Only severe Injuries are effectively reduced by muscles' injury prevention protocols in football players: A systematic review

Introduction

Muscle injury (MI) is the most common injury in football.¹ The incidence of total injuries varies between 1.06/1000 hours (hours) and 5.87/1000 hours of training and competition.² MI is typically caused by repeated eccentric muscular contractions.³ The relationship between eccentric muscular contraction and MI is confirmed by the lower occurrence of MI during cycling and swimming, two sports based almost exclusively on concentric muscle contraction.^4,5 Hamstring muscles are the most frequent site of MI in professional football, where they cause the highest number of absence days during the sporting season (25% of all absences due to injuries), with an average recovery time of nine days.^6,7

Eccentric strengthening is considered effective in the prevention of MI because it results from an eccentric strength deficit in comparison with the concentric force of hip extensors in elite sprinters.⁶ Among sports science researchers who aimed to develop a global and universal program for injury prevention, F-MARC conducted the first study on exercise-based prevention of football injuries, showing 21% fewer injuries in the intervention group (IG) than in the control group (CG).⁷ The interventions focused on improving the structure and content of the training by educating and supervising coaches and players. The program included preventive interventions, such as improvement of warm-up, regular cool-down, taping of unstable ankles, adequate rehabilitation, promotion of the spirit of fair play, and 10 sets of exercises. It is designed to improve coordination, stability of the ankle and knee, and flexibility and strength of the trunk, hip, and leg muscles. Subsequently, F MARC, in cooperation with international experts developed the FIFA11 (Federation Internationale Football Association).⁸

Evidence of the efficacy of this program has been reported in several studies.^9,10 Many trainers have judged that it is a lengthy program and that players find it difficult to adhere to it, given the absence of exercises involving the ball.⁹ Therefore, modifications were added; hence, FIFA11+.¹¹

For more than 10 years, researchers and researchers have been performing exercises to identify the most effective ones in MI prevention. Knowing the most effective program with evidence-based practice will help improve prevention measures and reduce the incidence of MI in football.

Method

The present research work is a systematic review of the biomedical literature to provide an analysis of the preventive effect of programs for muscle injuries in football. A documentary search was conducted in December 2022 from three databases: Medline via its PubMed interface, Google Scholar, and COCHRANE databases, through the following documentary request: Which exercises are effective in MI in professional football players?

The MESH terms used were prevention, muscle, injury, wounds and injury, soccer, and exercise.

The combinations of these different keywords generated the following search equation:

“Prevention” OR “Prévention” AND “muscle” AND “Wounds and injury” OR “plaies et blessures” AND “Exercise” OR “Exercice” AND “Football” OR “SOCCER”

The research question was methodically put in the PICO format to identify appropriate keywords. After exploring the digital databases, we studied the bibliographical references of relevant articles.

We included an independent double lecture of the title/abstract and full texts by two trained specialists in rehabilitation and physiotherapy (R. M) and preventive and health public medicine (D. CH), and studies on the preventive effect of program or exercise on MI.

Results

A total of 214 articles, with 112 articles from Medline, 31 articles from GOOGLE SCHOLAR, and 71 articles from the Cochrane library, were initially identified. Of these, 42 duplicates were excluded. The remaining 172 articles were screened against the eligibility criteria by title and abstract to exclude those clearly not relevant to the review topic. Following this, the full texts of 59 articles of potential relevance were retrieved, and 39 were excluded based on the eligibility criteria. Once the screening and selection processes were complete, seven articles were eligible for inclusion in the present systematic review. ( Figure 1)

Figure 1. PRISMA flowchart of the study.

Discussion

Despite the existence of multiple effective programs, teams still lack standardization in terms of MI prevention programs. This review aimed to identify the most effective programs for the prevention of MI in football. From a global view, structured programs reduce the MI rate, but more significantly, its severity and time loss to injury.

Previously, many reviews were interested in either evaluating the efficacy of one particular program¹⁰ or the efficacy of programs on one particular group of muscles.^21–22 In the hamstrings review,²¹ there was not a sufficient number of participants included in the studies (less than 20), and only the study by Whalan et al., which was included in our review, included more than 30 participants.

FIFA 11+ is the most commonly used MI prevention program.^15–18 FIFA 11+ is a comprehensive warm-up program aimed at improving muscular strength, body kinesthetic awareness, and neuromuscular control during static and dynamic movements. This program consists of three parts, 15 different exercises with a focus on neuromuscular effects on the lower extremities and core. The first and third parts include running exercises; it begins “at slow speed combined with active stretching and trolled partner contacts” and finishes “at moderate/high speed combined with planting/cutting movements”. These parts include the dynamic actions and accelerations. Part 2 consisted of six strength, plyometric, and balance exercises with a focus on core and leg strength, proprioception, and stability. Three variation levels were provided for each exercise. The 11+ program was designed to be delivered as a 20-25 min “warm-up” before commencing other training activities, without the need for specialized equipment.⁹ Its effectiveness has not been fully documented in the literature; Steffen et al., in 2013, reported an overall significant injury reduction of 72% based on secondary data analysis.²³

There were only significant differences in the study by Hammes et al.¹⁵ in terms of IR between the IG and CG. In the other studies included, FIFA 11+ did not show a reduction in IR, but there was a significant difference in terms of the severity of injury.

All players in the included studies were male, but FIFA 11+ was tested several times in female soccer players^24–25; however, the number of participants was not enough to conclude efficacy.

In the study of Mckey et al,²⁶ authors evaluated the impact of high versus low application of FIFA 11+ and found significant difference in the study of High application of FIFA 11+ but the number of participants was few “23 females” to consider those findings.²⁶

From the seven studies included, Whalan et al.¹⁸ used a particular control within group; for IG, they applied classic FIFA 11+ described above, and for CG, they proposed parts 1 and 3 before training and part 2 after training. However, significantly fewer severe injuries and days lost to injury were observed in the “P2 post” group in this study. The authors explain these findings by better compliance and adherence in the P2 post-training group, which provides a simple and practical method to potentially improve the effectiveness of the 11+ program and compliance with the 11+ program.¹⁸

Indeed, implementation of FIFA 11+ was initially difficult, and there was a lot of resistance to adherence from both coaches and players.^11,23,25,26 Many authors have studied the factors influencing adherence to the FIFA 11+ program and identified barriers to its implementation, such as program duration and exercise difficulty/fatigue. They have also shown that this adherence may be related not only to the effectiveness of the program itself, but also to beliefs and practice in football coaches’ attitudes.²⁶

In addition to FIFA 11+, Vand de Hoef used a complete bounding exercise programme. Players perform a gradual build-up of walking lunges, tripling and drop lunges, and bounding (alternating leg jumps).¹⁹

After a period of 12 weeks of buildup, players will continue BEP for the rest of the season, two sessions a week. The first gradual build-up should improve functional movement patterns and increase strength.²⁷

The bounding exercise, in the literature referred to ‘a running bound’ or ‘alternate leg bounding’, is a popular running-specific exercise that can be categorized as plyometric exercise. These plyometric exercises consist of three phases: eccentric pre-stretch, amortization phase (time between eccentric and concentric contractions), and concentric shortening phase.²⁸

Other studies focused only on a group of muscles. For example, Hasebe et al. studied the effectiveness of NHE on hamstring injury (HI).²⁰ The athletes were asked to use their arms and hands to buffer the fall, let their chest touch the surface, and return immediately to the starting position by pushing with their hands to minimize loading in the concentric phase. In this study, Hasebe et al. showed that NHE might not significantly reduce IR; however, it significantly reduced the time lost to sports due to injury (p=001).

According to literature, HI is the most frequent MI and injury in soccer. In 2001, Mjolsnes introduced the NHE, presented as an exercise that can easily be performed on pitch without special equipment, and in a randomized controlled study, the NHE group presented a 57% lower HSI (Hamstring Injury).²⁹

In addition, in a recent systematic review and meta-analysis of six studies, BIZ et al. concluded that both NHE and FIFA11+ are efficient for HSI.²¹

In the study by Azuma and Someya,¹⁴ the beneficial effect of stretching intervention was particularly strong for severe injuries that require a long time to return to play. Stretching is regularly included in warm-up exercises. However, some authors have reported the opposite finding for stretching.^30,31 The effects of stretching on MI depend on the type of sport. In sports with a high stretch-shortening cycle, such as football, when a compliant muscle-tendon unit is contracted, most of the energy is absorbed by the tendon and then MI is reduced. However, in other types of sports with low or no stretch-shortening cycles, such as cycling, most athletes are used to stiff tendons, and stretching will ll not directly cause MI. In fact, having a more compliant tendon makes them less adapted to their sports activities, so they develop more injuries.^30,32

Therefore, we can conclude that stretching is recommended for MI in soccer.

We did not include studies that used a specific program for adductors, which are frequently injured in football, because they did not meet our inclusion criteria. Most of the studies used the Copenhagen adduction exercise (CA).^33–35 It is a partner exercise. The player lies on the side with one forearm supporting him on the floor and the other arm placed along the body. The upper leg is held at approximately the hip height of the partner, who holds the leg using one arm and supports the knee with the other. The player then raises his or her body from the field, and adducts the lower leg so that the feet touch each other, and the body is in a straight line. The body was then lowered halfway to the ground while the foot of the lower leg was lowered so that it touched the floor without being used for support. This exercise was performed on both sides. It is an eccentric hip adductor exercise that prevents adductor injury. Haroy et al. showed that adding this type of exercise to FIFA 11+ may compensate for the lack of eccentric hip strengthening exercise.³⁵ In addition, Alonso et al.³⁴ showed that CA increased muscle thickness, which may reduce adductor injury.³⁴

As there are few players to conclude the effectiveness of this program, more studies with more players should be conducted for specific adductor prevention programs.

The most relevant point of our study was the diversity of programs used to prevent MI in soccer. Global programs, such as FIFA 11+ and BEP plyometric, provide players with hole strengthening and neuromuscular control. For these global programs, we may add muscle-specific exercises such as NHE and CA. Using structured devices is efficient in reducing IR, especially injury severity.

Finally, it goes without saying that prior to the exercise prescription, each player should have a specific evaluation and obtain an appropriately tailored program. In addition, it is important to target other risk factors, such as ethnicity and nutrition, which may explain the heterogeneity of the study findings.³⁶

Conclusion

MI is the most frequent injury in football. It is responsible for long-term loss to play and the end of one’s career when it is severe. Coaches, doctors, and sports scientists have always tried to produce effective programs for MI and injury prevention in general.

In our study, we aimed to identify programs with proven efficacy in MI injury prevention. We reviewed the literature on PUBMED, COCHRANE, and GOOGLE SCHOLAR databases using PRISMA. We only included randomized controlled studies that were interested in determining the efficacy of an exercise or a complete program on reducing MI in professional and semi-professional soccer players, with more than 30 effective participants in each group.

Finally, we included seven articles published in journals of good quality according to the PEDRO scale in the last 10 years. The total number of participants was 3815 male players.

The program included FIFA 11+, BEP, stretching, and NHE. There was no significant difference in IR, but there was a significant difference in severe injury and, consequently, less time loss due to injury in the IG.

Finally, we can conclude that for MI prevention in football, we may use a completely structured program such as FIFA11+, for which we can add muscle-specific exercises such as NHE and CA exercises.