A systematic literature search was conducted in the Scopus and PubMed databases. The search strategy was developed based on the PICOS framework and combined using Boolean operators (“AND,” “OR”). The main search strings used were as follows:

(“FIFA 11+” OR “FIFA eleven plus” OR “11+ injury prevention”) AND (“lower limb function” OR “range of motion” OR ROM OR “hamstring strength” OR “knee extension” OR “hip rotation” OR “neuromuscular performance”) AND (“athlete” OR “soccer player” OR “football player” OR “sport”).

The search was limited to peer-reviewed articles in English that were available in full text. There were no restrictions on publication year to ensure comprehensive literature coverage. The search strategy was slightly adjusted to the characteristics of each database to maximize search sensitivity.

Study selection was guided by predefined inclusion and exclusion criteria based on the PICOS framework. Eligible studies included original research articles employing randomized controlled trials, controlled trials, cohort studies, or quasi-experimental designs. Participants were required to be athletes or physically active individuals, regardless of age, sex, or competitive level.

Studies were included if they implemented the FIFA 11+ program (full or modified versions) and compared it with standard training, usual warm-up routines, or no specific injury-prevention intervention. To be eligible, studies had to report at least one relevant lower limb functional outcome, including range of motion, knee extension, hip internal or external rotation, or hamstring muscle strength.

Studies were excluded if they were reviews, editorials, conference abstracts without full text, case studies, or single-subject reports. Articles focusing solely on injury incidence without reporting functional or strength-related outcomes, studies not involving the FIFA 11+ program, and non-English publications were also excluded.

The study selection process was conducted in several stages in accordance with the PRISMA 2020 guidelines (Figure 1). Two independent reviewers separately screened the titles and abstracts to identify relevant studies. Studies that passed the initial stage were then reviewed in full text by the same two reviewers to ensure compliance with the established inclusion and exclusion criteria. Any differences of opinion between reviewers were resolved through discussion until consensus was reached. If necessary, the final decision was made through joint discussion.

The methodological quality and risk of bias of the included studies were evaluated using the Newcastle–Ottawa Scale (NOS). NOS was chosen because it allows for consistent and transparent assessment across heterogeneous study designs, including randomized and non-randomized studies, which form the basis of the evidence included in this review.

The NOS evaluates study quality in three domains: study group selection, group equivalence, and outcome assessment. Each study is assigned a maximum score of nine points. Studies with a score of 7–9 points are classified as having a low risk of bias, scores of 5–6 points as moderate risk, and studies with a score of ≤4 points as high risk of bias.

The quality assessment was conducted to support the interpretation of findings and provide an overview of the rigor of the available evidence methodology. The results of the quality assessment are presented in Table 1.

The Newcastle–Ottawa Scale (NOS) evaluates study quality based on three domains: selection (maximum 4 points), comparability (maximum 2 points), and outcome assessment (maximum 3 points). Studies scoring 7–9 points were considered low risk of bias, 5–6 points moderate risk, and ≤4 points high risk of bias

Due to substantial heterogeneity across studies in terms of study design, comparator types, outcome definitions, measurement methods, and reporting formats, a quantitative meta-analysis was not feasible. Therefore, a qualitative narrative synthesis was conducted.

Findings were synthesized and reported according to outcome categories, including range of motion, knee extension, hip internal and external rotation, and hamstring muscle strength. Patterns of results, direction of effects, and potential mechanisms underlying observed changes were discussed. This approach allowed for a comprehensive interpretation of the evidence while maintaining methodological rigor and transparency.

The study selection process is summarized in the PRISMA 2020 flow diagram. A total of 850 records were identified through database searching (Scopus and PubMed). After removing duplicate records and records excluded for other reasons (n = 111), 739 records were screened based on titles and abstracts. Of these, 725 records were excluded as they did not meet the predefined inclusion criteria. The remaining 14 full-text articles were assessed for eligibility, and all were deemed eligible and included in the qualitative synthesis. No full-text articles were excluded at the eligibility stage.

The 14 included studies comprised a range of experimental and quasi-experimental designs, including randomized controlled trials and controlled intervention studies. Participants were predominantly athletes or physically active individuals, with most studies involving soccer players, reflecting the original target population of the FIFA 11+ program. Study durations varied across investigations, ranging from short-term interventions to multi-week training programs.

Interventions consisted of the full FIFA 11+ program or modified versions, while comparators included usual warm-up routines, standard training, or alternative warm-up protocols. Outcome assessments were conducted pre- and post-intervention, with post-intervention values prioritized for synthesis. Overall, the included studies represented diverse populations, intervention durations, and comparator conditions, contributing to methodological heterogeneity.

The included studies reported a variety of lower limb functional outcomes, including range of motion (ROM), knee extension, hip internal and external rotation, and hamstring muscle strength. ROM outcomes were commonly assessed using goniometric measurements, either under passive conditions or during weight-bearing tasks. Muscle strength outcomes were predominantly evaluated using isokinetic dynamometry, with angular velocities varying across studies.

Hamstring muscle strength was the most frequently reported outcome, followed by joint ROM measures. Considerable heterogeneity was observed in outcome definitions, measurement instruments, testing protocols, and reporting formats. This variability limited direct quantitative comparison across studies and supported the use of a qualitative narrative synthesis approach.

The methodological quality of the included studies, assessed using the Newcastle–Ottawa Scale (NOS), ranged from moderate to low risk of bias. Overall, the majority of studies demonstrated moderate methodological quality, with total NOS scores typically between 5 and 6 points, indicating acceptable rigor for narrative synthesis. Several studies achieved higher quality ratings (NOS scores ≥7), reflecting stronger methodological characteristics, particularly in terms of participant selection and outcome assessment.

Across the included studies, the selection domain generally received favorable scores, as most investigations clearly defined eligibility criteria and employed appropriate participant recruitment methods. In contrast, comparability between groups was a recurring methodological limitation, as many studies did not fully control for potential confounding variables or lacked rigorous randomization procedures. The outcome domain was commonly rated as moderate, with most studies reporting validated measurement tools and post-intervention outcomes, although blinding of outcome assessors was infrequently described.

Taken together, the quality assessment suggests that the included evidence provides a reasonable methodological foundation for qualitative synthesis, while highlighting the need for future studies with improved control of confounding factors and more robust experimental designs.

Overall, the narrative synthesis indicated that the FIFA 11+ program was associated with improvements in lower limb functional outcomes across multiple domains. Several studies reported increases in hamstring muscle strength, particularly when assessed using isokinetic protocols, suggesting favorable neuromuscular adaptations. Improvements in joint range of motion, including hip and knee-related measures, were also observed, although the magnitude and consistency of effects varied across studies.

The heterogeneity in study design, intervention implementation, outcome measures, and comparator conditions precluded quantitative pooling of results. Nevertheless, the direction of findings across studies generally supported a beneficial role of the FIFA 11+ program in enhancing lower limb functional performance. These findings provide a coherent qualitative evidence base while highlighting the need for future studies employing standardized outcome measures and more rigorous experimental designs.

Several included studies reported improvements in joint range of motion, particularly at the hip, knee, and ankle, following implementation of the FIFA 11+ program (Arsenis et al., 2020; Ayala et al., 2017; Brito et al., 2010; Soussi et al., 2025; Sumartiningsih et al., 2022). These findings suggest that the program’s dynamic warm-up structure, which incorporates progressive mobility and controlled joint excursions, may contribute to enhanced flexibility and joint mobility.

The observed ROM improvements may be explained by the dynamic stretching and movement preparation elements of the FIFA 11+ program (Bizzini & Dvorak, 2015). Dynamic warm-up activities have been shown to increase muscle–tendon compliance and joint mobility without negatively affecting neuromuscular performance (Behm & Chaouachi, 2011). Over repeated training sessions, such activities may promote chronic adaptations in soft tissue extensibility and movement efficiency.

However, ROM-related findings were not entirely consistent across studies, likely due to heterogeneity in measurement techniques, such as passive versus weight-bearing assessments, and differences in joint-specific testing protocols. This variability limits direct comparisons and highlights the need for standardized ROM assessment methods in future FIFA 11+ research.

Evidence regarding the effects of the FIFA 11+ program on knee extension outcomes was more limited compared with other functional measures. Where reported, improvements in knee extension strength or control were modest and varied across studies (Daneshjoo et al., 2012; Daneshjoo et al., 2013; Soussi et al., 2025). These mixed findings may reflect the fact that the FIFA 11+ program emphasizes neuromuscular control and movement quality rather than isolated quadriceps strengthening.

From a mechanistic perspective, improvements in knee extension-related function may be mediated through enhanced lower limb alignment, trunk stability, and neuromuscular coordination, rather than direct increases in maximal knee extensor strength. Previous research suggests that neuromuscular training can improve knee joint stability and force transmission efficiency even in the absence of large strength gains (Bahr & Krosshaug, 2005).The limited and heterogeneous reporting of knee extension outcomes underscores the need for clearer operational definitions and consistent testing approaches in future studies.

Several studies included in this review examined hip internal and external rotation, reporting improvements following FIFA 11+ implementation (Impellizzeri et al., 2013; Zhou et al., 2022). Enhanced hip rotational mobility is particularly relevant for sports involving cutting, pivoting, and directional changes, where hip joint mechanics play a crucial role in both performance and injury risk.

The FIFA 11+ program incorporates exercises targeting pelvic control, core stability, and multi-planar lower limb movements, which may indirectly influence hip rotational capacity (Impellizzeri et al., 2013; Zhou et al., 2022). Improved neuromuscular control around the hip joint may reduce excessive joint stiffness while promoting functional mobility (Mendiguchia & Brughelli, 2011).

Nevertheless, findings related to hip rotation were inconsistent across studies, likely due to differences in testing positions, examiner techniques, and participant characteristics. These inconsistencies further emphasize the importance of methodological standardization.

Among all functional outcomes assessed, hamstring muscle strength demonstrated the most consistent improvements following FIFA 11+ training. Multiple studies reported post-intervention increases in hamstring strength, typically measured using isokinetic dynamometry, suggesting favorable neuromuscular adaptations (Arsenis et al., 2020; Brito et al., 2010; Bukry et al., 2024; Danesjhoo et el., 2013).

The improvements in hamstring strength can be attributed to the eccentric and neuromuscular loading components embedded within the FIFA 11+ program. Exercises emphasizing controlled deceleration, trunk stabilization, and posterior chain engagement are known to enhance hamstring activation and force-producing capacity (Pun, 2020). Such adaptations are particularly relevant given the role of hamstring strength in sprinting performance and injury prevention.

Despite these positive findings, variability in testing velocities, contraction modes, and reporting practices limited direct comparison across studies. Nonetheless, the overall pattern of evidence supports a beneficial effect of the FIFA 11+ program on hamstring muscle function.

A key strength of this review is its systematic and transparent methodology, guided by PRISMA 2020 and prospectively registered in PROSPERO. The review comprehensively synthesized evidence across multiple lower limb functional domains, providing a broad perspective on the functional effects of the FIFA 11+ program beyond injury incidence alone. The use of a structured quality assessment tool further enhanced the rigor of the synthesis.

Several limitations should also be acknowledged. First, the included studies exhibited moderate methodological quality, with common limitations related to group comparability, randomization procedures, and blinding. Second, substantial heterogeneity in study design, outcome definitions, and measurement protocols precluded quantitative meta-analysis. Third, most studies focused on short- to medium-term interventions, limiting insight into the long-term functional effects of the FIFA 11+ program. These limitations reflect gaps in the existing literature rather than shortcomings of the present review and highlight important directions for future research.