Hamstring Development: Theory & Application

Hamstrings are one of the many constructs we still have yet to figure out in the sport science and sport medicine world. Athletes are still injuring their hamstrings at an alarming rate even though we have a great deal of research in the field. The purpose of this article is to break down some of the research I use to determine the reasoning and methods I use to develop robust athletes. I am not writing this article to tell you that I have the golden ticket and this methodology has prevented all hamstring injuries, but I use the literature as well as my own experiments to determine best practice. What I must preface is that this is only a model for development of the hamstrings, concepts are always being taken away or added to develop my hamstring model.

The hamstring muscles consist of 4 different muscles. Three of the four hamstring muscles cross and act upon two joints, the hip and knee, as such they are termed biarticular muscles. The semitendinosus (ST) and the semimembranosus (SM) extend the hip when the trunk is fixed; they also flex the knee and inwardly rotate the lower leg with the knee is bent. The bicep femoris consists of two muscles the biceps femoris long head (BFlh) and the biceps femoris short head (BFsh). The biceps femoris long head like the ST & SM is a biarticular muscle, its functions mostly as a hip extensor and is a weaker knee flexor compared to SM & ST. The biceps femoris short head only crosses and acts on one joint (knee) (figure 1). Now that we understand the functions let’s look at to how they are trained.

FIGURE 1.

When training the hamstring I like to break it down into three regions: proximal, distal, and integrated. The proximal portion of the hamstring is trained mainly via hip hinging movements such a Romanian deadlift, good mornings, back extension, etc. The distal portion of the hamstring is trained via knee flexion exercises such as leg curls, Nordic hamstring curl, Russian curl, etc. Lastly, the integrated portion which is the combination of distal and proximal is trained via static exercises mostly such as Alex Natera’s run specific isometric hip hold (figure 2), and back extension isometric holds to name a couple. Furthermore, the breakdown of these exercises into the regions I have stated is important because different exercises target the certain portions of the hamstrings greater than others. From an injury protection standpoint this becomes important as the goal of a practitioner is to build a robust athlete. Zebis et al. found that kettlebell swings (proximal) targeted the semitendinosus and the supine leg curl (distal) targeted the bicep femoris [19], this gives us the idea of segmenting the training of the hamstrings to elicit the greatest adaptations. 

FIGURE 2.

Hamstring strains are one of the most common injuries in speed, strength, power sports such as track and team sports [8]. The research available to us states that a muscle strain injury occurs after extreme eccentric contractions, which is why hamstring strains are likely to happen in the late swing/terminal swing phase and late stance/takeoff phase of running (figure 3) [8]. Given that we know that the hamstring injuries are common in sport we must pay attention to it and make it an important portion of our injury protection program, in Qatari professional football lower injury rates strongly correlate to team success[3], the best ability is availability. Furthermore, as a practitioner this could be the difference in being gainfully employed or not! As for the athlete hamstring muscle strains and/or previous hamstring muscle strains can leave you susceptible to a future ACL rupture [11]. Specifically the medial hamstrings have been shown to prevent excessive dynamic valgus and external rotation of the knee joint in sport [19]. Moreover, during dynamic movements such as sprinting, cutting, and decelerating a coactivation of the hamstrings is important to provide stability in the knee to prevent excessive ACL shear forces, in this case the hamstring muscles are considered ACL agonists [19]. Now there are other factors that can lead to hamstring strains such as lack of muscle length, lack of muscle flexibility, strength imbalance, warm up, fatigue, lower back injury, poor lumbar posture, and increased muscle neural tension; all factors that have been identified as modifiable risk factors, most of which are beyond the scope of this article [8].

FIGURE 3.

We discussed earlier the use of proximal, distal, and integrated exercises (figure 2). Hip hinging movements (proximal) target medial hamstrings to a greater degree than lateral hamstrings and knee flexion exercises (distal) target lateral hamstrings to a greater degree than medial hamstrings [19]. Integrated exercises are exercises that combine both proximal and integrated exercises into one exercise, for example the razor curl no return (figure 4)[10]. Putting these categories of exercises into your training program can help protect your athletes against hamstring injuries. As for volume there is research showing that high volumes of eccentric hamstring training leads to exercise induced muscle damage (EIMD) which in turn leads to delayed onset muscle soreness (DOMS) [9, 15]. DOMS is a sensation of dull, aching pain, which can be felt during palpation of the affected muscle [9], looking at the research with regards to Nordic hamstring interventions you will see reps in the 12-15 rep range. From a pragmatic standpoint it does not make sense to perform these rep ranges for reasons I alluded to earlier. There is evidence that athletes will see the same benefits using high volume (2 x 10 reps) vs. low volume (2 x 4 reps), more importantly strength gains are similar as well as muscle architectural changes are similar [12]. With that being said with any eccentric hamstring exercise I will stay in the 4-6 rep range for a few reasons: limits DOMS, strength levels will improve in the hamstrings at this rep range, muscle architectural changes will still happen, lastly I will get better quality reps out of my athletes as eccentric hamstrings exercises are already tough in of itself.

FIGURE 4.

Sprinting by definition is running as fast as possible to cover a short distance. In team sports such a rugby, soccer, and basketball sprint performance has been shown to be an important determinant of match-winning actions [1, 14]. In the German soccer league 45% of goals were preceded by a sprint by the scoring or the assisting player [4]. As you can see sprinting is important to team sports and most other strength power sports. With that being said, it is important that one sprints in their regular training program/practice. During a sprint there is a great deal of hamstring activity as seen by EMG, some studies have reported peak activity during the terminal swing phase where as others have found peak hamstring activity in the stance phase (figure 3) [13]. Strength at length becomes important during these phases of running (terminal swing phase & stance phase) due to the lengthening seen during these phases, in some cases ~12% in some hamstring muscles [13]. The three biarticular hamstring muscles (ST, SM, BFlh) all have different responses to over ground sprinting. During the terminal swing phase the BFlh has the largest eccentric lengthening (~12% from baseline), SM produces the highest force, the ST displays the greatest eccentric lengthening velocity [13], with an understanding of the kinematics of sprinting and that sprinting alone can improve hamstring strength, sprinting is an effective tool in the injury protection of your athletes [5]. There is an alternating theory about whether there is an isometric and not an eccentric contraction in the terminal swing phase [17]. The question now becomes should we really be focusing all our time on the eccentric hamstring exercises? From a practical standpoint it does make sense there is an isometric phase during the terminal swing phase; you cannot switch from eccentric (terminal swing phase) to concentric (transition to initial contact) without having an isometric phase no matter how brief it may be (figure 3). However, with this information I am not completely sold on the idea that the hamstring operates solely in an isometric environment as we know from a great deal of evidence that the hamstring does lengthen during this terminal swing phase [5, 13, 16], but given the data and the speed at which research is being published I reserve the right to change my mind with more evidence. None the less, with this understanding it would be wise to include both eccentric and isometric hamstring exercises in athletes’ programs; with isometric exercises I will more likely than not use long muscle lengths as that has been shown to be better for the development of the hamstring muscle architecture and from a muscle specificity standpoint[6]. During the terminal swing phase the hamstring is exposed to extreme lengthening [6], integrated exercises expose hamstring muscles to long muscle lengths, examples will be discussed later. Moreover, this is why I am a firm believer that both sprinting and eccentric/isometric resistance training should be included in a resistance training program as both build a high level of resilience in an athlete. Sprinting works two folds: hamstring eccentric strength as well as running specificity as that is what they are doing in their sport. Having both sprinting and eccentric hamstring work in your program helps build the bridge to hamstring resiliency. Lastly, as stated before sprinting and eccentric hamstring training are only a piece of the puzzle albeit a significant piece [8].

Before I get into what a program can look like I wanted to discuss the use of what I call banded hamstring curls (figure 5). Banded hamstring curls are something that I first heard Louie Simmons of Westside Barbell discuss; I was truly fascinated with it as he discussed how it helped his lifters and the development of their ligaments and tendons. After trying it with myself and seeing benefits (more on this later) to it I started looking into the underlying physiology of it all (more on this later). There aren’t any studies that use bands in this manner, so it was a combination of piecing ideas together and looking at it from a pragmatic standpoint and ask myself whether or not I was seeing the benefits of its use in my programming. In the late swing phase when the thigh reaches its highest point and the knee starts to extend there is a great strain put on the hamstring tendons [17], during the Nordic hamstring exercise near the end range of motion there is also a great strain put on the tendons. Many athletes have complained of a sharp pain, discomfort, etc. when performing this exercise and this makes them reluctant to control the entire lowering portion of the movement, some athletes described to me saying, “it feels like it is going to rip”. To combat that “ripping” feeling I have implemented the banded hamstring curls. I had 12 of my rugby athletes and split them down the middle, one half performed banded hamstring curls and the other half did not. Nordic hamstring was tested before we started the intervention and 10 out of 12 athletes reported pain when trying them. After 4 weeks on the same program we moved to Nordic hamstring exercises and the banded group reported no pain (1 athlete in this group reported no pain at the onset of intervention) while 4/5 athletes in the no banded hamstring curl group still reported pain (1 athlete in this group reported no pain at the onset of intervention). This gave me all that I really needed to know, and I knew it was something that worked but could not fully understand why. Going back to the physiology of the exercise and piecing ideas together to come to a conclusion. Blood flow, oxygen demand, and collagen synthesis increase with mechanical loading [7], the banded hamstring curl is done with low resistance but high volume which leads to a high level of mechanical loading. The speed at which you are performing the exercise leads to a high level of eccentric force as the band shoots your leg forward the athlete must stop the reversal action of the band and pull it back to them, eccentrics are used with athletes dealing with tendinopathy issues [18]. Furthermore, when we look at the work of Keith Barr we understand that tendons can be trained via exercises that are short in duration (<10 mins) and limited range of motion [2]. When looking at the banded hamstring curl exercise it creates a high level of mechanical loading, a great deal of eccentric forces, and done in a limited range of motion. Although the evidence is not perfect, through deductive reasoning I can say the banded hamstring curls are a big reason the athletes don’t feel the sharp pain in the back of their knee, how much of a difference does it make? I am not sure, but it is qualitative and not quantitative evidence. All in all, I feel it is something that you should put in your program, sets and reps will be discussed in subsequent sections.

FIGURE 5.

I am going to outline a program that I used with my academy rugby athletes. I will display the sets and reps of the hamstring exercises only. At the time we started implementing these exercises athletes were already proficient in their resistance training technique and we could take out the idea of a learning effect as one of the reasons we saw improvements. I will also outline the days we sprinted, I will not go into detail around sprinting distances only acceleration or max velocity focus as I feel it’s important you marry the hamstring exercises with the sprints to limit any overuse injuries (figure 6). (Figure 7. is a video database of all exercises in figure 6.)

FIGURE 6.

FIGURE 7.

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