A pulled hamstring muscle, also commonly called a muscle strain, is an injury to one or more of the three muscles (biceps femoris, semimembranosus, and semitendinosus) at the back of the thigh. It often occurs when sprinting or kicking but runners, joggers, and sprinters can also experience this painful condition when a rapid contraction or a violent stretch of the hamstring muscle group occurs.
Hamstring injuries are also commonly seen in recreational sports – most commonly water-skiing. Despite the mechanism, all-cause varying degrees of tearing within the muscle fibers resulting in pain and reduced function.
Hamstring strains are a heavily researched topic, meaning we’re provided with numerous high-quality systematic reviews to examine what might predispose someone to a hamstring injury.
Flexibility and muscle length
Hamstring flexibility, although usually thought to predispose someone to a hamstring strain by the general public, has not been shown to have a significant association with the rate of injury in four different studies included in the systematic reviews.
One particular paper in 2020 which looked at risk factors for hamstring strains reports, “flexibility, mobility, and range of motion provided limited value as stand-alone risk factors”. Resultantly, where reducing hamstring strain injury risk is your goal, time spent foam rolling, stretching, using massage guns and other similar interventions targeting your hamstring muscles should likely be spent elsewhere.
A 2020 systematic review which looked at risk factors for hamstring strains found that reduced hamstring strength qualities, including both endurance (seen on single leg hamstring bridge and eccentric leg curl (Nordic curls))- and strength on a variety of testing was associated with an increased risk of hamstring strain injury.
They also found that baseline strength deficits were associated with a greater risk of hamstring injury in a number of studies, meaning that the weaker your hamstrings were upon being tested, the higher the likelihood of experiencing a hamstring strain.
We know a hamstring strain is essentially more force being applied to the hamstrings than it is able to handle, so it makes sense that the stronger they are, the less likely they are to be injured.
Training load and running exposure
Training load refers to the workload of the person or athlete. The higher the training load, the more force placed through muscle groups including the hamstring, and potentially the higher the muscle overload and risk of injury.
Training load is REALLY important, particularly in the area of injury prevention and avoiding hamstring strains. This is demonstrated in a number of studies. One, in particular, showed that increases in high-speed running exposure were associated with a greater risk of index hamstring strain injury, particularly where athletes had sharp spikes in their running exposure or intensity (within the previous 7-14 days).
This finding was mirrored in a study in 2010 that looked at factors that increased hamstring injury risk found positions in sporting populations that have larger running demands also posed an increased risk of hamstring strain injury. This is likely due to the fact that these athletes possess hamstring muscle groups with high levels of fatigue.
Whilst we know exposing our muscles to training allows for positive changes (improvements in strength and conditioning), we need to find the balance between seeking these positive adaptations whilst staying within limits that are protective against hamstring strain injury and also allow for adequate recovery time.
If we can systematically, gradually, and progressively plan out the training load of individuals, so as not to expose them to too much force in too short a timeframe, we can go a long way to reduce the risk of a hamstring strain.
Numerous studies referenced in a 2013 systematic review that looked at risk factors for hamstring injury in sport have found that athletes who are older are often at greater risk of a future injury. The conundrum with age is that ‘old’ is difficult to define, but there seems to be a link to an increased risk of hamstring strain injury in athletes as young as 24 years of age.
History of previous injury
A history of a previous hamstring strain, either in runners or other sportspeople, was one of the most commonly reported significant risk factors for recurrence. The studies included in the systematic review, found “ athletes with a history of hamstring strain were between 2 to 6 times more likely to suffer subsequent strains”. Additionally “most recurrences happened soon after return to sport” (generally within the first 8 weeks) however, the risk remained significant over time. AFL footballers in particular remained a huge 3 times more likely to suffer a recurrence even a year from the initial injury.
Non-hamstring-related injuries of the lower limb were also associated with an increased risk of a hamstring strain. For example, athletes with a previous calf injury were 50% more likely to suffer a hamstring strain, and those with groin-related pain were also at greater risk. The theory behind this finding is that if there’s a weakness in the chain, the muscle groups either closer to the trunk or further away will need to absorb more force and thus become more susceptible to injury.
Interestingly, there’s also a link between athletes who’ve suffered a previous ACL injury, with a huge 70% increase in the risk of a hamstring strain. The underlying mechanisms responsible for the increased risk following ACL injury are unclear, but reduced proprioception, strength deficits, and altered gait could contribute whilst ongoing deficits due to the graft used may also be a factor according to a 2019 study on eccentric knee flexor weakness in football players.
The most common symptom reported with a hamstring strain is a sudden moment of onset, whereby you ‘feel’ something has happened in the injured leg. This can be associated with mild to severe pain in the back of the thigh. Occasionally, people may report a ‘popping’ or ‘tearing’ feeling at the time of onset. Thereafter, depending on the severity and grading of the strain, there may be swelling and bruising that shows, sometimes taking even a few days to present.
Unless there is severe swelling and bleeding, there shouldn’t be any reported numbness, tingling, or weakness closer to the foot (if this is the case, you may need to seek medical help to ensure you aren’t suffering from compartment syndrome or from sciatica).
You may experience pain on stretching activities, such as trying to put your shoes on or pick something up from the floor, or pain and weakness in activities that require bending your foot up behind you.
Rehabilitation and Injury Prevention
Rehabilitation is particularly important following a hamstring strain, especially for the athletic population involved in running and explosive activities. An injured hamstring is essentially a weaker hamstring, meaning it has a reduced ability to withstand high forces, such as those seen in sporting endeavors and running.
This underpins the key principle of rehabilitation – we need to ‘raise the ceiling’ of the capacity in the hamstrings to prevent overload and subsequent injury. This is often started early (from about 2-3 days post-injury) and into bearable pain levels to ensure recovery time is facilitated in the best time frame possible.
Injury prevention of hamstring strains serves to address the modifiable risk factors addressed above. In terms of strength, there are two important studies that have examined how we can look to prevent hamstring strain injury through exercise.
A 2019 study that looked at the effect of the nordic hamstring exercise on hamstring injury prevention demonstrated a targeted eccentric strengthening program can reduce hamstring strains by 50% in athletes who perform regular and repeated bouts of high speed running.
Similarly, a 2011 study that looked at the preventive effect of eccentric training on acute hamstring injuries found that in soccer players who also completed an eccentric hamstring strength protocol reduced the rate of hamstring strains by over 60%. Also, the protocol reduced recurrences by 85% when compared to athletes who did their ‘usual’ training.
When looking at training load, ensuring adequate recovery through good training planning, sleep, and nutrition, whilst minimising the effect of fatigue by listening to your body and using other measures that assess perceived fatigue are high-value methods for preventing hamstring injuries. When implementing new methods of training or quicker, hillier, or increased volume of work, look to do this in a gradual fashion allowing the body to adjust and adapt.
Recommended treatments for hamstring injuries
A sports medicine and evidence-based treatment for muscle injuries can be summarised by the acronym ‘peace and love’.
Protection: Unload and restrict movements that increase pain for the first 1-3 days after injury
Elevate: Elevate the injured limb higher than the heart as often as possible over the first 1-3 days.
Avoid anti-inflammatories: These may negatively affect long-term tissue healing. Proper healing and tissue regeneration is supported by the inflammatory process.
Compression: Applying a compressive bandage or taping can be useful in limiting tissue swelling and bleeding
Education: It’s important to receive the right information on the benefits of an active approach to healing. Passive treatments (eg. ultrasound machines, massage guns, etc.) have insignificant effects on pain and function compared with an active approach.
Loading: Exercising the injured area with load should resume as soon as symptoms allow. Optimal loading can be performed into pain as long as it doesn’t exacerbate symptoms afterward, serves to promote healing, scar tissue formation, and builds tissue tolerance to reduce the likelihood of further injury in the future.
Optimism: stay realistic, but be sure to remain optimistic to improve your chances of optimal recovery. Pessimistic expectations negatively influence outcomes and prognosis following injury.
Vascularisation: injury management should include some cardiovascular exercise. Pain-free cardiovascular activity is a motivation booster and it increases blood flow to the injured structures to improve function and reduce the need for pain medication.
Exercise: Evidence supports the use of exercise therapy in the treatment of soft tissue injuries. As noted above, regaining strength is a key component in ensuring you don’t reinjure your hamstring and can return to your chosen activities and perform at the level you’d like.
By and large, the prognosis of a hamstring strain is positive. Obviously, it depends on the particular characteristics of the individual, including age, ethnicity, previous history of strains or injuries amongst other things.
Importantly, it also depends on the level of physical activity you plan on returning to. If you don’t play sport or exercise at any intense level, and only need to be ‘fit for life’ and general activities of daily living, your prognosis might be better than someone who’s older and is trying to return to a sport involving sprinting and explosive movements.
Ultimately, if you’re doing everything within your power to positively affect the modifiable risk factors, including a tailored and progressive exercise program from a knowledgeable physiotherapist, you can rest easy knowing that you’ve done everything in your control.
Below is a guide to return to full training times depending on the severity of the strain as per a study which looked at hamstring injury outcomes:
Exercises for hamstring strain rehabilitation
The hamstrings are what’s called a two-joint muscle, which means that it acts over two joints, the hip, and the knee. This is why it is important hen rehabilitating hamstrings after an injury to perform exercises that target movements at both the hip and the knee.
Below are some examples of exercises (from easiest to hardest) that may be used in a typical hamstring strain rehabilitation program.
The last exercise in the video, Nordics, are vital from an injury prevention perspective post-rehabilitation of a hamstring injury. By incorporating Nordics into your training regime, it can reduce the chances of sustaining a hamstring injury by a whopping 50%!
Below is a Nordics program that slowly builds up in volume.
Frequently Asked Questions
How can I sleep with a pulled hamstring?
Taking pain relief, such as panadol or Voltaren, can be helpful in the early stages of a pulled hamstring to help you sleep.
How can I avoid hamstring injuries?
Avoid sharp spikes in your training load and engage in regular strength training (2-3x per week) for your hamstrings.
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