High-intensity Actions in Elite Soccer: Current Status and Future Perspectives.

Over the years, soccer has become more physically demanding; the number and frequency of high-intensity actions have increased, and these activities are decisive in determining the match outcome. Importantly, the reductionist approach commonly used to analyze high-intensity actions does not contemplate a more contextualized perspective on soccer performance. Traditionally, most investigations have only provided quantitative data regarding sprints (i. e. time, distances, frequency) without examining "how" (e. g. type of trajectory or starting position) and "why" (e. g. tactical role) soccer players sprint. In fact, other high-intensity actions, apart from running, are not even mentioned (i. e. curve sprints, change of direction, and specific-jump tasks). This has led to the use of tests and interventions that do not accurately reflect real game actions. Given the true technical-tactical-physical demands of each playing position, this narrative review collected a wide-spectrum of current soccer-related articles and provided a discussion regarding high-intensity actions, with a positional-based approach. In this narrative review, practitioners are encouraged to contemplate and consider the different elements that characterize high-intensity actions in soccer, in order to assess and train soccer players under a more sport-specific and integrative perspective.

Effectiveness of Conservative Interventions After Acute Hamstrings Injuries in Athletes: A Living Systematic Review.

BACKGROUND: Hamstrings injuries are common in sports and the reinjury risk is high. Despite the extensive literature on hamstrings injuries, the effectiveness of the different conservative (i.e., non-surgical) interventions (i.e., modalities and doses) for the rehabilitation of athletes with acute hamstrings injuries is unclear. OBJECTIVE: We aimed to compare the effects of different conservative interventions in time to return to sport (TRTS) and/or time to return to full training (TRFT) and reinjury-related outcomes after acute hamstrings injuries in athletes. DATA SOURCES: We searched CINAHL, Cochrane Library, EMBASE, PubMed, Scopus, SPORTDiscus, and Web of Science databases up to 1 January, 2022, complemented with manual searches, prospective citation tracking, and consultation of external experts. ELIGIBILITY CRITERIA: The eligibility criteria were multi-arm studies (randomized and non-randomized) that compared conservative treatments of acute hamstrings injuries in athletes. DATA ANALYSIS: We summarized the characteristics of included studies and conservative interventions and analyzed data for main outcomes (TRTS, TRFT, and rate of reinjuries). The risk of bias was judged using the Cochrane tools. Quality and completeness of reporting of therapeutic exercise programs were appraised with the i-CONTENT tool and the certainty of evidence was judged using the GRADE framework. TRTS and TRFT were analyzed using mean differences and the risk of reinjury with relative risks. RESULTS: Fourteen studies (12 randomized and two non-randomized) comprising 730 athletes (mostly men with ages between 14 and 49 years) from different sports were included. Nine randomized studies were judged at high risk and three at low risk of bias, and the two non-randomized studies were judged at critical risk of bias. Seven randomized studies compared exercise-based interventions (e.g., L-protocol vs C-protocol), one randomized study compared the use of low-level laser therapy, and three randomized and two non-randomized studies compared injections of platelet-rich plasma to placebo or no injection. These low-level laser therapy and platelet-rich plasma studies complemented their interventions with an exercise program. Only three studies were judged at low overall risk of ineffectiveness (i-CONTENT). No single intervention or combination of interventions proved superior in achieving a faster TRTS/TRFT or reducing the risk of reinjury. Only eccentric lengthening exercises showed limited evidence in allowing a shorter TRFT. The platelet-rich plasma treatment did not consistently reduce the TRFT or have any effect on the risk of new hamstrings injuries. The certainty of evidence was very low for all outcomes and comparisons. CONCLUSIONS: Available evidence precludes the prioritization of a particular exercise-based intervention for athletes with acute hamstrings injuries, as different exercise-based interventions showed comparable effects on TRTS/TRFT and the risk of reinjuries. Available evidence also does not support the use of platelet-rich plasma or low-level laser therapy in clinical practice. The currently available literature is limited because of the risk of bias, risk of ineffectiveness of exercise protocols (as assessed with the i-CONTENT), and the lack of comparability across existing studies. CLINICAL TRIAL REGISTRATION: PROSPERO CRD42021268499 and OSF ( https://osf.io/3k4u2/ ).

Is there association between cutting and jump-landing movement quality in semi-professional football players? Implications for ACL injury risk screening.

OBJECTIVES: To investigate the relationship between the Landing Error Scoring System (LESS) and Cutting Movement Assessment Score (CMAS) to evaluate movement quality, their intra- (INTRAob) and inter-observer (INTERob) reliability, and the comparison between the two drop vertical jump (DVJ) landings (1st and 2nd). DESIGN: Cross-sectional. PARTICIPANTS: 42 male semi-professional soccer players performed three trials of DVJ and 70° change of direction with a ball located as an external focus. MAIN OUTCOME MEASURES: Movement quality was evaluated through 2D video footage using the CMAS and LESS, screened by two observers. Relational, comparative and reliability analyses were conducted. RESULTS: Both tools showed moderate to substantial (ICC = 0.58-0.71), and substantial to almost perfect (ICC = 0.68-0.87) INTRAob and INTERob reliability, respectively. No significant associations were found among CMAS, LESS 1st and 2nd for either scores or risk profiles (r = -0.158-0.202, p > 0.05). LESS 2nd was moderately higher (ES = 0.80-0.83, p = 0.002-0.007) than 1st scores. CONCLUSIONS: CMAS and LESS are reliable tools to evaluate movement quality, although evaluations should be preferably performed by the same observer; ACL injury risk profile's is task-dependent; both landings of the DVJ should be assessed as they represent different biomechanical and neuromuscular control deficits.

Effect of ball inclusion on jump performance in soccer players: a biomechanical approach.

OBJECTIVE: In soccer, vertical jump means jumping toward a ball. Since no vertical jump test includes the ball as a reference element, the effect that the ball would have in a vertical jump test is unknown. The aim of this study was to examine the biomechanical differences between run-up vertical jump measurements without (Run-up Vertical Jump) and with ball inclusion (Heading Test). METHODS: Twelve semi- and professional soccer players were recruited. Athletes performed both jump tests in a biomechanical laboratory, where kinetic and spatiotemporal variables were collected and compared using a Student's dependent t-test for paired samples. RESULTS: Overall, players performed a different jumping strategy during the heading test compared to the run-up vertical jump, exhibiting: 1) higher horizontal velocity during initial contact (+45.3%, P ≤ .001), 2) shorter contact time, greater rate of force development, and total impulse during push-off (+27.5%, +53%, and +10.6%, respectively, P ≤ .008), 3) higher CoM horizontal and resultant velocity during take-off (+76.1% and 20.5%, respectively, P ≤ .001), 4) better vertical jump performance (+4.3%, P ≤ .0001), and 5) larger body angle rotation during landing (+63.3%, P = .006), compared to run-up vertical jump (effect size: 0.78 to 3.7). CONCLUSION: In general, soccer players display greater vertical jump heights in heading test, which highlights the importance of including an overhead ball during soccer-specific jump tests. Coaches and practitioners are encouraged to assess, and perhaps develop, the jumping ability of soccer players using a suspended ball as a specific target.

How does curve sprint evolve across different age categories in soccer players?

Research has shown that soccer players regularly execute curved sprints during matches. The purpose of this study was to determine the age-related effects on curve sprint (CS) performance to both sides, asymmetry, and association with linear sprint (LS). Eighty-four soccer players (aged 16.1 ± 1.6 categorized in U15, U17, and U20) were recruited, who performed CS and LS tests. One-way analysis of variance (ANOVA) and effect size (ES) were used to compare CS performance between age categories, and relationships between physical performance measures were calculated using Pearson's correlation coefficient. The main findings of this study were that: 1) there were significant differences in the "good" side CS among age groups (p < 0.001; ES from moderate to large), but not in the "weak" side CS, 2) curve asymmetry was significantly higher in U20 than U15 (p < 0.05; ES large) and U17 players (p < 0.05; ES moderate), and 3) relationships between CS and LS times decreased with age (from significant and very large [p < 0.001] to non-significant and smallmoderate [p > 0.05]). This study highlights the importance of assessing and training CS in different age categories, an action that becomes less correlated with LS as age increases, with the aim of mitigating the increase in asymmetries as a result of the specialization process, focusing interventions mainly on improving the CS "weak" side.

The Safe Landing warm up technique modification programme: An effective anterior cruciate ligament injury mitigation strategy to improve cutting and jump-movement quality in soccer players.

The objective of the study was to evaluate the effectiveness of the Safe Landing (SL), a 6-week technique-modification (TM) programme, on cutting and jump-landing movement quality in football players. In a non-randomized design, 32 male semi-professional football players from two Spanish clubs participated in the study: one served as the control group (CG, n = 11), while the other performed the SL (n = 15). Performance and movement quality of drop vertical jump and 70º change of direction (COD70) were evaluated through 2D video footage pre- and post-intervention. In such tasks, the Landing Error Scoring System for first (LESS1) and second (LESS2) landings, and the Cutting Movement Assessment Score (CMAS) were used for assessing movement quality. Pre-to-post changes and baseline-adjusted ANCOVA were used. Medium-to-large differences between groups at post-test were shown in CMAS, LESS1 and LESS2 (p < 0.082, Õ²2 = 0.137-0.272), with small-to-large improvements in SL (p < 0.046, ES=0.546-1.307), and CG remaining unchanged (p > 0.05) pre-to-post. In COD70 performance, large differences were found between groups (p < 0.047, Õ²2 = 0.160-0.253), with SL maintaining performance (p > 0.05, ES=0.039-0.420), while CG moderately decreasing performance (p = 0.024, ES=0.753) pre-to-post. The SL is a feasible and effective TM program to improve movement quality and thus potential injury risk in cutting and landing, while not negatively affecting performance.

Exercise-Based Training Strategies to Reduce the Incidence or Mitigate the Risk Factors of Anterior Cruciate Ligament Injury in Adult Football (Soccer) Players: A Systematic Review.

Anterior cruciate ligament (ACL) is one of the most concerning injuries for football players. The aim of this review is to investigate the effects of exercise-based interventions targeting at reducing ACL injury rate or mitigating risk factors of ACL injury in adult football players. Following PRISMA guidelines, a systematic search was conducted in CINAHL, Cochrane Library, PubMed, Scopus, SPORTDiscus and Web of Science. Studies assessing the effect of exercise-based interventions in ACL injury incidence or modifiable risk factors in adult football players were included. 29 studies evaluating 4502 male and 1589 female players were included (15 RCT, 8 NRCT, 6 single-arm): 14 included warm-up, 7 resistance training, 4 mixed training, 3 balance, 1 core stability and 1 technique modification interventions. 6 out of 29 studies investigated the effect of interventions on ACL injury incidence, while the remaining 23 investigated their effect on risk factors. Only 21% and 13% studies evaluating risk of injury variables reported reliability measures and/or smallest worthwhile change data. Warm-up, core stability, balance and technique modification appear effective and feasible interventions to be included in football teams. However, the use of more ecologically valid tests and individually tailored interventions targeting specific ACL injury mechanisms are required.

The Hamstrings: Anatomic and Physiologic Variations and Their Potential Relationships With Injury Risk.

The incidence and recurrence of hamstrings injuries are very high in sports, posing elevated performance and financial-related costs. Attempts to identify the risk factors involved in predicting vulnerability to hamstrings injury is important for designing exercise-based programs that aim to mitigate the rate and severity of hamstrings injuries and improve rehabilitation strategies. However, research has shown that non-modifiable risk factors may play a greater role than modifiable risk factors. Recognizing non-modifiable risk factors and understanding their implications will afford the prescription of better suited exercise programs, i.e., that are more respectful of the individual characteristics. In a nutshell, non-modifiable risk factors can still be acted upon, even if indirectly. In this context, an underexplored topic is how intra and inter- individual anatomic and physiologic variations in hamstrings (e.g., muscle bellies, fiber types, tendon length, aponeurosis width, attachment sites, sex- and age-related differences) concur to alter hamstrings injuries risk. Some anatomic and physiologic variations may be modifiable through exercise interventions (e.g., cross-sectional area), while others may not (e.g., supernumerary muscle bellies). This apparent dichotomy may hide a greater complexity, i.e., there may be risk factors that are partially modifiable. Therefore, we explored the available information on the anatomic variations of the hamstrings, providing a deeper insight into the individual risk factors for hamstrings injuries and contributing with better knowledge and potential applications toward a more individualized exercise prescription.

Curve sprinting in soccer: relationship with linear sprints and vertical jump performance.

We examined the relationships among linear speed, vertical jumping ability and curve sprint (CS) performance. Moreover, the correlations between linear and curvilinear sprint velocities and CS deficit were tested. Twenty-eight under-20 soccer players performed squat and countermovement jumps, 17-m linear sprint (with split times at 5 and 10 m), and a CS test for both sides. For the first time, the new proposed CS deficit was calculated as the difference between 17-m velocity and CS test velocity. Pearson's product moment of correlation was performed to determine the relationships among the distinct variables tested. Significance level was set at P < 0.05. Large to very large relationships between linear sprint speed and CS performance were observed, on both the "good" and "weak" sides. In addition, moderate to large correlations between linear and curve sprint abilities and vertical jumps were found. Finally, the CS deficit was negatively associated with the CS good side performance. Linear sprint and CS velocities for both good and weak sides were closely related. The CS deficit was only related to the CS weak side performance, and the vertical jumping ability was significantly associated with both linear and curvilinear sprint velocities. The present results suggest that training methods capable of improving linear sprint and vertical jumping abilities may also improve CS performance.

Curve Sprinting in Soccer: Kinematic and Neuromuscular Analysis.

Sprinting in curvilinear trajectories is an important soccer ability, corresponding to ~85% of the actions performed at maximum velocity in a soccer league. We compared the neuromuscular behavior and foot contact-time between outside leg and inside leg during curve sprinting to both sides in soccer players. Nine soccer players (age=23±4.12 years) performed: 3×Sprint linear, 3×Sprint right curve, and 3×Sprint left curve. An ANOVA with repeated measures was used to compare the differences between inside and outside leg, and Cohen's d was used to calculate the effect-size. Considering the average data, the performance classification (from best to worst) was as follows: 1. Curve "good" side (2.45±0.11 s), 2. Linear (2.47±0.13 s), and 3. Curve "weak" side (2.56±0.17 s). Comparing linear with curve sprinting, inside leg recorded significant differences ("good" and "weak"; effect size=1.20 and 2, respectively); in contrast, for outside leg, there were no significant differences ("good" and "weak"; effect size=0.30 and 0.49, respectively). Electromyography activity showed significant differences (p≤0.05) during curve sprinting between outside (higher in biceps femoris and gluteus medius) and inside leg (higher activity in semitendinosus and adductor). In summary, inside and outside leg play different roles during curved sprints, but inside leg is more affected by the change from straight to curve sprint.