Eccentric Hamstring Training Reduces Stiffness While Building Size and Strength
New research reveals that three-times-weekly eccentric deadlifts at long muscle lengths decrease passive stiffness.
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This study investigated whether eccentric-only resistance training at long muscle lengths can reduce passive muscle stiffness in the hamstrings while simultaneously increasing strength and size—outcomes traditionally thought to be contradictory.
Thirty-six healthy young males were divided into three groups: two training groups performing eccentric-only stiff-leg deadlifts either twice-weekly (W2) or three times weekly (W3) for 10 weeks, and a control group (CON) that performed no training.
Aim
The primary aim was to determine whether eccentric-only resistance training with long muscle lengths and long contraction duration (5 seconds per repetition) at different weekly frequencies could chronically decrease passive stiffness of the biarticular hamstring muscles, specifically the semimembranosus (SM), biceps femoris long head (BFlh), and semitendinosus (ST). The hypothesis was that SM stiffness would decrease, particularly at higher training frequencies, while strength and size would increase.
Methods
Participants performed eccentric-only stiff-leg deadlifts at 50-100% of their exercise range of motion with 5-second eccentric repetitions. Training loads progressed from 60% of body mass (weeks 1-4) to 65% (weeks 5-7) to 70% (weeks 8-10). Each session consisted of 3 sets of 10 repetitions with 2-minute rest periods. Total training volume was 600 repetitions for W2 and 900 repetitions for W3.
Researchers measured passive muscle stiffness using shear wave elastography (shear modulus), maximal isometric knee flexion torque, individual hamstring muscle volumes via MRI, maximal joint range of motion, and passive torque. All measurements were taken before and after the 10-week intervention period.
Results
The W3 group experienced an 11.4% significant decrease in semimembranosus stiffness (shear modulus decreased by -13.3 kPa, 95% CI: -21.2 to -5.4 kPa), while BFlh and ST stiffness remained unchanged. The W2 group showed no significant changes in passive stiffness for any hamstring muscle. The control group also showed no changes.
Both training groups significantly increased maximal isometric knee flexion torque: W2 increased by 20.3% (17.6 Nm, 95% CI: 8.7 to 26.5 Nm) and W3 increased by 26.2% (17.4 Nm, 95% CI: 9.2 to 25.6 Nm). There was no significant difference in strength gains between the two training groups despite the higher training volume in W3.
Semimembranosus muscle volume increased significantly in both training groups: 5.7% in W2 (15.3 cm³, 95% CI: 11.9 to 18.7 cm³) and 7.4% in W3 (21.5 cm³, 95% CI: 13.3 to 29.7 cm³). W2 also showed increases in BFlh volume (8.8 cm³), while W3 did not. Whole hamstring volume increased in both W2 (29.2 cm³) and W3 (32.0 cm³) with no significant differences between groups.
Interestingly, individuals with higher baseline SM stiffness experienced greater decreases in stiffness after training (ρ = -0.733, p = 0.021). No significant changes were observed in maximal joint range of motion or passive torque in any group.
Practical Takeaways
Training three times per week with eccentric-only stiff-leg deadlifts at long muscle lengths can reduce semimembranosus stiffness while building strength and size. Use 5-second eccentric repetitions through the bottom 50-100% of your range of motion, performing 3 sets of 10 repetitions per session. Progressive loading from 60-70% body weight over 10 weeks is effective. However, twice-weekly training appears insufficient to reduce muscle stiffness, though it still increases strength and size comparably to three-weekly sessions
This training approach may be particularly beneficial for individuals with naturally stiffer hamstrings, as they demonstrated the greatest stiffness reductions. For injury prevention, especially in activities involving extreme hip flexion with knee extension (kicking, sprinting, dancing), this method could reduce hamstring strain risk by decreasing passive stiffness in the most injury-prone muscle—the semimembranosus.
Static stretching remains more effective for reducing muscle stiffness (approximately 21.5% reduction in 4 weeks versus 10.2% reduction in 10 weeks with eccentric training), but eccentric training offers the unique advantage of simultaneously building strength and size rather than potentially compromising them. This makes eccentric training a more time-efficient option for athletes and lifters seeking multiple adaptations.
Key Takeaways
This is the first study demonstrating that resistance training can chronically decrease passive muscle stiffness while simultaneously increasing muscular strength and size, challenging the conventional belief that resistance training inevitably increases stiffness. The effect is muscle-specific, with only the semimembranosus showing stiffness reductions, likely due to its shorter fascicle length resulting in greater sarcomere lengthening during the exercise. Training frequency matters critically: three weekly sessions produced stiffness reductions, while two sessions did not, despite both frequencies yielding similar strength and hypertrophy gains. The mechanism differs from traditional static stretching, instead using high-load eccentric contractions at long muscle lengths with extended time under tension. This training modality may reduce hamstring injury risk while improving performance, offering a paradigm shift from relying solely on static stretching for stiffness management.
Reference
Kawama R, Takahashi K, Ikifune H, Tozawa H, Obata T, Ito R, Hojo T, Wakahara T. Can Eccentric-Only Resistance Training Decrease Passive Muscle Stiffness While Increasing Size and Strength of Hamstrings? Med Sci Sports Exerc. 2024 Dec 1;56(12):2349-2361. doi: 10.1249/MSS.0000000000003516. Epub 2024 Jul 15. PMID: 39010311.
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