The rotation strategy in high-level European soccer teams

The purpose of the present study was to examine the rotation strategy in high-level soccer teams during a sequence of three games per week (1st domestic, 2nd European and 3rd domestic). Data were collected during the 2014-15, 2015-16, 2016-17 and 2017-18 competitive season for the soccer teams that were qualified in the quarter finals of the Champions League. Regression analysis showed that when a large number of players participated in the initial list for the three games, more points in the domestic league were lost. Similarly, increasing the changes of players in the initial list between the 1st and the 3rd game and between the 2nd and the 3rd game a negative effect on the domestic league was observed. In contrast, a positive effect of the number of changes of players in the starting line between the 1st and the 2nd game, regarding the total points won, was found. As the average time of the substitutes participated in the game increases in all three games, the total points of the teams are reduced. The biggest time of changes in the 2nd game had a negative impact on the points of European games. In order to achieve a more efficient rotation, coaches should have a qualitative and competitive roster of players. Furthermore, coaches should try to apply different tactics in previous matches in order, as many players as possible, to maintain high levels of homogeneity and competing readiness

Biomechanical analysis of kicking and cutting maneuvers in soccer

The aim of the PhD thesis was to examine kicking and cutting maneuver tasks between men, women and pubertal amateur soccer players. For this purpose four (4) different studies were conducted. The 1st study compared instep soccer kicks between men, women and pubertal soccer players. The participants performed three (3) maximum kicks against a stationary soccer ball, while kinematic and kinetic parameters were recorded. Analysis of Variance showed significantly higher ball speed values, ankle linear velocity and angular displacement of the ankle for men compared to women and pubertal players. The vertical ground reaction forces were significantly higher for the pubertal players compared to men and women. The muscular strength differences and the differences of the linear velocity of the ankle seem to resulted in ball speed differences among the examined groups. The 2nd study compared side-step cutting maneuver tasks between men, women and pubertal soccer players. The participants after a two step approach performed a cutting task at a 45? cutting angle. Analysis of variance showed non-significant differences on the duration of the maneuvers and the knee flexion angle between the examined groups. In contrast, pubertal players demonstrated higher ground reaction forces compared to men and women. The results of the present study indicated that cutting maneuver tasks are extremely danger situations for knee injury. The pubertal players, however, seems to be in an increased injury potential compared to men and women. The 3rd study compared straight approach kicking tasks and kicking trials performed after a cutting (faking) maneuver task between men, women and pubertal soccer players. The participants performed five (5) straight approach instep kicks and five (5) kicks after a double cutting maneuver task. The results showed significantly lower ball speed values only for the pubertal players during the kicking tasks after cutting maneuver tasks (Ρ 0.05). Similarly, ankle, knee and hip linear velocities were not altered after fatigue (Ρ > 0.05). Only the hip angular displacement of the women was significantly lower after the fatigue protocol. Similarly, the results showed a significantly effect of fatigue only on selected ground reaction forces parameters. In conclusion, the kicking skill is an explosive movement that is well programmed on the central nervous system because of continuous training and seems that is difficult to be altered. The present PhD thesis showed that despite the performance differences regarding the ball speed, the kicking motion did not significantly differ between men and women, between different age levels and after the implementation of a specific fatigue protocol. Moreover, when the kicking motion is combined with another technique skill, such as the cutting maneuver, then the co-ordination demands increases in order better performance to be succeeded. Finally, cutting maneuver tasks seems to increase the load on the knee joint increasing the potential for a knee injury, with pubertal players being in a more danger situation.Ο σκοπός της παρούσας διδακτορικής διατριβής ήταν να εξετάσει το σουτ και τις αλλαγές κατεύθυνσης σε άνδρες, γυναίκες και παιδιά ποδοσφαιριστές. Γι’ αυτόν τον σκοπό πραγματοποιήθηκαν τέσσερις (4) επιμέρους εργασίες. Στην 1η εργασία συγκρίθηκαν λακτίσματα με την ραχιαία επιφάνεια του ποδιού ανάμεσα σε δέκα άνδρες, δέκα γυναίκες και δέκα παιδιά ποδοσφαιριστές. Ο καθένας από τους συμμετέχοντες εκτέλεσε τρία (3) μέγιστα λακτίσματα μιας σταθεροποιημένης μπάλας. Η Ανάλυση Διακύμανσης έδειξε στατιστικά σημαντικά μεγαλύτερες ταχύτητες απελευθέρωσης της μπάλας, μεγαλύτερη ταχύτητα της ποδοκνημικής και μεγαλύτερη πελματιαία κάμψη για τους άνδρες σε σχέση με τις γυναίκες και τα παιδιά. Οι κατακόρυφες δυνάμεις αντίδρασης του εδάφους ήταν υψηλότερες για τα παιδιά, ενώ οι πλάγιες και οι προσθιοπίσθιες δυνάμεις δεν διαφοροποιήθηκαν. Οι διαφορές στη μυϊκή δύναμη και η ταχύτητα της ποδοκνημικής κατά την επαφή με την μπάλα φαίνεται πως ευθύνονται για την υψηλότερη ταχύτητα της μπάλας στους άνδρες. Στην 2η εργασία εξετάστηκαν αλλαγές κατεύθυνσης του τρεξίματος ανάμεσα σε άνδρες, γυναίκες και παιδιά ποδοσφαιριστές. Ο καθένας από τους συμμετέχοντες εκτέλεσε αλλαγές κατεύθυνσης σε γωνία 45?. Η Ανάλυση Διακύμανσης δεν έδειξε σημαντικές διαφορές στη χρονική διάρκεια της κίνησης και στην κάμψη του γονάτου κατά το πάτημα για την αλλαγή κατεύθυνσης. Αντίθετα, τα παιδιά παρουσίασαν μεγαλύτερες δυνάμεις αντίδρασης του εδάφους και στους τρεις άξονες. Από τα αποτελέσματα φάνηκε πως οι αλλαγές κατεύθυνσης αποτελούν επικίνδυνες καταστάσεις τραυματισμού της άρθρωσης του γονάτου, με τα παιδιά να αντιμετωπίζουν ιδιαίτερα αυξημένο κίνδυνο. Στην 3η εργασία εξετάστηκαν σουτ με και χωρίς προσποίηση ανάμεσα σε άνδρες, γυναίκες και παιδιά. Καθένας από τους συμμετέχοντες εκτέλεσε λακτίσματα με την ραχιαία επιφάνεια του ποδιού και λακτίσματα μετά από διπλή προσποίηση. Τα αποτελέσματα έδειξαν στατιστικά σημαντική μείωση της ταχύτητας της μπάλας μόνο στα παιδιά μετά από λακτίσματα με προσποίηση. Οι γραμμικές ταχύτητες των αρθρώσεων παρουσίασαν σημαντική μείωση στα παιδιά κατά την εκτέλεση λακτισμάτων μετά από προσποίηση. Οι δυνάμεις αντίδρασης του εδάφους διαφοροποιήθηκαν στατιστικά σημαντικά μόνο στον πλάγιο άξονα για τα παιδιά. Τα αποτελέσματα έδειξαν πως τα παιδιά εμφάνισαν μικρότερη ταχύτητα της μπάλας κατά την εκτέλεση λακτισμάτων μετά από προσποίηση γεγονός που αποδίδεται στις μικρότερες ταχύτητες των αρθρώσεων κατά την επαφή με την μπάλα και στον μειωμένο συντονισμό των κινήσεων που δεν επέτρεψε τη μεταφορά ενέργειας από το ένα μέλος του σώματος στο άλλο. Στην 4η εργασία εξετάστηκε η επίδραση της κόπωσης κατά τη διάρκεια λακτισμάτων με και χωρίς προσποίηση σε άνδρες και γυναίκες ποδοσφαιριστές. Καθένας από τους συμμετέχοντες εκτέλεσε μέγιστα λακτίσματα με και χωρίς προσποίηση πριν και μετά την εφαρμογή ενός πρωτοκόλλου κόπωσης. Η Ανάλυση Διακύμανσης δεν έδειξε σημαντικές διαφοροποιήσεις στην ταχύτητα της μπάλας και στις γραμμικές ταχύτητες πριν και μετά την κόπωση για κανένα είδος λακτίσματος, ενώ μόνο η γωνιακή μετατόπιση του ισχίου των γυναικών παρουσίασε διαφορές μετά την εφαρμογή του πρωτοκόλλου κόπωσης. Μικρές, επίσης, μεταβολές των δυνάμεων αντίδρασης του εδάφους παρατηρήθηκαν πριν και μετά την κόπωση για τους άνδρες και τις γυναίκες. Τα αποτελέσματα έδειξαν πως το λάκτισμα αποτελεί μια εκρηκτική κίνηση, η οποία έχει προγραμματιστεί στον αθλητή εξαιτίας της συνεχούς επανάληψης, με αποτέλεσμα η διαταραχή του κινητικού προτύπου της κίνησης να είναι δύσκολη. Η διδακτορική διατριβή έδειξε πως παρά τις διαφορές στην επίδοση των αθλητών, όπως αυτή εκφράστηκε από την ταχύτητα απελευθέρωσης της μπάλας, η κίνηση του σουτ δεν διαφέρει σημαντικά ανάμεσα σε άνδρες και γυναίκες, ανάμεσα σε διαφορετικές ηλικιακές κατηγορίες και μετά από την εφαρμογή ενός πρωτοκόλλου κοπώσεως. Επίσης, όταν η κίνηση του σουτ συνδυάζεται με άλλες τεχνικές δεξιότητες, όπως είναι οι αλλαγές κατεύθυνσης, αυξάνονται οι απαιτήσεις συντονισμού προκειμένου να επιτευχθούν καλύτερες επιδόσεις. Τέλος, οι αλλαγές κατεύθυνσης φαίνεται πως επιβαρύνουν σημαντικά την άρθρωση του γονάτου αυξάνοντας τον κίνδυνο τραυματισμού, με τα παιδιά να βρίσκονται σε ιδιαίτερα επικίνδυνη θέσ

BIOMECHANICAL CHARACTERISTICS AND DETERMINANTS OF INSTEP SOCCER KICK

Good kicking technique is an important aspect of a soccer player. Therefore, understanding the biomechanics of soccer kicking is particularly important for guiding and monitoring the training process. The purpose of this review was to examine latest research findings on biomechanics of soccer kick performance and identify weaknesses of present research which deserve further attention in the future. Being a multiarticular movement, soccer kick is characterised by a proximal-to-distal motion of the lower limb segments of the kicking leg. Angular velocity is maximized first by the thigh, then by the shank and finally by the foot. This is accomplished by segmental and joint movements in multiple planes. During backswing, the thigh decelerates mainly due to a motion-dependent moment from the shank and, to a lesser extent, by activation of hip muscles. In turn, forward acceleration of the shank is accomplished through knee extensor moment as well as a motion-dependent moment from the thigh. The final speed, path and spin of the ball largely depend on the quality of foot-ball contact. Powerful kicks are achieved through a high foot velocity and coefficient of restitution. Preliminary data indicate that accurate kicks are achieved through slower kicking motion and ball speed value

EFFECTS OF SMALL-SIDED GAMES ON PHYSICAL CONDITIONING AND PERFORMANCE IN YOUNG SOCCER PLAYERS

The purpose of this study was to examine, first, the movement actions performed during two different small-sided games and, second, their effects on a series of field endurance and technical tests. Thirty-four young soccer players (age: 13 ± 0.9 yrs; body mass: 62.3 ± 15.1 kg; height: 1.65 ± 0.06 m) participated in the study. Small-sided games included three-a-side (3 versus 3 players) and six-a-side (6 versus 6 players) games consisting of 10 bouts of 4 min duration with 3 min active recovery between bouts. Soccer player performance was evaluated using five field tests: a) 30m sprint, b) throw-in for distance, c) Illinois Agility Test, d) dribbling the ball and e) horizontal jump before, in the middle and after the implementation of both game situations. Heart rate was monitored during the entire testing session. Each game was also filmed to measure soccer movements within the game. The ANOVA analysis indicated that the three-a- side games displayed significantly higher heart rate values compared with the six-a-side games (p < 0.05). The number of short passes, kicks, tackles, dribbles and scoring goals were significantly higher during the three-a-side compared with the six-a-side game condition (p < 0. 05) while players performed more long passes and headed the ball more often during the six-a-side (p < 0.05). After the three-a-side games, there was a significant decline in sprint and agility performance (p < 0.05), while after both game conditions significant alterations in the throw-in and the horizontal jump performance were observed (p < 0.05). The results of the present study indicated that three-a-side games provide higher stimulus for physical conditioning and technical improvement than six-a-side games and their use for training young soccer players is recommende

Evolution of Equipment in Electromobility and Autonomous Driving Regarding Safety Issues

Over the years, an increase in the traffic of electric and hybrid electric vehicles and vehicles with hydrogen cells is being observed, while at the same time, self-driving cars are appearing as a modern trend in transportation. As the years pass, their equipment will evolve. So, considering the progress in vehicle equipment over the years, additional technological innovations and applications should be proposed in the near future. Having that in mind, an analytical review of the progress of equipment in electromobility and autonomous driving is performed in this paper. The outcomes of this review comprise hints for additional complementary technological innovations, applications, and operating constraints along with proposals for materials, suggestions and tips for the future. The aforementioned hints and tips aim to help in securing proper operation of each vehicle part and charging equipment in the future, and make driving safer in the future. Finally, this review paper concludes with a discussion and bibliographic references

Elimination of PPV and PNRSV through thermotherapy and meristem-tip culture in nectarine

The plum pox virus (PPV) and prunus necrotic ringspot virus (PNRSV) cause serious disease problems in stone-fruit trees. In this work, the possibility of obtaining plant material free from these viruses through thermotherapy and meristem-tip culture from infected nectarine shoots (Prunus persica var. nectarina Max, cv. ''Arm King'') was studied. In addition, the detection of these viruses in in vitro cultures and young acclimatized plantlets with double antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA) and multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) was studied. Meristem-tip explants (0.8–1.3 mm) derived from sprouted buds of winter wood and spring shoots from field grown plants had a 2–5% regeneration response. However, application of thermotherapy to potted nectarine trees (3 weeks at a maximum temperature of 35°C) facilitated excision of longer meristem tips (1.3–2.0 mm) that resulted in a significantly higher regeneration response (38%) in woody plant medium (WPM) without plant growth regulators. Such explants formed multiple shoots with the addition of 8 M benzylaminopurine and 0.8 M indoleacetic acid. When they were tested for the presence of PPV and PNRSV, 86% and 81% were found to be virus-free as detected by DAS-ELISA and multiplex RT-PCR, respectively. Individual shoots excised from virus-free cultures readily rooted in vitro (half-strength WPM plus 2 M indolebutyric acid) and grew to plantlets. The combination of an efficient protocol for virus elimination and the establishment of highly sensitive diagnostics resulted in the production of nectarine plants free from PPV and PNRSV

Effect of 3 vs. 3 Soccer Small-Sided Game on Various Performance, Inflammatory, Muscle Damage and Hormonal Indicators in Semi-Professional Players

The purpose of this study was to examine the effect of a soccer small-sided game (SSG) on performance, inflammatory, muscle damage and hormonal indicators. Twenty-two male soccer players participated and were assigned to either experimental (EXP = 12) or control (CON = 10) groups. Subjective fatigue (RPE) and lactate (La¯) were measured during the SSG; vertical squat jump (SJ), 20-m sprint, creatine kinase (CK), interleukin-6 (IL-6), cortisol (C), and testosterone (T) were measured before (PRE), after (POST), 24 h, 48 h, and 72 h after the SSG in the EXP group. The heart rate during the SSG reached 92 ± 3% of their HRmax, whereas La¯ and RPE reached 13.02 ± 1.60 mmol·L−1 and 15 ± 1 after SSG, respectively. The IL-6, different among measurements (F (1.04, 11.50) = 504.82, p −1 [95%CI; 3.28–3.77]) after the SSG and returned to baseline 24 h later. The CK, different among measurements (F (1.76, 19.32) = 93.96, p −1 [95%CI; 466.01–607.15]) 24 h after the SSG and remained significantly higher than PRE condition in POST and up to 72 h later. The T/C ratio, significantly different among measurements (F (1.73, 19.05) = 12.12, p p < 0.05) and returned to baseline after 24 h. It seems that 48 h (at the most) after an SSG is adequate time for players to recover, and a high training load should be avoided sooner than 24 h after an SSG