Hamstring Injuries: Understanding the Internal Ecology of Injury

A primer on the internal factors and dynamics that attract injury.

Source

Throughout time, injuries to the hamstring have perplexed those in sport performance and sports medicine. From the understanding of injury mechanisms, proper rehabilitation, and training for return to sport have constantly provided a challenge for those in the field of athlete management. We at Absolute accept that challenge and would like to provide our insight into the management of hamstring injuries.

Increasing Injury Rates

Hamstring injuries have always been a limiting biological constraint on athletes, but there has been and continues to be an uptick in these injuries. With this information, in 2021, the NFL, through their scientific advisory board, awarded a $4 million grant for a four-year study led by University of Wisconsin researcher Dr. Bryan Heiderscheit on hamstring prevention and treatment.¹ While we eagerly await the outcomes of this research, we hold reservations about its potential to achieve the advisory board's desired impact in mitigating hamstring injuries and enhancing treatment for a return to performance.

In our initial essay at Absolute, we explored the issue of stagnation in sport performance, attributing a large portion of it to the adherence to an antiquated, incomplete, and inaccurate treatment and training framework. To support and bolster our argument, we have written extensively about contemporary examples of elite athletes whose careers have been impacted due to the continued use of this outdated training and treatment paradigm.

One such example in the context of hamstring injuries is the case of Cooper Kupp of the LA Rams earlier this year. Despite having no obvious barriers to training and treatment, he was unable to report to training camp in a physical state ready to compete at a high level. Kupp is not alone in facing such challenges; even the highest-paid player in the NFL, Joe Burrow, reported to training camp not at Point B and sustained a calf injury on a non-contact, low-effort play on the first day. We highlight these cases not to rub salt in the wound but hopefully to underscore the evident issues within the current training and treatment approaches in sport and to ask deeper questions, comb the scientific evidence, and provide our insight. With this, our aim is to always educate strength practitioners on the existing problems and to learn from such examples to better prepare the athletes under their care and responsibility.

Please keep in mind that we are not solely writers (as you can probably tell); we are strength practitioners who are responsible for athletes as well. In other words, we have skin in the game.

The Traditional View

There have been significant advances in the scientific literature over the last decade regarding hamstring strain injuries and the factors associated with them. This includes everything from the mechanism of injury, predisposing factors to injury, and the architectural properties of the injured hamstring to highlight a few areas of analysis. Consequently, the hope would be that the advancement of training (including rehabilitation) would also advance; however, unfortunately, in our opinion, it hasn’t.

There are a number of reasons that specific training of the hamstrings has not advanced accordingly:

1. With a better understanding of the mechanisms of hamstring injury, rehabilitation and training has focussed simply on movements that are similar to the mechanism with no consideration of load and intensity and the influence of these in sport.

2. Solely training movement patterns that replicate the action of the hamstrings with the intent of carrying over to sport.

3. An incomplete picture of tissue-specific properties of injury and how to subsequently train for the emergent behaviours of these tissues.

4. An over-reliance on eccentrics. It is evident that eccentrics hold tremendous value in any hamstring training program; however, they must be part of a logical training progression that involves preparing the tissues for such load. The Nordic is not the unicorn to hamstring training.

5. A non-ecological framework to training. All training for hamstring strains occurs externally with no consideration of the athlete’s internal ecological niche.

6. A lack of understanding of the contribution of different sub-systems to the emergent functioning of the system (athlete) as a whole and specifically the hamstrings. It is imperative that the peripheral biological structures are linked together with the CNS (and vice versa) through various feedback mechanisms that occurs through proper training.

The Absolute View

When it comes to soft tissue injuries, including muscle strains and tears, it is our view at Absolute that we must ask more specific questions regarding the type of tissue involved and the necessary behaviour of that tissue under load. In this way, we can attempt to understand in greater detail the biological impact of the injury, as well as the eventual training parameters that should be used to allow for the necessary tissue-specific strength behaviours during performance.

In a short clip taken from one of Dr. Heiderscheit’s professional lectures, he draws attention to the connective tissue (pictured below on an MRI scan) and points out that even upon return to play, the “muscle” is not fully recovered. In another lecture, he discusses the same topic showing two different MRI scans showing a large area of fibrous scar within the proximal portion of the hamstring, and again mentions how the athlete has returned to play as a result of passing a group of clinical tests, including, no pain on palpation (non-specific), normal range of motion, the ability to sprint with no apprehension, as well as demonstrating “normal” strength on testing (doesn’t mention which tests).

Image from Dr. Brian Heiderscheit showing persistent connective tissue deficit in an athlete who has returned to play after a hamstring strain injury.

It is later revealed that the athlete did show some underlying strength deficits as demonstrated on isokinetic testing. These deficits were shown at longer muscle lengths whereby the hamstrings, by way of the CNS, were not able to generate torque, and therefore the peak torque significantly dropped at these lengthened ranges of motion.

Image from Dr. Brian Heiderscheit showing a decrease in peak torque of both limbs at long muscle lengths post hamstring strain injury.

In the literature, peak torque is a measurement of the strength and ability of a muscle to move a joint at a particular range of motion. The significance of the finding of decreased torque at longer muscle lengths in the hamstring is that it has an impact on the movement and control of the corresponding hip joint both in an open chain movement skill which occurs during hip flexion and a closed chain movement skill where the foot is planted, the hip is flexed, and the hamstring has to initially dissipate force and then generate force isometrically. Both of these scenarios happen in sport with high frequency, and both of them are significant mechanisms to hamstring injury.

The continued non-ecological management of hamstring training both after injury and for performance is a limiting factor to comprehensive and effective management of this anatomical region. This continues to be a factor in the rate of injury and re-injury for athletes.

A high-quality ecological training program (plan of management post-injury) should have the following characteristics:

1. Qualify the specific capacities necessary of the hamstring as defined by the individual’s Point B.

2. Qualify the specific training parameters to allow the acquisition of those capacities. (load, effort, and intent)

3. Be run conjugate in nature, therefore achieving multiple effects simultaneously.

It is our feeling at Absolute that all good training programs will ultimately fail in achieving their expected long term goals as a result of not having these characteristics accounted for. It will be interesting to see the continued research and results of the NFL scientific advisory on hamstring injuries.

Founders Meeting on Absolute’s View of Hamstrings Training

Be alert for a founder's meeting next week that will include a discussion on our perspective regarding Point B for the hamstrings, followed by an open dialogue and a Q&A session with the founders. We will collectively explore various training strategies aimed at reaching our defined training and treatment objectives.

1. Campbell, Dave. "The NFL is making data-driven progress on leg muscle injury prediction and prevention." AP News, September 20, 2023, URL.