Updated: Feb 15
Understanding the three phases of how a strained or torn hamstring heals will help you to know what to do – and what not to do – during each phase to speed up your recovery.
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Hamstring Healing Phase 1: Clot forms and cleaning starts
What happens when you strain your hamstring is that you tear some of the fibres in that muscle. This can range from a mild strain, where only a few fibres are torn, to a severe one involving a large portion of the whole muscle.
Think of the muscle as a building that’s been damaged in an earthquake. The debris has to be removed before we can start repairing the building. In the case of your hamstring, the damaged muscle fibres and cells have to be taken away so that new ones can replace them.
Two things happen to your muscle during this phase, which lasts for about the first three to five days: A blood clot forms and inflammation sets in.
The blood clot, which is like an internal scab, is the ‘scaffolding’ to which the new cells that replace the damaged ones will attach themselves to. The job of the inflammatory cells is to absorb the damaged cells – clearing away the debris.
This is why it is not a good idea to take anti-inflammatories in the first three to five days after a hamstring injury. Inflammation is a really important part of the healing process. Research has found that if you heavily suppress the inflammatory phase with anti-inflammatories during that first period, you can actually slow down your healing process.
If your injury is really painful, ask your doctor if it’s OK to take something like paracetamol instead.
On that note, some people wonder about the use of ice during this phase, because ice also decreases inflammation. However, the effect of ice lasts only for a very short time, whereas anti-inflammatories are in your blood for six to eight hours per dose. So, as long as you use it correctly, ice is less likely to negatively impact your healing.
You should avoid stretching or any rigorous movements during this time, as this will damage the new ‘scaffolding’ and therefore also slow down the process of adding new cells. You may also further damage other muscle fibres because the whole muscle is a bit weaker.
Phase 2: New cells form
After about three to five days, depending on the severity of the injury, your hamstring healing process enters the regeneration phase. Your body starts forming new cells and these cells attach to that scaffolding – the blood clot. This goes on for about three weeks and overlaps with the next phase, which is the remodelling phase.
These new cells are not strong yet, and they are not oriented in the correct way. Healthy muscle cells and fibres are aligned in the direction of the force that they need to exert, all parallel to each other. The new muscle cells are more like a plate of cooked spaghetti – all jumbled up, which is typical of scar tissue.
Phase 3: New cells grow stronger and get organised
To get this scar tissue / new cells to line up correctly and get stronger, you need to ‘remodel’ it and signal to your body what you want it to do by means of tensing the scar tissue. You do this through following a progressive strength training programme.
Such a programme has to start with low load exercises that are appropriate for the current strength of your injured muscle. However, as your hamstring injury heals, the exercises should increase in intensity and complexity until your muscle is as strong as before you injured it. It can take anything from a few weeks to several months, depending on how bad your injury was and the type and intensity of activity that you would like to be able to do.
How does exercise remodel tissue?
Every time you do an exercise that's a tiny bit harder than what your new muscle cells and fibres are used to, but not too hard, the body goes ‘Oh, you actually want them to be stronger!’ In response, it rebuilds the muscle fibres fatter and stronger, and they can cope better with what is expected of them. It also senses in what direction these muscle fibres have to work and aligns them accordingly.
As soon as you're used to a certain level of rehab, you should increase the intensity of the rehab a tiny bit more, until you've reached your full strength.
Just resting an injury doesn't work. It may make the pain go away, but you're very likely to reinjure it if you go back to sport without doing rehab first. Just like you can't build strong muscles by just lying on the couch, you need exercise to strengthen those new cells slowly and progressively during the regeneration and the remodelling phases.
How we can help
Need more help with your injury? You’re welcome to consult one of the team at SIP online via video call for an assessment of your injury and a tailored treatment plan.
We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine. But at Sports Injury Physio we don't just value qualifications; all of us also have a wealth of experience working with athletes across a broad variety of sports, ranging from recreationally active people to professional athletes. You can meet the team here.
Hickey, J. T., et al. (2017). "Criteria for progressing rehabilitation and determining return-to-play clearance following hamstring strain injury: a systematic review." Sports medicine 47(7): 1375-1387.