The hamstring muscles, also called the hamstrings, are composed of three muscles on the posterior part of the thigh: the semitendinosus, semimembranosus, and biceps femoris. Their function includes facilitating hip extension and knee flexion.
Sports activities can lead to injuries in these muscles, which are robust and diligent. Nonetheless, there are measures one can adopt to enhance their strength and flexibility, thus ensuring injury prevention.
WHAT ARE THE DIFFERENT TYPES OF HAMSTRING INJURIES?
If you have experienced a torn or pulled hamstring, you are aware of the painful nature of this injury and its long recovery period. Normally, a hamstring tear or pull happens during either sprinting (such as in track and field or team sports) or stretching exercises (such as kicking movements).
There are three categories in which hamstring injuries can be classified, known as grades.
- Grade 1 (mild) hamstring injuries involve overstretching of the hamstrings with no tearing of muscle fibers. You might not be aware of the injury until after the activity is over. It may cause pain and tightness later, but typically no significant loss of muscle flexibility or strength.
- Grade 2 (moderate) hamstring injuries cause partial tearing of one of the hamstring muscles. Pain is typically felt immediately, and there can be a loss of muscle flexibility and strength.
- Grade 3 (severe) hamstring injuries involve the complete tearing of the muscle. The pain is sudden, sharp, and severe. Using the leg at all causes pain, and surgery may be required to repair the damage.
It is crucial to follow the guidance of a doctor or athletic trainer when dealing with pulled or torn hamstring symptoms in order to prevent aggravating the injury.
HAMSTRING ANATOMY
There are four muscles in the hamstring group, which include the Semimembranous, Semitendinous, as well as the long and short head of the Biceps Femoris.
Both the semitendinous and semimembranous muscles have their origins on the medial side of the ischial tuberosity, and they attach to the medial tibia and popliteal fascia at their distal ends.
The biceps femoris consists of two heads, each with distinct attachments and fiber directions. The long head begins near the outer part of the ischial tuberosity and sacrotuberous ligament, while the short head begins at the linea aspera and supracondylar ridge of the femur. These two muscles merge together lower down and connect to the fibula’s styloid process and the lateral tibial condyle, continuing directly into the lateral collateral ligament.
HAMSTRING FUNCTION
Building a focused rehabilitation or prevention plan requires a comprehensive understanding of the different functions of the hamstrings during the gait cycle.
Although many textbooks state that the hamstrings are mainly responsible for concentric knee flexion, this description does not accurately represent their role in locomotion. In reality, during the swing phase of walking, knee flexion is primarily a passive movement caused by intersegmental dynamics and the contraction of the gastrocnemius.
The hamstrings provide eccentric stabilization for the knee and sacroiliac joint, while also assisting in hip extension concentrically.
The main role of the semimembranous and semitendinous muscles is to act as eccentric stabilizers of the knee at the beginning of the stance phase, working together with the popliteus and ACL to restrict anterior tibial movement. Furthermore, they provide support to the glutes, acting as a synergist in hip extension.
The bicep femoris plays a crucial role in slowing down knee extension in the swing phase of walking. Furthermore, due to its connection to the ischial tuberosity, this muscle also contributes to the isometric stabilization of the sacroiliac joint upon foot contact.
MECHANICS OF A HAMSTRING STRAIN
The bicep femoris is the hamstring muscle that is injured most frequently, making up 53% of all hamstring injuries. When sprinting, the typical hamstring strain is usually a bicep femoris strain, while overstretching injuries commonly happen in the semimembranous and semitendinous muscles.
Through my experience, I have consistently observed that there are typically a few underlying variables that serve as the primary cause of any sudden non-contact injury. Here, I will outline the three principal factors that frequently contribute to hamstring strains.
1). PELVIC POSITIONING
I often discover that the main cause of these injuries is pelvic malpositioning, particularly an anterior pelvic tilt. Numerous studies have identified anterior pelvic tilt as a risk factor that can be altered in relation to biceps femoris strains. Let’s pause for a moment to contemplate how anterior pelvic tilt affects the hip and core muscles.
Maintaining a neutral pelvis, the hamstrings, along with the diaphragm, obliques, and glutes, play a crucial role in postural control of the innominate in the saggital plane. The coordination of these muscles allows for effective pelvic stabilization.
When there is an anterior pelvic tilt, the ischial tuberosity rotates upwards, leading to alterations in the length-tension relationships of the muscles surrounding the pelvis. As a result, the obliques, glutes, and diaphragm become inhibited, which puts extra demand on the hamstring muscles to keep the pelvis in the correct position. Individuals with anterior tilt often experience a feeling of “tight hamstrings,” but in actuality, their hamstrings are “locked long,” as they are overstretched and inhibited.
2). INHIBITION OF PRIMARY HIP EXTENSORS
When the gluteus maximus is weak and inhibited, it can lead to changes in muscle recruitment patterns, causing the hamstrings to take over as the main muscle for hip extension. This dominance of the hamstrings over the glutes significantly increases the strain on the hamstrings during contraction, making them highly prone to overuse injuries.
3). POOR ECCENTRIC HAMSTRING STRENGTH
A lot of training programs tend to prioritize the training of the hamstrings’ concentric contraction, but they often overlook the importance of developing eccentric strength. While concentric strength is essential for generating force, it is crucial to focus on eccentric strength for absorbing force. The majority of soft tissue injuries without contact occur due to tendon failure during the eccentric phase of contraction. When sprinting, the hamstrings experience significant demands in eccentric action to stabilize the knee and pelvis. If the hamstrings are not adequately prepared to handle high levels of eccentric stress, the risk of suffering a hamstring strain is greatly increased.
As a consequence of the mentioned dysfunctions, the hamstrings will face higher demands, ultimately resulting in overuse injury or tendon rupture. The conflicting requirements for eccentric and concentric actions often lead to excessive strain on the tendon when the heel strikes the ground during the gait phase.
The hamstring group experiences the highest activity just before and after heel strike during sprinting. The bicep femoris experiences its greatest amount of stress in its lengthening phase during the last 20% of the swinging phase, which helps slow down the extension of the knee. After this, the hamstrings need to go from lengthening to a short period of staying the same length at heel strike before they can start contracting to assist the gluteus muscles in extending the hip. This crucial shift from the end of swinging to the beginning of the stance phase is where a lot of hamstring strains are likely to happen.
WHAT CAN YOU DO TO PREVENT A HAMSTRING INJURY?
To avoid the agony of hamstring injuries and the long duration of recovery, it is advisable to prioritize prevention. Various exercises can enhance the hamstrings’ strength and flexibility. The choice of exercises should be based on factors such as the nature of your activities and the level of strain your hamstrings endure during those activities.
Some exercises that help strengthen the hamstring muscles include:
- Lying leg curls. Lie face down on a leg curl machine with the back of your ankles underneath the pad and your hips resting on the support. Bend your knees rapidly to bring your heels up, then slowly lower to the starting position. Repeat as appropriate for your fitness level and goals.
- Hamstring slides. Lie on the floor on your back with your legs bent at 90 degrees. Your heels should be under your knees and on workout sliders. Or you can wear socks and do the exercise on a hard floor surface at home. Raise your hips and move your heels away from your body until your legs are nearly straight. Pull your heels back to the starting position and repeat.
- Single-leg stability ball curl. Lie on your back with both feet on a stability ball. Raise your hips and bend one knee to pull that foot off the ball. Bend the other leg to pull the ball toward your body. Reverse the movements and repeat.
Some examples of stretches that target the hamstrings are:
- Hurdler stretch. Sit on the floor with your legs straight in front of you. Bring the sole of one foot in to rest against the side of your thigh. Lean forward slowly to give your hamstrings a good stretch, then return your torso to the upright position. Stretch each leg multiple times as needed.
- Hip flex. Stand in front of a chair. Put the heel of one foot onto the chair with your leg straight and your foot at a 90-degree angle to your leg. Slowly lean forward, attempting to touch your fingertips to your toes. Hold the stretch briefly, then return to the starting position. Stretch each leg multiple times as needed.
- Standing hamstring stretch. Stand and cross your right foot in front of the left so that both feet are flat on the floor with their outside edges touching. Keeping your knees straight, bend at the waist, moving your head toward your right knee. Hold this position for up to 30 seconds, then return to the starting position. Stretch each leg multiple times as needed.
HAMSTRING INJURY PREVENTION IS WORTH THE EFFORT
Investing time and effort in improving the strength and flexibility of your hamstrings is necessary, but the benefits are worthwhile as they lower the chances of experiencing a pulled or torn hamstring. Alongside the provided hamstring exercises and stretches, additional ones suggested by medical professionals, physical therapists, or athletic trainers can effectively safeguard you and ensure continued enjoyment of your favorite sports and activities.
