Effects of two different small-sided games protocols on physiological parameters of professional soccer players

The aim of the present study was to evaluate the effect of two different small-sided game protocols on the internal and external training parameters of professional soccer players. Twenty-two (N = 22) Greek Superleague 2 team players (age: 28.69 ± 3.4yr.; stature: 179.0 ± 25 cm; body mass: 76.0 ± 5.6 kg; body fat: 7.68 ± 1.5 %) participated in this study. The small-sided games (SSGs) included two research protocols+: A) 6+6 vs 6+6+2GK (45x40 m; 150m2 per player) with a duration of 4x4 min and B) 10 vs 10+2GK (75x65 m; 244 m2 per player) with a duration of 4x8min. The heart rate of the players, the covered distances, the amount of sprints and the number of accelerations/decelerations were recorded during the above protocols via short-range radio telemetry (Polar Team Sports System). The t-test (paired samples) was used to compare the differences between the two SSGs protocols. The results showed that the 6+6 vs 6+6+2GK SSGs induced significantly higher heart rate in relation to the 10 vs 10+2GK SSGs (p < .05). Furthermore, during the 10 vs 10+2GK SSGs the players covered more distances with high speed, while during the 6+6 vs 6+6+2GK SSGs a great number of accelerations and decelerations were recorded. Summarizing, the studied SSGs protocols resulted in different physical adaptations regarding the intensity, endurance and strength of the professional players. Thus, the trainers should carefully select the appropriate program focusing on the orientation of their training and the expected results

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

The impact of short periods of match congestion on injury risk and patterns in an elite football club

Background: The effect of fixture congestion on injury rates and patterns has received scarce attention in elite football and existing investigations have not accounted for player rotation or examined the temporal distribution and potential cause of injuries. Aim: To prospectively investigate the epidemiology of injury during short periods of fixture congestion in a professional football club. Methods: Over a 6-season period, exposure time and injury data were compared in the same players (n=25 [14 individuals]) when participating in two frequently occurring short congested fixture cycles in comparison to match-play outside these cycles. 1) two successive matches separated by an interval totalling ≤3days calculated immediately from the end of play in match 1 to the beginning of play in match 2; 2) three successive matches separated by ≤4-day intervals commencing the day immediately after each match. Results: In 2-match congestion cycles, incidence rate ratios (IRR) showed there was a higher risk of injury in the final 15-minutes of play in the second match in comparison to match-play outside the cycles (IRR: 3.1 [95% CI 1.1 to 9.3], p=0.0400). A greater risk of injury overall (IRR: 2.0 [95% CI 1.1 to 3.8], p=0.0345) and in the 1st-half of play (2.6 [1.1 to 6,5], p=0.0386), and risk of ankle sprains (10.4 [95% CI 1.9 to 57.9], p=0.0068) and non-contact injuries due to a ‘change in direction’ (IRR: 7.8 [1.3 to 46.8], p=0.0243) was observed in the final match of 3-match congestion cycles in comparison to match-play outside the cycles. Conclusion: Injury rates and patterns were affected in the same elite football players when competing in short congested fixture cycles in comparison to match-play outside the cycles

COMPARISON OF PHYSIOLOGICAL RESPONSES BETWEEN INTERVAL METHOD, 8V8 AND 4V4 GAMES AND TECHNICAL-TACTICAL EXERCISE IN SOCCER TRAINING

Purpose: Football is a sport that requires strong player demands. During the workout of improving the endurance are used exercises with or without the ball as well as racing games. In the present study we analyzed the burden of 4 different types of exercise(intermittent without the ball, 8v8 game, 4v4 game, and technical exercises) to determine which kind is best suited for improving the specific endurance. Material: The sample was 5 professional players (mean ± SD) of age (26± 2.9 years), height (1.79 ± 0,03m) and body weight (75± 3 kg). Prior to the experiment, a Test to determine the anaerobic threshold was performed. Measurements of lactic acid were made by using the Dr Lange photometer, while heart rate measurements by using POLARFT60 portable heart ratemeters. Results: The assumption of normal distribution was verified using the Kolmogorov-Smirnov test and it was found that in all variables the data follows the normal distribution. For the statistical treatment of the data a Analysis of Variance for repeated measure was used and for the detection of statistically significant differences between the measurement conditions was used the LSD multiple comparison test. The level of significance was defined as p4mmol lactic acid (F(3,12)= 21,331 p<0,05). c) in the min of the heart rate at 3-4 mmol lactic acid (F(3,12)= 3,584, p<0,05) d) in the min of heart rate at 2-3mmol lactic acid (f(3,12= 4,310,p <0,05) and e) averages of the heart rate relative to ANK (F (3,12)= 25,404, p<0,05). Conclusion: It seems that the 4 different types of exercise cause different metabolic processes of lactic acid production as well as different heart rate responses. The intermittent and 4v4 game schedule is better suited to improving the endurance the 8v8 game is suitable for improving aerobic endurance, while technical-tactical exercises do not produce sufficient stimuli to improve endurance but involve speed stimuli

The Influence of Recovery and Training Phases on Body Composition, Peripheral Vascular Function and Immune System of Professional Soccer Players

Professional soccer players have a lengthy playing season, throughout which high levels of physical stress are maintained. The following recuperation period, before starting the next pre-season training phase, is generally considered short but sufficient to allow a decrease in these stress levels and therefore a reduction in the propensity for injury or musculoskeletal tissue damage. We hypothesised that these physical extremes influence the body composition, blood flow, and endothelial/immune function, but that the recuperation may be insufficient to allow a reduction of tissue stress damage. Ten professional football players were examined at the end of the playing season, at the end of the season intermission, and after the next pre-season endurance training. Peripheral blood flow and body composition were assessed using venous occlusion plethysmography and DEXA scanning respectively. In addition, selected inflammatory and immune parameters were analysed from blood samples. Following the recuperation period a significant decrease of lean body mass from 74.4±4.2 kg to 72.2±3.9 kg was observed, but an increase of fat mass from 10.3±5.6 kg to 11.1±5.4 kg, almost completely reversed the changes seen in the pre-season training phase. Remarkably, both resting and post-ischemic blood flow (7.3±3.4 and 26.0±6.3 ml/100 ml/min) respectively, were strongly reduced during the playing and training stress phases, but both parameters increased to normal levels (9.0±2.7 and 33.9±7.6 ml/100 ml/min) during the season intermission. Recovery was also characterized by rising levels of serum creatinine, granulocytes count, total IL-8, serum nitrate, ferritin, and bilirubin. These data suggest a compensated hypo-perfusion of muscle during the playing season, followed by an intramuscular ischemia/reperfusion syndrome during the recovery phase that is associated with muscle protein turnover and inflammatory endothelial reaction, as demonstrated by iNOS and HO-1 activation, as well as IL-8 release. The data provided from this study suggest that the immune system is not able to function fully during periods of high physical stress. The implications of this study are that recuperation should be carefully monitored in athletes who undergo intensive training over extended periods, but that these parameters may also prove useful for determining an individual's risk of tissue stress and possibly their susceptibility to progressive tissue damage or injury

Monitoring of post-match fatigue in professional soccer: Welcome to the real world

Participation in soccer match-play leads to acute and transient subjective, biochemical, metabolic and physical disturbances in players over subsequent hours and days. Inadequate time for rest and regeneration between matches can expose players to the risk of training and competing whilst not entirely recovered. In professional soccer, contemporary competitive schedules can require teams to compete in-excess of 60 matches over the course of the season while periods of fixture congestion occur prompting much attention from researchers and practitioners to the monitoring of fatigue and readiness to play. A comprehensive body of research has investigated post-match acute and residual fatigue responses. Yet the relevance of the research for professional soccer contexts is debatable notably in relation to the study populations and designs employed. Monitoring can indeed be invasive, expensive, time-inefficient and difficult to perform routinely and simultaneously in a large squad of regularly competing players. Uncertainty also exists regarding the meaningfulness and interpretation of changes in fatigue response values and their functional relevance, and practical applicability in the field. The real-world need and cost-benefit of monitoring must be carefully weighed up. In relation to professional soccer contexts, this opinion paper intends to: 1) debate the need for PMF monitoring, 2) critique the real-world relevance of the current research literature, 3) discuss the practical burden relating to measurement tools and protocols and the collection, interpretation and application of data in the field, and, 4) propose future research perspectives

Effects of a competitive soccer match on jump performance and interlimb asymmetries in elite academy soccer players

The purpose of the present study was to investigate the effects of a competitive soccer match on jump performance and inter-limb asymmetries over incremental time points during a 72-hour (h) period. Fourteen elite adolescent players from a professional English category three academy performed single leg countermovement jumps (SLCMJ) pre, post, 24, 48, and 72-h post-match on a single force platform. Eccentric impulse, concentric impulse, peak propulsive force, jump height, peak landing force, and landing impulse were monitored throughout. Inter-limb asymmetries were also calculated for each metric as the percentage difference between limbs. Significant negative changes (p < 0.05) in jump performance were noted for all metrics at all time points, with the exception of jump height. Inter-limb asymmetries were metric-dependent and showed very large increases, specifically post-match, with a trend to reduce back towards baseline values at the 48-h time point for propulsive-based metrics. Asymmetries for landing metrics did not peak until the 24-h time point and again reduced towards baseline at 48-h. The present study highlights the importance of monitoring distinct jump metrics, as jump height alone was not sensitive enough to show significant changes in jump performance. However, inter-limb asymmetries were sensitive to fatigue with very large increases post-match. More frequent monitoring of asymmetries could enable practitioners to determine whether existing imbalances are also associated with reductions in physical performance or increased injury risk

The assessment of neuromuscular fatigue during 120 min of simulated soccer exercise

Purpose This investigation examined the development of neuromuscular fatigue during a simulated soccer match incorporating a period of extra time (ET) and the reliability of these responses on repeated test occasions. Methods Ten male amateur football players completed a 120 min soccer match simulation (SMS). Before, at half time (HT), full time (FT), and following a period of ET, twitch responses to supramaximal femoral nerve and transcranial magnetic stimulation (TMS) were obtained from the knee-extensors to measure neuromuscular fatigue. Within 7 days of the first SMS, a second 120 min SMS was performed by eight of the original ten participants to assess the reliability of the fatigue response. Results At HT, FT, and ET, reductions in maximal voluntary force (MVC; −11, −20 and −27%, respectively, P ≤ 0.01), potentiated twitch force (−15, −23 and −23%, respectively, P < 0.05), voluntary activation (FT, −15 and ET, −18%, P ≤ 0.01), and voluntary activation measured with TMS (−11, −15 and −17%, respectively, P ≤ 0.01) were evident. The fatigue response was robust across both trials; the change in MVC at each time point demonstrated a good level of reliability (CV range 6–11%; ICC2,1 0.83–0.94), whilst the responses identified with motor nerve stimulation showed a moderate level of reliability (CV range 5–18%; ICC2,1 0.63–0.89) and the data obtained with motor cortex stimulation showed an excellent level of reliability (CV range 3–6%; ICC2,1 0.90–0.98). Conclusion Simulated soccer exercise induces a significant level of fatigue, which is consistent on repeat tests, and involves both central and peripheral mechanisms