-2000); possibly/very-likely lower performances in sprinting and CMJ (ES = 0.22-0.55, small) by central defenders (CDs) and midfielders than by other playing positions; very-likely better performances in sprinting and jumping by first and second divisions central defenders than by semi-professional central defenders (ES = 0.90-1.02, moderate). Sprint and jump performances are not a relevant physical parameter to promote to the top level of soccer in Spain except for one in six of the playing positions: CDs.

Effects of horizontal plyometric training volume on soccer players' performance.

The aim of this study was to examine the dose response effect of strength and conditioning programmes, involving horizontally oriented plyometric exercises, on relevant soccer performance variables. Sixteen soccer players were randomly allocated to two 6-week plyometric training groups (G1 and G2) differing by imposed (twice a week) training volume. Post-training G1 (4.13%; d = 0.43) and G2 (2.45%; d = 0.53) moderately improved their horizontal countermovement jump performance. Significant between-group differences (p < 0.01) in the vertical countermovement jump for force production time (T2) were detected post-training. No significant and practical (p > 0.05, d = trivial or small) post-training improvements in sprint, change of direction ability (CODA) and horizontal arm swing countermovement jump were reported in either group. Horizontal plyometric training was effective in promoting improvement in injury prevention variables. Doubling the volume of a horizontal plyometric training protocol was shown to have no additional effect over functional aspects of soccer players' performance.

Quantification of the perceived training load and its relationship with changes in physical fitness performance in junior soccer players.

The aim of this study was to determine the relationship between perceived respiratory and muscular training load (TL) and changes in physical fitness in elite and non-elite junior soccer players. Twenty-eight elite (n = 14, 17.6 ± 0.6 years, 70.3 ± 4.4 kg, 179.7 ± 5.6 cm) and non-elite (n = 14, 17.5 ± 0.5 years, 71.1 ± 6.5 kg, 178.1 ± 5.6 cm) soccer players belonging to a Spanish first and third division football academies and competing in junior Spanish first division (2012-2013) participated in the study. Countermovement jump (CMJ), CMJ arm swing, 5 and 15 m sprints and the Université de Montreal endurance test were performed in January and 9 weeks later in March. In order to quantify TLs, after each training session and match, players reported their session rating of perceived exertion (sRPE) separately for respiratory (sRPEres) and leg musculature (sRPEmus). Elite players accumulated greater weekly training volume (361 ± 14 vs. 280 ± 48 min; effect sizes (ES) = 5.23 ± 1.74; most likely), and perceived respiratory (1460 ± 184 vs. 1223 ± 260 AU; ES = 1.12 ± 0.79; very likely) and muscular (1548 ± 216 vs. 1318 ± 308 AU; ES = 0.99 ± 0.84; likely) TL than did non-elite players. Training volume, sRPEres-TL and sRPEmus-TL were positively and largely correlated (r = 0.67-0.71) with the changes in aerobic fitness. The present results suggest that a low training volume and TL can impair improvement in aerobic fitness in junior soccer players during the in-season period.

Variability of objective and subjective intensities during ball drills in youth soccer players.

The aim of this study was to examine the intrasubject (intraclass coefficient correlation [ICC]) and intersubject variability (coefficient of variation [CV]) of soccer ball drills (BD) involving or not opposition in male youth soccer. For this purpose, a collective ball dribbling (DB) exercise and a 7-a-side ball game without coach encouragements were considered. Exercise intensity was assessed as heart rate (HR), training load (TL), and perceived exertion scales. Fourteen U-14 male soccer players (age, 14.79 ± 0.43 years and experience, 6.5 years) of a Spanish First Division club academy participated in the study. Ball drills were examined for variability over 5 successive training sessions in similar field conditions. Results showed that 7-a-side was significantly (p = 0.000) more demanding than DB. Indeed the TL, HRmax, HRmean, overall perceived exertion, and leg muscular perceived exertion (MPE) resulted 141, 8.7, 11, 56, and 72%, higher in 7-a-side than in DB, respectively. In the 7-a-side condition, good intersubject (CV < 10%) and low intrasubject (ICC < 0.7) variability were observed. In the DB condition, CVs were below 10% CV only for HR variables and the ICC values were higher than 0.7 only for MPE. Despite the moderate reproducibility of BD not considering opponents, this condition did not reveal to induce homogeneous physiological responses in young soccer players. Therefore, the use of this kind of drills may be questionable when considered as alternative of moderate intensity generic aerobic training. Despite the higher interaction between players variability in the opposition drills resulted lower, this suggests their use as a specific conditioning exercise.

Correlation between agility and sprinting according to student age.

The purposes of the study were to assess sprinting and agility performance characteristics and to determine the relationship between these two motor skills in elementary education students. Sprinting and agility performance were assessed in 176 children (88 boys and 88 girls) divided into three groups: Group 1 (G1, N = 98; 48 boys and 50 girls), from the first year of elementary education; Group 2 (G2, N = 38; 15 boys and 23 girls), from the second year of elementary education; Group 3 (G3, N = 40; 25 boys and 15 girls), from the third year of elementary education. Significant differences (p < 0.001) were found in agility ability among the groups and between G1-G3 and G2-G3 in the 5 and 15 m sprint. Regarding gender of the students of the same age, significant differences (p < 0.001) between boys and girls in group G1 and G2 were obtained in the 5 and 15 m sprint. The correlation between agility and acceleration was significant but moderate (0.3 < r < 0.7) in all groups (G1, G2, and G3), in most cases. When the gender factor was included, the results were heterogeneous. Assessing this correlation according to age and gender produced heterogeneous results. For this reason, we think that both are independent qualities and that age and gender are two factors that influence the correlation results.

Nonuniform changes in MRI measurements of the thigh muscles after two hamstring strengthening exercises.

Although many different hamstring strengthening exercises exist, the effect on site specific activation of these exercises on different muscles of the leg is unclear. This study investigated the effects of the eccentric leg curl (LC) and lunge (L) exercises on the biceps femoris long head (BFl), biceps femoris short head (BFs), semitendinosus (ST), semimembranosus (SM), and adductor magnus (AM). Each leg of 11 male professional soccer players was randomly assigned to an LC or L exercise protocol (3 sets of 6 repetitions). Functional magnetic resonance imaging (fMRI) of the subjects' thighs were performed before and 48 hours after the intervention. Fifteen axial scans of the thigh interspaced by a distance of 1/15 right femur length (Lf) were obtained. The fMRI data were analyzed for signal intensity changes. No significant changes were observed in absolute short tau inversion recovery values for the SM and BFs. Significant changes for the ST (∼21-45%) from sections 4 to 10, AM (∼2-13%) at section 4, and BFl (∼ -3 vs. 8%) at section 7 were noted. LC exercises load all the regions of the ST muscle. The L exercises load the proximal regions of the BFl and AM. These findings may have relevance when designing protocols for prevention and rehabilitation of hamstring injuries.

Effects of different contextual interference training programs on straight sprinting and agility performance of primary school students.

The aim of this study was to evaluate the effect of a different degree of contextual interference (CI) training program on the change of direction ability (CODA) itself and on the straight sprinting (SSP) performance (5 m and 15 m) in students in the first year of primary school. It also evaluated which CI training program was more effective. Eighty eight students (6.42 ± 0.38 yr) volunteered as participants for the present study. Participants were randomized into 5 different CI training programs (LCI: low contextual interference, MCI: moderate contextual interference, HCI: high contextual interference, VCI: variable contextual interference, and CG: control group) during a 3 week period. Significant CODA improvements (p < 0.05) in pre-post-test were found in MCI (4.39%, ES 0.41) and VCI (9.37%, ES 1. 12) groups. Furthermore, LCI, MCI and HCI groups ameliorated their SSP performance, both in 5 m (5. 92%, ES 0.81; 6.67%, ES 0.90; 8.05%, ES 1.33 respectively) and 15 m SSP (5.86%, ES 0.76; 6.47%, ES 0.80; 2.47% ES 0.41 respectively). These results suggest that training through games of tag (VCI) was the most effective in improving the CODA and training with moderate contextual interference (MCI) was the only type which induced improvements in both capacities (SSP and CODA). Key PointsWe investigated the CODA and SSP performance of students in the first year of primary school and the influence of 5 different training programs on their CODA and SSP ability.Training through games of tag (VCI) was the most effective in improving the CODATraining with moderate contextual interference (MCI) was the only one which induced improvements in both capacities (SSP and CODA).

Tactical Analysis According to Age-level Groups during a 4 vs. 4 Plus Goalkeepers Small-sided Game.

This study aimed to compare the collective dynamics of three different age-level groups (i.e., U13, U15 and U18) during a 4 vs. 4 plus goalkeepers small-sided game (SSG). Fifty-four male outfield soccer players aged between 13 and 18 years took part in the study. Team tactical behaviors were assessed by measuring (a) the area occupied by players of each team, (b) the distance between both teams' centroids, (c) the players' distance to their own team and d) the stretch index during a 4 vs. 4 plus goalkeepers SSG format. The main results revealed that larger areas were occupied by the older players (P < 0.001; Effect size (ES) = 0.44-0.25, small). Additionally, the mean distance between teams' centroids was greater in older groups (P < 0.001; ES = 0.44-0.81, large-small). Finally, the distance between players (P < 0.001; ES = 0.75-0.81, moderate-large) and the stretch index (P < 0.001; ES = 0.44-0.47, small) were also greater in older age categories. The evidence provided in the present study might help coaches identify the influence of age on collective dynamics during SSGs and help them find task conditions that could help to improve the behaviors and positioning of younger players.

Assessing the Perceived Exertion in Elite Soccer Players during Official Matches According to Situational Factors.

This study aimed to assess the match perceived exertion (PE) declared by starter and non-starter junior elite soccer players, according to the level of the opponents, and by playing at home or away. Nineteen young soccer players who competed in the Spanish U19 League participated in this study. PE was registered during the entire regular season (30 official matches). Players were grouped by match playing time: starters (players who started the game and played at least 45 min) and non-starters (substitute players who participated for less than 45 min). Moreover, the matches were classified according to the opponent level (i.e., high, medium, or low) and the match location (i.e., home or away). Starters who competed against high-level opponents (8.7 ± 0.6) declared higher PE ratings than against medium (8.1 ± 0.7, p < 0.01) and low (8.4 ± 0.7, p < 0.01) level opponents. In addition, starters competing at home declared lower PE ratings than when playing away (8.2 ± 0.8 vs. 8.5 ± 0.6, p < 0.01). However, no significant differences (p > 0.05) were observed for non-starters. Coaches should consider not only tactical-strategic needs, but also these contextual factors when managing the match playing time of the starter players.

Assessing the Anthropometric Profile of Spanish Elite Reserve Soccer Players by Playing Position over a Decade.

The aims of this study were to describe the evolution of the anthropometric profile of soccer players over a decade and to compare the anthropometric profiles of players promoted from an elite reserve team to high-level soccer with those players who were not promoted. We examined the body mass, height, body-mass index, and body fat of 98 players enrolled in the reserve team from 2008 to 2018. The players were classified in terms of (a) the highest competitive level they achieved up to the 2019/2020 season (i.e., Spanish 1st-2nd divisions or semi-professional); (b) the period in which they played their last season on the team; and (c) their playing position. Over time, the height of goalkeepers, lateral midfielders, and attackers has increased (effect size = 0.66 ± 1.13) but has decreased in central midfielders (effect size = 0.83). The body fat of defenders has also fallen (effect size = 0.55 ± 0.95). Spanish high-level goalkeepers, lateral midfielders, and attackers were taller than their semi-professional player counterparts (effect size = 1.20 ± 1.98). Body fat did not determine promotion from a reserve team to high-level soccer, but height may be an advantage for several playing positions. The assessment of the anthropometric profile and the application of interventions should be designed according to the playing position.