What is a Muscle Strain or Tear?

Have you ever wondered if that muscle pain you feel is a strain or actually a tear… is there a difference?

In this article we are going to clear up the confusion and talk about what actually happens when you have a muscular injury.

structure of a muscle

What Makes-Up A Muscle?

Before we dive into the types of tears, let’s talk about what makes up a muscle. In anatomy books, muscles look like a single structure with a name.

As athletes, you are already familiar with some of the names of these muscles (i.e., hamstring, quad, glutes, etc). These pictures are actually a little misleading. 

Our muscles are not individual structures. In the picture above, you can see that each muscle is made up of hundreds of individual muscle fibers. These fibers are then grouped together and wrapped in connective tissue (fascicles in the picture above).  All of these groups are then joined together and wrapped in more connective tissue and fascia creating a single muscle.

That protective covering of fascia and connective tissue is then what creates the tendons that attach the muscle to bone (one tendon on each side). In medical terminology, the point where muscle becomes tendon is called the musculotendinous junction.

So why are muscles made up of groups of muscle fibers versus one big muscle fiber that does it all?

Things are arranged this way so that we can modulate our efforts.

For easy tasks, we may only require a few groups to contract. For harder, maximum efforts, we will need every group of fibers working to its full ability.

This is known as recruitment and it is achieved by the nerves that supply the muscle. Messages from our brain and reflexes allow us to contract our muscles and also allow us to relax them.

If a muscle is unable to adequately respond to / meet the demands of a task, it can become overloaded and tear under strain.

This can happen for a few reasons: The muscle contraction required to perform the movement may be more than the muscle can generate. There was not enough time to fully recruit the muscle fibers. Restrictions in the muscle itself (mobility, strength, etc.,) prevented that full contraction.

Another reason is that muscles contract in two ways. The first is the normal shortening contraction (concentric). The second is a decelerating contraction where the muscle slowly lengthens to slow-down movements. In most muscuar injuries, the second type of contraction, an eccentric contraction is more commonly the culprit.

So What Is A Muscle Tear?

All muscle tears are technically muscle strains. Different words – same meaning. This occurs when muscle fibers are overloaded and fibres start to rupture under the force.

The percentage of muscle fibers involved and the severity of that tear are what determine the classification of the strain. Below you will find the three grades used by your doctor to diagnose the injury.

Grade I:

Mild strain. Only a small numbers of fibers (< 5%) are stretched or torn. While the injury may be painful, strength and mobility are unaffected and recovery is quicker. Grade I is “micro-tear” territory. The fibers have been pushed to the point of starting to tear but not completely.

Grade II:

Moderate strain. More fibers are involved and torn with a grade two. Grade II is a much larger injury and the symptoms reflect that. Symptoms include pain, swelling and bruising/discoloration. Strength and mobility are significantly diminished. Function is also impacted.

Grade III:

Complete rupture of a muscle. In a grade III tear, a muscle or its tendon are completely torn in two. This is a severe injury and includes considerable swelling, bruising, and pain. There is also a complete loss of muscle function with significant losses in strength and mobility. Due to the severity of this injury, you may also see visible defects in the muscle (gaps, dents, changes to the muscle shape itself) as the swelling subsides.

Where Do Tears Occur And How Long Does It Take to Heal?

Typically muscle injuries occur in one of three places:

  • Within the muscle belly itself (think meaty section of the muscle)
  • Where the tendon attaches to the bone
  • At the junction between the muscle and tendon (aka the musculotendinous junction). This is the most common area of the three.

Following the injury, there is an immediate period of inflammation and symptoms including pain, swelling, bruising/discoloration, and muscle cramps/spasms.

As the muscle heals, the damaged fibers will start to heal and scar tissue develops. Over time, the scar tissue will remodel and function will return, however, the muscle will never fully regenerate.

The site of injury will always contain scar tissue. This is why injured areas are prone to re-injury.

Recovery times will vary based on the severity of the strain. For a Grade I strain, full recovery is usually 2-3 weeks and athletes are able to resume activity when they are pain free. Grade II’s are more severe and take longer, averaging 2-3 months to fully heal the damage.

In the event of a complete rupture, medical care and often surgery are involved creating a a much longer recovery time.

In our next post, we will talk about what you can do on your own to speed up your recovery following one of these injuries.

About The Author 

My name is Leigh Boyle and I am a Doctor of Physical Therapy (DPT) and Certified Strength and Conditioning Specialist (CSCS). For the past 10 years, I was the co-owner of a private physical therapy practice in Southern New Hampshire. I am currently living and working out of Austin, Texas and enjoying a much needed break from the snow and cold. Professionally, I’ve treated injuries ranging from mild ankle sprains to advanced surgical reconstructions and most everything in between. I am certified in the Graston Technique and Active Release Therapy (ART), both of which are soft tissue mobilization techniques. I am also certified in functional taping applications and functional strenghtening. I’ve coached triathlon, cycling, and running teams on injury prevention and helped them develop off-season programs to focus on core strength and self body maintenance.


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