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It’s Time That We Had A Serious Conversation About Injuries

The fourth edition of global insurance group Howden’s ‘Men’s European Football Injury Index’ has been published, and the results are staggering. The report charts a continued upward trend in recorded injuries in the Premier League, Bundesliga, LaLiga, Ligue 1 and Serie A, with a combined 4,123 injuries during the 2023-24 season representing a 4% increase on the previous season (10). The financial burden of these injuries is substantial, with the total cost for the 2023-24 season calculated at €732.02 million, a 5% rise on the year before (10). These figures are not an isolated blip, instead they highlight an alarming ongoing injury trend. Over the four seasons that Howdens have produced their report, clubs within the top five men’s European leagues have suffered a total of 14,292 injuries, with the economic impact to these teams coming in at an eyewatering €2.3 billion (10). Incredibly, last season there were 37% more injuries compared to 2020-21.

The effects of this growing injury burden are felt not only on the balance sheet, but also on the field of play. Multiple studies have indicated that teams ranked with the fewest injuries have a greater likelihood of finishing in a higher league position (9,13), a view reinforced by Howdens data on the Bundesliga. Their report revealed that during last season’s campaign, Bundesliga powerhouse Bayern Munich suffered 96 injuries, costing them not only €39 million but also, possibly, the title that they had held for the previous 11 years. Champions Bayer Leverkusen, meanwhile, sustained only 36 injuries (costing only €3.45 million) as they won the Bundesliga by 12 points (10).

Is Our Injury Screening Process Fit For Purpose?

This highlights a crucial point. Teams know that increased player availability improves both team effectiveness and the probability of winning games, making injury reduction one of the main prerequisites for success. For this reason, clubs are allocating ever greater resources to turn the tide on injuries. Significant investment has been made to expand Sports Medicine and Performance Departments, equipping them with the expert staff and latest technologies needed to deliver effective injury mitigation strategies, particularly in crucial areas such as player screening, testing and monitoring. Never before has so much effort been made to reduce injuries – yet never before have injuries been so prevalent. So, we have to ask ourselves some serious questions: Are we going about this the wrong way? Do the screening tools we presently use truly give us valid and reliable data concerning a player’s risk of sustaining an injury? Is our testing sensitive enough to give us the information we need to create effective injury reduction protocols for each individual player? Are our monitoring systems really having any real impact?

To Reduce Injuries We Have To Adopt A Multi-faceted & Individualized Approach

One important consideration we must be careful not to overlook is that injuries can be influenced by a number of different intrinsic and extrinsic factors. These can include, but are not limited to: the injury history of the player, the players age, neuromuscular control, individual fitness levels, team tactics and style of play, playing position, the content of the players strength & conditioning program, team playing and training schedules, travel, the implementation of appropriate recovery strategies, the quality of the players nutrition, and, crucially, the lifestyle choices which are made by the players themselves. The individualized nature of player responses means that different combinations of these factors are likely to affect different players in different ways, therefore if we only rely on one or two screening tools in isolation, we probably won’t be seeing the complete picture. In other words, to minimize injury occurrence as effectively as possible, it is vital that we adopt a multifaceted, integrated and highly customized approach which takes into consideration the unique characteristics of each player. Reducing injuries requires a bespoke and individualized focus rather than a ‘one size fits all’ approach, therefore we should be striving to create specialized management strategies which are tailor made for each player. To achieve this, we may have to broaden our perspective and think about injury risk factors from a different angle. Let’s consider what this might look like by looking at the one injury that stands above the rest – hamstring strains.

We’ve Always Known That Hamstrings Are An Issue – So Why Is The Problem Getting Worse?

The stats surrounding hamstring injuries in soccer are astounding. Hamstring injuries in the men’s professional game have doubled in 21 years, and now represent 24% of all soccer injuries (7). A playing squad will average 8 hamstring strains per season, and, every year, 20% of players will miss training or match play due to hamstring injury, with the average lay off for a player following a hamstring injury being 13 days. The risk of re-injury is high; players with a history of just one previous hamstring injury are 2.7 times more likely to sustain an injury than players with no hamstring injury record (7) – and this risk increases with any subsequent injuries. 18% of all hamstring injuries are recurrences, the vast majority of which are classified as ‘early recurrences’, meaning they happen within two months of the player returning to play.

Clearly, professional soccer teams have a strong incentive to address this epidemic of hamstring injuries, and as a result are devoting ever more resources to solving the problem, but are they looking in the right place? Do their screening tools and monitoring systems identify what causes a hamstring to fail in the high intensity environment of a soccer game, or only under the carefully controlled conditions of the training centre? The stats would suggest that something is being missed, so, is our player screening process truly taking into account how and why hamstring injuries occur under functional loading conditions, or in reality, is our testing largely non-functional? To expand upon this question, here we look at 10 identified risk factors for hamstring injury.

10 Injury Risk Factors For Hamstring Strains

1. Previous Hamstring Injury

The most significant risk factor for hamstring injuries is previous hamstring injury. Players with a history of hamstring strains are 2-6 times more likely to suffer a subsequent injury, with the highest risk coming in the first 8 weeks following return to play (3). This is a matter of concern, because re-injuries have been shown to cause significantly longer player absences than initial injuries. Two important questions are raised by this finding:

– Firstly, are re-injuries being contributed to by ineffective injury management, inadequate rehabilitation or poor-quality return to play programmes for these injured players?

– Or, secondly, has the original injury caused a maladaptation or a change in muscle function which will affect the long-term health of the player, meaning that they will have to be managed in a different way in their future training programmes? Studies have shown that injury can result in both eccentric weakness and atrophy of the long head of the biceps femoris (BF) – the muscle where 84% of hamstring injuries occur (6). Evidence suggests that previously injured BF long head muscles present significantly shorter fascicles than muscles without history of injury (14). We know that the hamstring has to be strong eccentrically to withstand the forces generated during the terminal swing phase of high-speed running – this has been identified as being the point when the majority of hamstring injuries happen. The combined effects of eccentric weakness, BF atrophy and shorter fascicle length associated with previous injury could lead to an increased risk of players suffering an injury recurrence.

What this means
Players who have a record of hamstring injuries should incorporate both eccentric exercises and exercises which preferentially recruit the long head of the BF into their training programme to restore muscle architecture and reduce the likelihood of reinjury.

2. Age

The second injury risk factor is age – players appear to be more susceptible to hamstring injury as they get older. This may be due to age-related loss of muscle mass, or to changes in muscle structure leading to decreased strength (1).

What this means
The risk associated with increased age can be mitigated by improvements in eccentric strength (15). This means that older players need to devote more training time to hamstring injury reduction protocols, in order to ensure that they remain healthy and injury free.

3. Hamstring Strength

The strength capacity of the hamstring muscle itself plays a huge role in the ability of a player to avoid injury. Poor hamstring strength means that the forces being generated while sprinting are likely to exceed the tolerance of the muscle-tendon unit of a weak hamstring, causing it to fail. Studies have demonstrated that athletes with lower eccentric hamstring strength have over 4 times greater risk of a hamstring injury than stronger players (2).

What this means
A key strategy to prevent hamstring strains is to increase the strength capacity of the muscle, thereby raising the safety threshold for injury. This requires two important factors to be addressed:
– Firstly, it is vital that the player’s FUNCTIONAL eccentric hamstring strength is regularly monitored and assessed. Functional means that testing must assess the way that the hamstring operates while sprinting, specifically during the late swing phase when the hip is flexed and the knee is extended. However, the majority of eccentric strength screening uses a measurement tool based on the Nordic curl, which prioritises the knee flexors whilst the hip remains relatively extended. This raises an important question about the validity of testing.
– Secondly, exercises which strengthen the muscles of the hamstring, specifically in the way that it functions during sprint actions, should be incorporated into each players weekly programme. In this context, eccentric hamstring strength training has been shown to reduce the risk of hamstring strains by 65%-85% (4).

4. Neuromuscular Control: Intermuscular Co-ordination

Neuromuscular control can have a considerable influence on hamstring injury risk. Firstly, in terms of intermuscular co-ordination, the muscles in the posterior chain must function effectively to prevent the hamstrings from becoming overloaded. The gluteal and the lumbar erector muscles are responsible for the safe and effective transfer of forces in the body, acting synergistically with the hamstrings. If during a sprint there is a delay in the onset of hamstring activity, and a primary activation of the lower back muscles, there will be an increased risk of hamstring injury.

What this means
Players should be exposed to exercises of progressively increasing complexity and challenge, designed to improve neuromuscular control and reinforce appropriate firing patterns in the posterior chain.

5. Neuromuscular Control: Intramuscular Co-ordination

The muscles in the hamstring, particularly the biceps femoris (BF) and the semitendonosus (ST), must work in a specific and synchronised neuromuscular pattern when an athlete is sprinting. In a well-functioning hamstring, the BF is activated just before and immediately after the foot hits the ground, whereas the ST is activated during mid and late front swing – and this is the point where the majority of hamstring injuries occur. The ST is more prone to premature fatigue – and when it tires, this lack of ST activation is compensated for by the BF, which then becomes overloaded. What is important about this is the fact that the BF is not suited for force production in the distal range of motion (mid to late front swing, where the ST is normally active), and when it starts doing the job of the ST, this puts it at risk of injury (16).

This reflects two of the facts that we know about hamstring injuries. Firstly, that they occur more frequently when players are fatigued, and secondly that the majority of injuries occur in the BF. For that reason, a functionally balanced BF-ST unit is of major importance to hamstring injury reduction.

What this means
In order to protect the BF, practitioners should pay attention to the function of the ST – specifically its ability to withstand fatigue.

6. Lumbopelvic Hip Stability: Running Mechanics

The pelvis is responsible for force transfer between the lower limbs and the spine – and any dysfunction in the way that it performs this task during high speed running can increase risk to the hamstrings. Specifically, an athlete sprinting with an excessive forward lean of the trunk creates an anterior pelvic tilt. This anterior tilt of the pelvis elongates the hamstring and causes it to stretch, creating tension and strain. When an already stretched, hamstring is then exposed to the additional force generated during a sprint, the risk of it failing increases (5).

What this means
Practitioners must screen players to ensure that they are moving well with good, efficient sprint mechanics which minimise forward trunk lean. The issue of anterior pelvic tilt is closely related to….

7. Lumbopelvic Hip Stability: Core Strength & Proximal Control

Anterior pelvic tilt is caused by poor activation and inadequate control of the core. The core muscles are used to modify the tilt of the pelvis during running, which in turn influences the length of the hamstring and the resulting injury risk to the hamstrings (5). For that reason, the levels of core strength and proximal control that the player has is a significant injury risk factor.

What this means
Players should adopt core strengthening exercises which train the trunk under functional loading conditions. Functional loading means that the player has to maintain a neutral pelvis position whilst replicating the two functions performed by the hamstrings when sprinting – hip extension and knee flexion.

8. Work Capacity & Fatigue Tolerance

Player fitness can be considered as being a risk factor for hamstring injury. In soccer it has been identified that hamstring injuries occur more frequently towards the end of each half, when players are tired. Acute fatigue causes the muscles of the hamstring to function in a less coordinated manner (11), reduces eccentric hamstring strength (5) and increases anterior pelvic tilt (11), all factors which increase the risk of injury. Across all sports, players with elevated physical abilities are more resilient to injury.

What this means
Practitioners should ensure that players develop high levels of physical capacity in order to cope with the demands of their sport. This will enable them to resist fatigue and protect against potential injury.

9. Playing Position & Style of Play

Playing position can also influence the potential for hamstring injuries. Certain positions have greater sprint demands than others, which results in an increased load on the hamstrings – and we know that most hamstring injuries occur during sprinting. For example, in the NFL the majority of hamstring injuries occur in the defensive back (23%) and wide receiver (21%) positions, where sprint demands are highest (12).

What this means
It is particularly important that all athletes who play in positions with a high sprint component engage in hamstring injury reduction training – and this is true of any sport. Placing a high priority on hamstring specific protocols will ensure that players are capable of coping with the physical demands imposed by their position, and will have a better likelihood of avoiding injury.

10. Change to Training Programme

Athletes become adapted to a particular way of training, and unexpected changes to their normal, established routine can increase the risk of injury. Studies in elite soccer have shown that changing coaching staff mid-season can lead to 3 times increase in hamstring injury (8), with the sudden adjustment to playing and training philosophy accompanied by a rise in the number of injured players. Excessive and rapid increases in physical loads, particularly sudden spikes in high speed running, are responsible for a large proportion of hamstring injuries.

Conversely, reducing training load can also lead to an increased risk of injury in games, because under-trained players are not adequately prepared to cope with the greater physical demands they experience during match play.

What this means
Both over-training and under-training can increase hamstring injury risk, therefore achieving a balanced and optimal training load is a crucial factor for injury reduction. This means that monitoring load is an essential part of the overall injury reduction process.

What this all means

To prevent injuries, we have to understand why they happen – this will then allow us to develop interventions which are designed to mitigate those risks. We have seen that hamstring injuries can be influenced by a number of different intrinsic and extrinsic factors, such as injury history, age, neuromuscular control, lumbopelvic hip stability, fitness levels and playing position. Professional teams regularly collect player specific data in a bid to reduce hamstring injuries, most commonly in the form of eccentric or isometric strength testing, functional movement screening and monitoring training outputs using GPS technology. However, if they rely on only one or two of these screening tools in isolation, they probably won’t be seeing the complete picture. For that reason, to minimise the incidence of injury as effectively as possible, it is vital that we adopt player screening and monitoring protocols which are capable of accommodating numerous identified injury risk factors as part of a multi-faceted, integrated approach. Every staff member who is involved with player preparation – the medical professionals, the sports science department, the coaching staff, and, crucially, the athlete themselves – has a role to play in reducing injuries. To achieve this level of cross-departmental collaboration, the flow of information and data relevant to injury mitigation is vital.

Where Apollo Makes A Real Difference

Apollo’s athlete performance software unlocks data silos allowing coaches, trainers, doctors and players to become masters of data-driven performance with real-time data visualization and collaboration tools. Our software is integrated with over 80 performance focused technologies used by college and professional athletes. With Apollo, teams have the information they need to minimize hamstring injuries and optimize player availability.

To learn more about using Apollo for injury reduction, email info@apollov2.com.

Written by Adrian Lamb, ApolloV2 Sports Scientist

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WHAT APOLLO CAN DO FOR YOU

ApolloV2 is not a traditional ‘one size fits all’ athlete management system. Instead, we are a highly adaptable platform which can create customized dashboards specifically tailored to each team’s individual needs and unique way of working.

Our system equips teams with the ability to generate custom-made data visualizations without software code. We have more API’s than any other system, which allows us to collect data from the multiple tools and systems staff are using, and then combine it efficiently to allow coaches to make informed decisions with their players.

We have Power Bi and Tableau integrated into our ecosystem, which enables us to build bespoke, best-in-class data reports designed to meet specific requirements and ensure that coaches receive the data driven insights they need, to inform decision making and influence positive change.

To learn more about using ApolloV2 for performance enhancement, email – alamb@apollov2.com.