Hamstrings muscle architecture and morphology following 6 weeks of an eccentrically-biased romanian deadlift or Nordic hamstring exercise intervention

Key Points

1. The Romanian Deadlift is an exercise that can elicit the same desirable architectural changes in the hamstring musculature as the Nordic Hamstring Exercise.
2. A period of two weeks detraining is sufficient to reverse a number of these changes back to baseline pre-intervention levels.
3. Regional changes in musculature is more related to the individual performing the exercise than the exercise that they are performing.

BACKGROUND AND OBJECTIVE

It is well published that hamstring injuries pose a large problem to both athletes and the medical teams working with them. One method of addressing this troublesome injury is the well-researched Nordic Hamstring Exercise which is known to positively influence two modifiable risk factors to hamstring injury.

The exercise both increases fascicle length and decreases pennation angle within the Biceps Femoris Long Head (BFlh), which has been shown to substantially decrease the risk of injury in the posterior thigh (1).

Despite this well-known link between the ability to address risk factors there is some apprehension in administration of this exercise, both from athletes who associate the exercise with high levels of delayed-onset muscle soreness (2), and from practitioners who do not believe that prescribing an exercise with neutral hip position for a bi-articular muscle is appropriate.

This paper’s main objective was to understand the differences in regional BFlh architecture and morphology with a 6-week intervention utilizing either the Romanian Deadlift (RDL) or the Nordic Hamstring Exercise (NHE).

Hamstring injuries pose a large problem to both athletes and the medical teams working with them.

If we are to continually challenge and stimulate our athletes, the variety within programming is key, and this paper assists with this decision-making around prescription and programming.

METHODS

• A total of 32 participants of whom 17 were male, were recruited to the study. These participants were all between the ages of 18 and 25 and had no history of hamstring injury within the past six months. The participants were randomly allocated to one of the two intervention groups.

• The study was completed over a six-week intervention period whereby subjects underwent two supervised training sessions per week according to their allocation. The initial two weeks were deemed a familiarization period to allow the participants to complete four sets of four repetitions of their allocated exercise at a targeted intensity of 8-9/10 through addition of external weight. In the case of the RDL, weight was added to the barbell, and with the NHE a weight plate was held across the chest with loads increased by 2.5kg to maintain the desired rate of perceived exertion (RPE). For video demonstration, see video 1.

VIDEO 1 - NHE AND RDL EXERCISE

• The duration of the eccentric contraction was also controlled within the protocol, with the first week being four seconds, five seconds in the second week and the final four weeks being six seconds in duration. This lower body exercise was completed alongside a standardized whole-body program.

• Following completion of the six-week program there was a two-week period of detraining, following which all outcome measures were re-assessed.

RESULTS

• Good compliance was present throughout both groups, with the RDL and NHE groups achieving 95% and 94% respectively.

• Fascicle length was monitored at the three time points and in both intervention groups there was a significant increase in Biceps Femoris Long Head fascicle length from the period of baseline to post-intervention. There was then a subsequent decrease as a result of the detraining period. This was the same pattern seen within pennation angle, whereby a desirable decrease in pennation angle was achieved as a result of both interventions, but as with fascicle length, this was subsequently reversed as a result of the detraining period.

• Anatomical cross-sectional area of the hamstring musculature was also seen as a result of both interventions, with a drop off seen as a result of detraining. This drop off did not see a return to pre-intervention levels in this specific objective marker.

LIMITATIONS

One proposed limitation of this study is that although the two exercises were matched in relation to intensity and prescription, they are not specifically matched in terms of the nature of muscle contraction. The NHE is a purely eccentric activity, whereas the RDL is only eccentrically biased in relation to the fact that the subjects had to lift the weight concentrically to get back to the start position for the exercise. This mixed contraction method may have provided less load to the RDL allocated group than the NHE group.

A further limitation of the study is highlighted by the authors as the length of time the study was completed over, with six weeks potentially not being enough to truly understand what changes can be achieved through the intervention.

CLINICAL IMPLICATIONS

This study has potentially important clinical implications and application for practitioners working within fields whereby hamstring injuries pose a big challenge. We know that the burden of these injuries is increasing within elite football (3) and so it is important that as practitioners we truly understand the potential benefits of all exercises that we look to prescribe to our patients.

This study's key strength lies in its well-structured and progressive exercise prescription, ensuring a consistent overload with an RPE of 8–9/10 after a two-week familiarization period. This approach is essential to achieve the study’s observed benefits, such as reduced pennation angle, increased fascicle length, and greater cross-sectional area.

Technical execution of the exercise, particularly the eccentric emphasis and timing in the RDL, was crucial to the study’s success. The researchers’ precise prescription of eccentric time under tension, rather than just sets and reps, likely played a key role in achieving the positive outcomes.

Another interesting aspect of this study is that the authors looked in more depth than previous studies, by assessing the regional differences within the musculature. Findings of differences in individuals rather than through training exercise further highlights the issues that we have as practitioners in ensuring our patients are being provided with the correct intervention. As this study demonstrates, due to unique muscle architecture and make up, some subjects will have different adaptations to the same stimulus.

The final take away from this study is just how quickly all of the physiological adaptations were reversed following a period of detraining. The authors demonstrated that improvements in fascicle length and pennation angle from a six-week intervention were essentially lost in as little as two weeks detraining.

This again highlights the benefit of demonstrating the RDL as an equally beneficial tool in eliciting hamstring architectural change. If we are to continually challenge and stimulate our athletes, the variety within programming is key, and this paper assists with this decision-making around prescription and programming.

+STUDY REFERENCE

Crawford S, Sandberg C, Vlisides J, Thompson Q, Mosiman S, Heidersheit B, Hickey J (2025). Hamstrings Muscle Architecture and Morphology Following 6 Weeks of an Eccentrically-Biased Romanian Deadlift or Nordic Hamstring Exercise Intervention. Medicine & Science in Sports and Exercise, Epub ahead of print.

SUPPORTING REFERENCE

1. Timmins, R.G., Bourne, M.N., Shield, A.J., Williams, M.D., Lorenzen, C. & Opar, D.A. (2016). Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): A prospective cohort study. British Journal of Sports Medicine, 50, 1524-1535.
2. Chesterton, P., Tears, C., Wright, M. & Portas, M. (2020). Hamstring injury prevention practices and compliance of the Nordic hamstring program in English professional football. Translational Sports Medicine, 4(2), 214-222.
3. Ekstrand, J., Bengtsson, H., Walden, M et al. (2022). Hamstring injury rates have increased during recent seasons and now constitute 24% of all injuries in men’s professional football: the UEFA Elite Club Injury Study from 2001/02 to 2021/22. British Journal of Sports Medicine, 57(5), 292-298.