Reducing Hamstring Injuries in Football: The Nordic Hamstring Curl

Injuries in football remain a substantial challenge for both teams and individual players. The time lost through injury not only represents a significant financial burden to clubs [1], but also contributes to a marked decline in overall team performance [2]. Beyond these organisational implications, the emotional toll on players who devote their lives to the sport only to be hindered by recurring injuries is profound, often preventing them from reaching their full potential.

Muscle injuries constitute approximately one-third of all football-related injuries, with hamstring strains being the most prevalent among them [3]. Compounding this issue, hamstring injuries are notorious for their high recurrence rate [4], posing an ongoing concern for athletes and medical teams alike.

Research indicates that hamstring injuries most commonly occur during the mid-to-late swing phase of high-speed running, typically affecting the biceps femoris. However, injuries can also occur through excessive stretch, more frequently involving the semimembranosus [5]. Alarmingly, despite advancements in strength and conditioning practices and sports science, the incidence of hamstring injuries in football continues to rise [6]. A plausible explanation for this trend may be the progressive increase in running intensities over time. A longitudinal study analysing Premier League matches over a seven-year period found that both high-intensity running and total sprint distances increased annually across all playing positions, including attackers, central defenders, midfielders, full-backs, and wide midfielders [7].

In recent years, the Nordic Hamstring Curl (NHC) has gained significant attention as a potential solution for reducing hamstring injury rates. A meta-analysis demonstrated that incorporating the NHC into training programmes reduced hamstring injuries by approximately 50–70% [8]. These findings provide compelling evidence for its efficacy, which explains the widespread enthusiasm surrounding this exercise. However, to make an informed assessment of its true value, it is essential to explore how and why the NHC, along with other contributing factors, may help mitigate hamstring injury risk.

The Nordic Hamstring Curl is a supramaximal eccentric exercise in which the athlete’s hamstrings are overloaded to eccentrically control the descent of the upper body towards the ground [8].

There are several proposed explanations for the consistently positive research outcomes associated with the NHC. The most widely recognised adaptation is an increase in eccentric hamstring strength, which has been found to develop through regular inclusion of this exercise [8]. Studies have demonstrated that athletes with lower eccentric strength are more likely to sustain hamstring injuries [9]. This is logical, given that the hamstrings undergo substantial eccentric loading during the swing phase of sprinting [10]. Consequently, players must possess adequate eccentric strength to tolerate the mechanical demands associated with their sprint velocities. Eccentric training therefore appears to be a valuable method for equipping the hamstrings to withstand maximal forces [11].

Moreover, the eccentric strength gains elicited by the NHC predominantly target the biceps femoris [12]— the muscle most frequently injured in football [5]. Nordic training has also been shown to induce beneficial adaptations in muscle architecture, such as increased fascicle length and greater pennation angle [13]. This is particularly significant as shorter fascicle lengths have been associated with an elevated risk of hamstring injury [14].

The effectiveness of the Nordic Hamstring Curl largely stems from its capacity to expose athletes to substantial eccentric overload. Most studies investigating eccentric overload training of the hamstrings have focused on this exercise, likely because it is both practical and equipment-free through requiring only a partner or a simple anchoring device. Nevertheless, it would be unreasonable to assume that the NHC is the only exercise capable of producing these adaptations. Provided that joint angles and relative intensities are matched, alternative exercises could elicit similar benefits. For example, emerging research suggests that flywheel eccentric leg curls can produce comparable neuromuscular adaptations [15].

It is worth acknowledging, however, that the supramaximal nature of the NHC can pose challenges for some athletes, particularly as they struggle to control their body weight when nearing full knee extension. Given that hamstring injuries frequently occur during the late swing phase of sprinting [5], it may be critical to ensure that eccentric contractions are performed at joint angles replicating those in which injuries typically occur [16]. Maintaining eccentric control at these extended knee angles is likely crucial for activating the biceps femoris and improving resilience under high mechanical stress [12]. In this context, exercises such as the eccentric leg curl may offer a more controlled means of training athletes who cannot perform the full range of motion in the NHC, while also allowing for independent loading of each limb and minimizing compensatory lumbar extension that can arise when athletes struggle with the exercise. Similarly, isometric exercises at long muscle lengths have demonstrated comparable architectural adaptations to eccentric training without the eccentric loading [17].

To fully understand the value of the NHC, it is also necessary to consider other mechanisms contributing to hamstring injuries. Interestingly, sprinting itself has been shown to produce even greater hamstring activation than the NHC [18] and can elicit equal or superior improvements in muscle architecture [19]. Sprinting also offers unmatched specificity with respect to contraction velocity and rate of force development. While developing maximal strength through eccentric training is important, athletes must also be prepared to tolerate eccentric forces at high contraction speeds [20]. Research indicates that exposure to sprinting at 95% of maximum velocity once or twice per week can significantly reduce hamstring injury incidence [20].

Establishing an appropriate chronic workload of sprinting is essential to ensure that athletes can tolerate high-speed running without excessive breakdown [21]. Conversely, excessive workload or spikes in acute workload and/or inadequate recovery may increase injury risk by impairing neuromuscular coordination [22]. Therefore, careful monitoring of sprint volume, intensity, and load management is paramount for effective injury prevention.

Strength training approaches beyond the NHC should also be considered. Although emphasis is often placed on knee flexor strength, weakness in the hip extensors may cause the hamstrings to compensate, predisposing them to injury [23]. Additionally, hip extension exercises have been shown to produce different patterns of hamstring activation compared to knee-dominant exercises [24]. Biomechanical factors may also contribute to injury susceptibility; for instance, lateral trunk flexion and anterior pelvic tilt can increase hamstring length and strain [25]. As a result, training to improve lumbopelvic control has become an important consideration for many athletes [26].

To conclude, Hamstring injuries represent both a complex and multifactorial problem within football. While the Nordic Hamstring Curl and other exercises that provide similar eccentric overload can play a pivotal role in reducing injury risk, it is clear that this exercise alone is not a universal solution. A holistic, multifaceted approach is required, incorporating controlled eccentric overload training, sprint load management, and strength development across both the hip and knee. Programmes should also be tailored to individual athlete needs and strength levels, whilst addressing specific biomechanical or stability deficits where necessary. Through such a comprehensive strategy, the prevalence of hamstring injuries in football may be more effectively reduced.

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