Will Strathdee

The hamstring musculature plays a fundamental role in athletic performance, contributing to sprint acceleration, change-of-direction capability, and injury resilience. Given the high incidence of hamstring strain injuries (HSIs) in sport, particularly among field and track athletes, strength and conditioning research has increasingly focused on refining training methodologies to enhance muscular function and mitigate injury risk.

Over the past five years, several studies have examined the efficacy of different hamstring strengthening exercises, particularly eccentric modalities, in improving muscle activation, hypertrophy, and robustness against strain injuries. This review critically analyses contemporary findings, comparing Nordic hamstring curls (NHCs) and lengthened-state eccentric training (LSET)—such as seated hamstring curls—and explores their implications for programme design in both performance enhancement and injury prevention.

The Role of Eccentric Loading in Hamstring Development

Eccentric training, wherein the muscle lengthens while under tension, has been extensively documented as a key mechanism in both injury prevention and neuromuscular adaptation. The hamstrings, which function eccentrically during the terminal swing phase of sprinting, are particularly susceptible to injury due to the high mechanical demands placed on them at long muscle lengths.

Two primary forms of eccentric hamstring training have been scrutinised in recent literature:

1. The Nordic Hamstring Curl (NHC): A closed-chain, bodyweight exercise that elicits high levels of neuromuscular activation.

2. Lengthened-State Eccentric Training (LSET): Exercises performed at extended muscle lengths, such as seated hamstring curls, which target hypertrophic adaptations more effectively.

Neuromuscular Activation: A Comparison of Nordics and Seated Hamstring Curls

A 2021 study in the International Journal of Environmental Research and Public Health investigated the activation levels of the biceps femoris long head (BFlh) across various hamstring exercises. The findings demonstrated that:

• The NHC elicited the highest activation levels, reaching 128.1% of maximal voluntary isometric contraction (MVIC).

• Seated hamstring curls, by contrast, produced moderate levels of activation, averaging 48.78% of MVIC.

This suggests that NHCs are markedly superior in maximising neuromuscular engagement, particularly in the biceps femoris—the most frequently injured hamstring muscle in sprinting and multidirectional sports. Given that reduced neuromuscular activation has been linked to increased susceptibility to strain injuries, this underscores the importance of including NHCs in an athlete’s training programme.

Muscle Hypertrophy: Are Lengthened-State Exercises More Effective?

While neuromuscular activation is crucial, hypertrophic adaptations are equally significant for enhancing force production and mechanical resilience. A 2024 study by Maeo et al. compared the effects of Nordic Hamstring Training (NHT) and Lengthened-State Eccentric Training (LSET) on hamstring muscle growth. Key findings included:

• LSET exercises, such as seated hamstring curls, resulted in superior hypertrophic adaptations in the biceps femoris long head compared to NHCs.

• Training at extended muscle lengths produced greater increases in cross-sectional area, suggesting enhanced mechanical adaptation.

These findings corroborate the broader literature on muscle hypertrophy at extended lengths, which posits that exercises performed at greater ranges of motion induce superior muscle growth and fascicle length adaptations(Schoenfeld, 2020). This has substantial implications for sprint and power athletes, as increased muscle cross-sectional area is associated with greater force output and reduced susceptibility to strain injuries.

Hamstring Strength and Injury Prevention

Eccentric Training and Injury Mitigation

A meta-analysis published in the European Journal of Sport Science assessed the efficacy of various hamstring-strengthening protocols in injury prevention. The analysis found that:

• Eccentric exercises, particularly Nordic hamstring curls, reduced hamstring strain injury incidence by 51–67%.

• Athletes engaging in consistent Nordic training exhibited lower reinjury rates, highlighting the long-term protective effect of eccentric loading.

This aligns with research by Van Dyk et al. (2019), which demonstrated that Nordic training enhances both eccentric strength and fascicle length—two primary determinants of injury resilience.

However, while NHCs have been shown to be highly effective, they should not be viewed as a panacea. Emerging evidence suggests that a combined approach, integrating both Nordics and lengthened-state exercises, offers the most comprehensive protection against HSIs.

Rehabilitation and Reconditioning Strategies

For athletes rehabilitating from hamstring injuries, research indicates that a periodised, multi-modal approach is optimal. A 2023 study in the International Journal of Sports Medicine examined rehabilitation protocols in elite athletes and reported that:

• A combination of eccentric and isometric loading led to the most effective return-to-play outcomes.

• Lengthened-state exercises (e.g., seated hamstring curls) were particularly effective in restoring atrophied muscle tissue, whereas Nordic exercises were superior for rebuilding strength and fascicle length.

• Athletes who incorporated unilateral exercises (e.g., single-leg Romanian deadlifts) improved limb symmetry, reducing compensatory imbalances post-recovery.

These findings reinforce the necessity of individualised rehabilitation programming, ensuring that interventions address both the specific deficits caused by injury and the broader biomechanical demands of the sport.

Practical Applications for Coaches and Athletes

Drawing upon the latest research, the following framework provides an evidence-based approach to optimising hamstring strength training:

1. Prioritise Eccentric Training for Injury Prevention

• Primary exercise: Nordic Hamstring Curls (2–3 times per week).

• Objective: Develop eccentric strength and increase fascicle length to mitigate injury risk.

• Best suited for: Sprint athletes, field sport players, and high-speed movers.

2. Incorporate Lengthened-State Training for Hypertrophy

• Primary exercise: Seated Hamstring Curls (slow eccentrics, full range of motion).

• Objective: Induce superior hypertrophy and architectural adaptations.

• Best suited for: Strength and power athletes, rehabilitation settings.

3. Employ a Multi-Faceted Approach for Comprehensive Development

• Eccentric exercises: Nordics, Romanian deadlifts.

• Lengthened-state exercises: Seated hamstring curls, good mornings.

• Isometric exercises: Hamstring bridge holds, Spanish squats.

• Sprint mechanics drills: To integrate hamstring strength into sport-specific movement patterns.

By employing a hybridised training model, athletes can maximise muscular development, optimise performance, and reduce the risk of hamstring strain injuries.

Conclusion

Recent research underscores the critical role of eccentric loading in hamstring development and injury prevention. While Nordic hamstring curls remain the gold standard for enhancing neuromuscular activation and fascicle length, lengthened-state exercises such as seated hamstring curls have been demonstrated to induce superior hypertrophic adaptations.

Consequently, the most effective approach to hamstring strength training is not an either/or choice between Nordics and lengthened-state training, but rather a synthesis of both. By integrating eccentric, isometric, and lengthened-state exercises, strength and conditioning professionals can design robust, research-informed programmes that optimise athletic performance while minimising injury risk.