Evidence-Based Hamstring Strain Management

Hamstring strains are among the most common injuries that plague runners. Because of their popularity, researchers are constantly seeking the best way to treat these strains. Here’s a summary of recommendations to-date with regard to best evidence based management for hamstring strains from leading medical researchers issued in JOSPT (Journal of Orthopedic Sports Physical Therapy March 2022), plus my clinical pearls and recommendation based on my own patient experiences.

What a Hamstring Strain?

Hamstring muscle group consist of three muscles in the back of the thigh: biceps femoris, semimembranosus, and semitendinosus. The biceps femoris muscle is the most common muscle to be strained from overloading while the semimembranosus muscle is the most common hamstring muscle to be overstretched.

Biceps femoris is the most common hamstring muscle to strain. The mechanism of action is typically an over-loading (force) or over stretching (lengthening) of this muscle during the swing phase of running, right before the foot hits the ground. This is when there is maximal lengthening and eccentric load to this muscle. The other common mechanism of strain is overstretching the semitendinosus muscle. For example, this can occur while practicing yoga and standing with your foot planted, then bending over and taking the muscle pass its length under load.

Another way athletes strain their hamstring is when the hip is maximum flexed (thigh forward towards the chest, such as hurdlers or kicking a soccer ball) the knee is maximally extended (straight). If there is not adequate length of this muscle for this physical movement, this can lead to a micro-tearing over time with distance runners. When participating in activities of a high load and impact, or where more force production is required, you can have a full rupture or tear of this muscle, called macro-tearing.

What are the grades of hamstring strains?

Hamstring Strains for runners are typically graded in three stages, grade 1-3. Grade one is the most common, encompassing mild tearing and overloading. There typically won’t be any bruising and it will resolve usually in a 2-3 weeks with the right management. A grade one strain will have local pain, tightness, possible cramping in the back of the thigh, and slight pain with muscle stretching or contraction. Stiffness may subside immediately after activity, but will return following activity. There tends to be minimal loss of range of motion, usually less than 15°.

Grade two describes a moderate strain, where the muscle stays intact but the pain will cover a larger area than in a grade one strain. There is greater pain of muscle while stretching, stiffness, weakness, possible bruising, limited ability to walk typically for 24 to 48 hours after injury, and the range of motion deficits is about 16 to 25°.

A grade three strain is a severe strain, with a complete tear of the muscle. There will be swelling and bleeding, and it can be extremely difficult to walk typically and there significant restriction to range of motion, typically by 26 and 35°. A grade three strain usually requires imaging and a referral to get an MRI in order to get the exact location and severity of a tear, which is necessary to help determine prognosis and proper management.

Do I need an X-ray for a hamstring strain?

Imaging is not typically needed for hamstrings that are grade one or grade 2 because they don’t really change the clinical treatment outcome course for these injuries. And evidence supports that MRI does not actually improve the prediction of return to sport be on the clinical examination.

Runners with Hamstring strains should meet with a doctor to understand the severity of the strain and begin steps to recover.

The risk of reoccurring Hamstring strains

Hamstring strains can cause loss from time competition and running generally for 3 to 28 days, depending on the severity of the injury. Unfortunately, re-injury rates are very high – those who have had a previous hamstring injury are 3.6 times more likely to have a reoccurring hamstring strain in the future. In fact the biggest risk factor for a hamstring strain is having had a previous hamstring injury. Often times this might be attributed to an inadequate rehabilitation from the initial hamstring injury, and also premature return to running and exercise. Those that return to running less than eight weeks after after a hamstring injury have a higher rate of re-injury.

Risk factors for Hamstring injuries

Previous hamstring injury and age are the biggest risk factors for hamstring injury that are non-modifiable (meaning they cannot be changed). Those who over 23 years old are at a greater risk for injury than those under 23 years old. Height and weight (body max index) are not a risk factor for hamstring injuries.

Modifiable risk factors are those that can be altered, such as muscle characteristics and muscle performance. This can include hamstring strength and length. Hamstring flexibility is not a risk factor for injury and there’s weak evidence to support hamstring weakness as a risk factor for injury. However, there is evidence to show that altered trunk and gluteus maximus activity and abnormal motor control are risk factors for hamstring injury.

What this might look like is your pelvis tipping too far forward when you run. Imagine your pelvis is a soup bowl and you’re spilling that soup bowl forward towards your toes, which puts excessive strain on the back of the pelvis where the hamstrings attach to the sit bones. When you lengthen that leg in front of you, that puts even more stretching tension on the hamstrings and the sit bone where the hamstring muscles attach, increasing the risk for a strain.

How to heal from a Hamstring strain

The healing phase for hamstring injuries for runner s includes three phases: inflammation, proliferation and remodeling. The inflammation phase usually last 3 to 5 days, which is the majority of the healing. It is important not to overload or stretch the muscle at this time. Doing the proliferation phase it’s going take several weeks, usually up to 21 days. This is where your symptoms are getting better but there’s a lot of repair going on to the collagen in the vascularization of the tissues. You will experience a lot of stiffening and swelling in the muscle during this time. The collagen remodeling phase is the longest phase, and can last even up to 2 years depending on the severity of the strain.

In all, runners with hamstring strains make take a few weeks to up to two years to recover.

How to reduce risk of re-injury

As mentioned earlier, there’s a higher risk for re-injury when you return to running within eight weeks. However, there’s a lower risk of a hamstring strains of injury with individuals who perform agility exercises and core stabilization (7.7%) exercises after injury compared to those that only do stretching and strengthening alone (70%). The average to return to play is 23 to 48 days with re-injury rates at 9.1% to 63.3%. Grade one injuries have an average return to play time of 25 days. Grade 2 injuries have an average return to time play of 30 days, and grade three strains have an average return to play time of 75 days with rehabilitation.

Exercises for treatment

Eccentric strengthening and loading training of the hamstrings is specifically important for remodeling these muscles and tendons. Those programs that do not include eccentric training have a significant risk factor for re-injury and delayed return to play. It’s also important to not return to play before you’re ready, as it significantly increases the re-injury rate.

The number one evidence-based exercise for hamstring strengthening is the Nordic hamstring curl. Start in a kneeling position where your feet are stabilized and you’re holding a neutral pelvis position using body weight to start. Knees are bent 90° and you lean forward, trying to lower your body towards the ground and working the hamstring muscles, which gets gets maximally centric load. This is a very challenging exercise and should only be initiated during the appropriate time of rehab depending on the grade of the strain and each individual athletes specific needs.

The nordic hamstring curl is an excellent hamstring strain prevention exercise for runners and should be performed twice a week while week to three times a week in the off-season of training. Recommendations for dosing the Nordic hamstring curl can vary anywhere from two to three repetitions once a week up to three sets of 10 repetitions a few times a week. This should be a gradual progression because it is quite a bit of load on the hamstrings, so make sure that you get evaluated first to know proper dosing for your body.

Other high-quality exercises to improve hamstring eccentric and strengthen loading include the double leg dead lift and a high hip straight knee hamstring bridge (on your back and your feet are elevated on a box something little bit higher), hip extension on a Glute hamstring raise machine, and single leg dead lifts.

Other exercises to help decrease the hamstring strain risk for runners would be core stabilization and hip strengthening exercises, such as planking and bridging. Pilates reformer work can be extremely effective at eccentric loading of the hamstrings and working on core stabilization and lumbopelvic control in different variations that help to safely and progressively load the hamstring both in length and strength needed for running.

Progression of recovery from Hamstring injury

There needs to be normal, pain-free walking before you start any kind of jogging or running. After that criteria‘s passed, you can start some very slow speed jogging without pain. If you can do pain-free isometric contraction against a submaximal force, about 50 to 70% of your max resistance of the knee bent position, you can pass phase 1 of rehab. In phase 2, you need to have have full strength of the hamstrings without pain during a prone knee flexion test, in the knees bent position, and during normal muscle length. You should also have pain-free forward and backwards jogging with moderate intensity. The phase 3 return to running decision criteria is more individual-specific, depending on what kind of running the athlete is getting back to.

The course of progression will include plyometric training and agility training, plus running-specific drills such as A and B skips, lunge jumps, strides, bounding, and lateral lunge jumps.

In summary, Hamstring strains can be extremely frustrating for runners. It’s important to be proactive and a little more conservative because the re-injury rate is so high. The biggest mistake you can do is return to running or exercising too quickly, especially under that eight-week range. Aging runners need to ensure they are working on improving the muscle properties, including eccentric loading, strengthening, and improving hamstring length.

Getting a functional movement screen performed twice a year , just like like a dental cleaning twice, is a great way to reduce risk for injury and identify movement and musculoskeletal impairments that might put a runner and risk for injury. As the saying goes, an ounce of prevention is a pound of cure! Contact us to learn more about hamstring strain treatment for runners.