Hamstring strains occur due to sudden or forceful movements that lead to excessive tension on the hamstring muscle group, leading to significant mechanical strain. Consequently, there can be differences in the extent of damage within the fibres of the musculotendinous unit.
Strains to the hamstring muscle group are prevalent in sports that involve rapid movements such as sprinting and jumping, as well as in contact sports like Australian Rules football, American football, and soccer, where there is a regular occurrence of quick eccentric contractions. Among these sports, soccer has the highest frequency of hamstring injuries. Hamstring injuries may also happen during recreational activities like water skiing and bull riding, where the knee is forcefully extended, causing injury.
There are three muscles that make up the hamstrings.
- The biceps femoris
- The semitendinosus and
- The semimembranosus.
Epidemiology/Etiology
The cause of a hamstring muscle strain is often obscure. In the second half of the swing phase, the hamstrings are at their greatest length and at this moment, they generate maximum tension. In this phase, hamstrings contract eccentrically to decelerate flexion of the hip and extension of the lower leg. At this point, a peak is reached in the activity of the muscle spindles in the hamstrings. A strong contraction of the hamstring and relaxation of the quadriceps is needed. According to “Klafs and Arnheim”, a breakdown in the coordination between these opposite muscles can cause the hamstring to tear. The greatest musculo-tendon stretch is incurred by the biceps femoris, which may contribute to its tendency to be more often injured than the other 2 hamstring muscles (semimembranosus and semitendinosus) during high-speed running.
Predisposing Factors/Risk Factors
Several potential risk factors have been suggested that could be involved in causing hamstring injuries.
- Older age
- Previous hamstring injury
- Limited hamstring flexibility
- Increased fatigue
- Poor core stability
- Strength imbalance
- Ethnicity
- Previous calf injury
- Previous substantial knee injury
- Osteitis pubis
- Increased quadriceps flexibility was inversely associated with hamstring strain incidence in a group of amateur Australian Rules footballers
- Players presenting certain polymorphisms, IGF2 and CCL2 (specifically its allelic form GG), might be more vulnerable to severe injuries and should be involved in specific prevention programmes
- Tight hip flexors
- Previously associated lumbar spine abnormalities. Kicking and executing abdominal strengthening exercises with straight legs have been identified as possible contributory causes of lordosis. The anatomical reason seems to be that the iliopsoas muscle group is primarily involved in kicking and straight leg raising or straight leg sit-up exercises and contributes to strengthening this muscle’. Therefore, it is possible that certain athletic activities and training methods that exacerbate postural defects may also predispose the player to injury.
When running or kicking, the hamstring muscles will experience elongation as the hip flexes and the knee extends. This elongation could go beyond the muscle’s mechanical limits or cause microscopic muscle damage. Additionally, there is a risk of hamstring injuries due to the possibility of biceps femoris muscle contracting in an uncoordinated manner caused by the dual nerve supply.
A new discussion is underway regarding differences in muscle architecture within the hamstring group. The biceps femoris muscle has two distinct sections, the short head and the long head. The short head has longer fascicles, which means it can stretch more and has less risk of injury during eccentric contractions. Additionally, it has a smaller cross-sectional area compared to the long head. In contrast, the long head has shorter fascicles and is more prone to accumulating muscle damage due to repeated over lengthening.
An exaggerated tilt of the pelvis towards the front can cause the hamstring muscles to be stretched to longer lengths, which has been suggested in certain studies to raise the likelihood of experiencing strain injuries.
Hamstring strains are classified into three groups based on the level of pain, weakness, and range of motion limitation.
- Grade 1 (mild): just a few fibres of the muscle are damaged or have ruptured. This rarely influences the muscle’s power and endurance. Pain and sensitivity usually happen the day after the injury (depends from person to person). Normal patient complaints are stiffness on the posterior side of the leg. Patients can walk fine. There can be a small swelling, but the knee can still bend normally.
- Grade 2 (medium): approximately half of the fibres are torn. Symptoms are acute pain, swelling and a mild case of function loss. The walk of the patient will be influenced. Pain can be reproduced by applying precision on the hamstring muscle or bending the knee against resistance.
- Grade 3 (severe): ranging from more than half of the fibres ruptured to complete rupture of the muscle. Both the muscle belly and the tendon can suffer from this injury. It causes massive swelling and pain. The function of the hamstring muscle can’t be performed anymore and the muscle shows great weakness.
Hamstring Strain Symptoms
Listed below are some symptoms to help you identify if your pain is due to a hamstring tear. It’s essential to keep in mind that the severity and location of the tear can cause variations in the symptoms of a hamstring strain.
Included in the symptoms are:
- Pain
- Soreness
- Swelling
- Muscle spasms
- Stiffness, limited range of motion
- Bruising
- Weakness
- Discomfort during movements that involve the muscle
Potential causes of hamstring strains
Athletic or physical activity is usually associated with most cases of hamstring strains. It is highly likely that you can pinpoint the exact time and circumstances of your injury if you suffer from one. Here are some factors that may increase the likelihood of experiencing a hamstring strain:
- Poor flexibility in the hamstrings, glutes, or calves
- Sprinting without a proper warmup
- Sudden stops from sprints
- Overuse or fatigue – engaging in physical activity that the trainee did not properly build up to over time.
- Poor warm up routine before physical activity
- Muscle imbalances: The quadriceps and hamstrings are a force couple which means they work together to perform movements in the knee. As a result of, if one muscle group is weak the other will compensate. This may result in injury. It is also important to evaluate the posterior kinetic chain: glutes, hamstrings, lumbar spine muscles, and calves.
Who is most at risk for hamstring strains?
As previously stated, hamstring strains and tears are often linked to sports and physical exertion. Therefore, the following information should not be unexpected. However, there are specific sports where hamstring injuries occur more frequently.
- High school, collegiate, and professional athletes. There is an increased incidence rate with athletes that play football, soccer, and track & field.
- People that have had prior hamstring injuries.
Hamstring strain treatment options: What can you do?
RICE
The RICE protocol, comprised of rest, ice, compression, and elevation, is well-known to many. Along with following the standard RICE procedure, ensure that any activities that lead to heightened pain, discomfort, or swelling are avoided.
Medication
Over-the-counter anti-inflammatory medications such as Tylenol or Ibuprofen may prove helpful in the beginning. However, it’s important not to rely on these medications in the long-term.
Physical therapy
Receiving physical therapy for a hamstring strain entails a comprehensive treatment plan, encompassing modalities, therapeutic exercise, therapeutic activity, and manual therapy, specifically designed for you. The Physical Therapist outlines this plan during your initial evaluation on your first visit, tailored to your specific needs.
Ice, electrical stimulation, heat, and ultrasound are all different types of treatment options. Ice can be used to reduce swelling and discomfort in the initial stages of an injury. Electrical stimulation may offer pain relief. Later on in the healing process, it may be beneficial to use moist hot packs to increase blood flow, alleviate pain, reduce muscle spasms, and improve flexibility in soft tissue. Finally, ultrasound can be helpful in promoting circulation throughout any affected muscle fibers.
Rehabilitation consists of an indispensable part known as therapeutic exercise, which plays a crucial role in the healing process by boosting blood circulation in the injured area. Moreover, exercise fosters increased strength, joint stability, muscle elasticity, balance, proprioception, and endurance while it provides an added value of releasing endorphins that elevate mood and improves sleep that positively contributes to recovery.
The therapeutic intervention consists of functional tasks such as squatting, lifting, and bending to improve functional mobility. Additionally, dynamic activities will be introduced to the patient. The therapeutic activity will also include patient education to guarantee proper form, speed, muscle activation, posture, body mechanics, and lifting techniques while performing activities. This is important in avoiding reinjury.
The Physical Therapist or Physical Therapy Assistant uses manual therapy, which is a treatment that involves using the hands, to alleviate musculoskeletal pain. For a hamstring strain, the manual therapy is initially gentle to promote healing and decrease swelling. In the later phase, it may involve deep friction massage, stretching, and instrument-assisted techniques to remove any scar tissue.
Diagnostic Procedures
Allowing the patient to explain the nature of the injury usually suffices in identifying the majority of acute injuries. However, to confirm their assessment, some examination of the hamstrings is necessary.
In situations where the therapist’s uncertainty persists, requesting medical imaging can help rule out other potential causes.
- Radiographs: a good thing about radiographs is that with that kind of imaging, it’s possible to differentiate the etiology of the pain. It can differentiate in muscular disease (e.g muscle strain) or a disease of the bone (e.g. Stress fracture).
- Ultrasound (US): this kind of imaging is used a lot because it is a cheap method. It is also a good method because it has the ability to image muscles dynamically. A negative point about Ultrasound is that it needs a skilled and experienced clinician.
- Magnetic Resonance Imaging (MRI): MRI gives a detailed view of muscle injury. But sometimes it may not be clear according to the images. If that happens, the therapist must rely on the story that the patient told him (see characteristics/clinical presentation).
An MRI examination was performed with the aim of discriminating the two primary categories of muscle damage: injuries caused by direct trauma or injuries caused by indirect trauma.
- Within the group of injuries due to indirect trauma, the classification brings the concept of functional and structural lesions. Functional muscle injuries present alterations without macroscopic evidence of fiber tear. These lesions have multifactorial causes and are grouped into subgroups that reflect their clinical origin, such as overload or neuromuscular disorders. Structural muscle injuries are those whose MRI study presents macroscopic evidence of fibre tear, i.e., structural damage. They are usually located in the Musculotendinous junction, as these areas have biomechanical weak points.[18] Some studies screened patients after hamstring injuries and they concluded that, normalisation of this increased signal intensity in MRI seems not required for a successful return to play (RTP)
Hamstring Strain Exercises
The part of the article you have been anticipating is here. It has been observed in the field of physical therapy that individuals who commit to performing therapeutic exercises for hamstring strains on a consistent basis experience better results and a reduced risk of re-injury.
This is a brief workout regimen designed to be completed in under 20 minutes, which can aid in the recovery of your hamstring. The exercises detailed are intended for the initial stage of recuperation, during which early action is essential. After stabilizing your symptoms and feeling prepared to advance, there is a progression plan to adhere to.
Hamstring Stretch
This hamstring stretch offers a mild extension to the hamstrings and may have been featured in our previous posts. While there are multiple ways of stretching the hamstrings, this one is preferred for rehabilitation purposes. Lying on your back provides an unburdened stretch, unlike the seated hamstring stretch that might be overly intense in the initial stages. It’s your call to decide whether this one suits you.
To perform this, lie down on your back and bend the knee that is not affected to relieve pressure from your back. The affected leg must remain straight, and the strap should be hooked beneath the foot. Use your arms to maneuver the strap and lift your leg while maintaining a straight knee until you sense a stretch. Keep the stretch for 30 seconds, repeat three times.
It’s important to remember that stretching ought to be done without discomfort. If you feel pain, you may be overreaching into the stretch. Remember that rehabilitation takes time. It’s preferable to do what you’re capable of presently, knowing that you can improve gradually in the future.
Prone Hamstring Curls
This is a fantastic workout to softly engage the hamstrings. If you’re familiar with utilizing a hamstring curl device at the fitness center, you’ll see that this activity is quite comparable. However, the contrast here is that we’re not incorporating any additional outside weight or pressure.
To perform this exercise, lie on your stomach and place your feet at the edge of the bed for comfort. Slowly bend your knee to a 90-degree angle and then lower it back down to the bed in a controlled manner. Complete 3 sets of 15 to 30 repetitions, taking a 30 to 60 second break between each set.
Straight Leg Raises
Reintroducing some strength to the hip flexors and quadriceps can be achieved excellently with this exercise. Just as with the other exercises, we’ve opted for one that requires lying on the back without the use of external resistance. It’s important to keep in mind that this exercise is meant for the initial phase of healing following a hamstring injury, and that normal strengthening activities can be reintroduced at a later time.
To perform this exercise, lie on your back and ensure that the affected leg is straight. Then, bend the unaffected leg while elevating the affected leg until it is aligned with your other knee. It’s essential to conduct the movements at a regulated pace and keep the affected knee straight. Take breaks of 30 to 60 seconds between sets and aim to complete 15 to 30 repetitions in three sets.
