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Hamstring muscle strains that keep coming back

Here’s how the story often goes…

You spent time, weeks perhaps, being ‘good’ and resting your hamstring muscle strain, while you went stir crazy, jealously watching your friends continue playing sport and running races. Your hamstring finally felt better, so you euphorically went back to sport / running, and a short time later... it went again! Infuriating!! Now what!? Aaaaaargh!

In this blog, Steph Davies from Sports Physio Hwb and aims to explain what puts you more at risk of hamstring muscle injury and what you can do about it.

A bit about hamstrings

Hamstring muscle injuries are extremely common, especially in sports involving running. A hamstring ‘strain’, ‘tear’ or ‘sprain’ all really mean the same thing, and the severity of muscle injury is now graded 0-4 (previously 1-3) depending on how much of the muscle has been injured. The higher the grade, the longer it will take to recover.

It’s always helpful to start with some basic anatomy. The hamstrings are a big muscle group made up of the biceps femoris, semimembranosus and semitendinosus. They all start at the sit bone (ischial tuberosity) at the bottom of the pelvis, and come down the back of the thigh and attach just below the knee. The biceps femoris attaches below the outside of the knee, and the semimembranosus and semitendinosus below the inside. One of the interesting things about hamstrings is that they cross both the hip joint and the knee joint, so they can extend the hip (take the leg backwards) AND flex (bend) the knee.

When we run, one of the main jobs of the hamstrings during the swing phase of gait, i.e. when the foot is off the ground, is to lengthen under control (eccentrically) against the powerful quadriceps muscles at the front of the thigh.

There is one point, when at maximum stride length when sprinting, that the hamstrings are not only working hard eccentrically but also on a stretch – this is one of the most common times for the muscle to get injured.

So, now you have some background knowledge on how the hamstrings function, how does that apply to what you need to do about it?

Let’s start with some of the “modifiable risk factors” for hamstring strains, or in other words, stuff you can do something about to decrease the risk of it getting injured again.

1. Strength

We talked already about how the hamstring works eccentrically against quadriceps when running.

If there is a deficit in the endurance OR the eccentric strength in the hamstrings, particularly in comparison to the quadriceps (known as the hamstrings : quads ratio), then there is an increased risk of hamstring muscle injury as it is easily overloaded.

2. Power

How far can you hop on one leg? Is it the same on both sides? A recent research review showed that returning to running/sport before recovery of full power can also increase your risk of hamstring muscle injury.

3. Core muscle control

Research has also shown that poor trunk muscle stabilisation and control while running can increase the risk of hamstring muscle injury. It’s therefore important to address not just the hamstring itself, but any underlying biomechanical factors around the pelvis or spine that might need strengthening or improving.

4. High speed running exposure / training error

It makes sense that if there is an increased mechanical risk in hamstring injury with sprinting, then the risk overall is increased with a higher exposure to sprinting too.

There is also evidence that sudden increases in sprinting exposure in the past 7 to 14 days from what you are used to doing before, also increases the risk of injury. However, a gradual increase or build up can be beneficial in conditioning the muscle to that load. Gradual conditioning may in fact contribute to a decreased risk of recurrence.

There is conflicting evidence to suggest that decreased recovery between matches or races will increase the risk of hamstring injury – some studies say it does and others say it doesn’t – it probably depends on what your body is used to.

5. Flexibility

There is conflicting evidence for whether or not tight hamstrings increases your risk of an initial hamstring injury. However, poor flexibility in the hamstrings may increase the risk of recurrent strains.

That sounds simple enough. Or is it?

Unfortunately, there are also a few “non-modifiable” risk factors associated with hamstring muscle injury i.e. things that increase the risk of injury that, well, you can’t really do anything about.

1. Previous hamstring injury

When you’ve injured it once, your risk of it happening again is 2.7 x higher than had you never injured it before. This could be because of structural weakness and scar tissue being more vulnerable. That risk rises to 5 x higher if the hamstring was injured in the same competitive season – probably accounting for people who try to return to sport too soon.

2. Age

It’s a sad fact of life that injury risk increases with chronological age. This could be due to decrease tissue quality, or perhaps an increase in overall exposure to load.

Either way, age is not something any of us can do much about! So, it’s probably best just to be grateful to have made it to whatever age you are in this increasingly mad world and move on from this point!

3. History of Anterior Cruciate Ligament (ACL) injury

A new finding is that hamstring muscle injury risk is increased if there has been a previous ACL injury.

This may be due to hamstring deficit from the donor site for ACL reconstruction grafts, or perhaps ongoing knee instability requiring an increased load on the hamstrings.


Well done if you’ve made it reading this far!

Hopefully this gives you a guide and all the things that need addressing to do what you can do to decrease the risk of it happening again.

The best place to start would be a full physio assessment so we can identify your individual modifiable risk factors and put together a plan to address them, along with a graded strengthening and running conditioning build up.

Please get in touch if you would like some guidance with this – otherwise good luck, go and get this sorted and get back out there!


Green B, Bourne MN, van Dyk N, et al

Recalibrating the risk of hamstring strain injury (HSI): A 2020 systematic review and meta-analysis of risk factors for index and recurrent hamstring strain injury in sport

British Journal of Sports Medicine 2020; 54:1081-1088

Erickson LN, Sherry MA. Rehabilitation and return to sport after hamstring strain injury. J Sport Health Sci. 2017 Sep; 6(3):262-270

Brukner P, Nealon A, Morgan C, et al

Recurrent hamstring muscle injury: applying the limited evidence in the professional football setting with a seven-point programme

British Journal of Sports Medicine 2014; 48: 929-938

Pollock N, James SLJ, Lee JC, et al

British athletics muscle injury classification: a new grading system

British Journal of Sports Medicine 2014; 48: 1347-1351

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