Muscle strains comprise up to 55% of all injuries sustained in sports (1). We, the Rehab Specialists and Strength and Conditioning Coaches, need to be doing better in the prevention of muscle strains, as most of these are avoidable (2). One question in particular is frequently asked, but poorly answered in the pursuit of successful rehab of muscle tears:
“Should I stretch a strained muscle?”
This blog aims to answer this question, while also outlining clear rehab guidelines to help clinicians create successful rehabilitation pathways for their patients.
For a more detailed look at muscle injuries, be sure to check out Dr Nicol van Dyk’s Masterclass on Optimal Loading of Muscle Injuries.
Before determining a course of action post-injury, we must first understand the injury mechanism:
Muscle tears occur when the force applied to the tissue generates greater stress or strain than the tissue can withstand. This damages the myofibrils (muscle fibers) as a result of rapid eccentric (lengthening) contractions, often during acceleration or deceleration movements (3).
To stretch a muscle strain would appear to repeat the mechanism of injury and increase the potential to further damage an already weakened area. Therefore, by acknowledging that strains occur through loading muscle fibers beyond their capacity, it allows us to determine that immediately stretching/loading again would likely be disadvantageous.
However, avoiding stretching long-term is not the best solution either. Before diving into rehab guidelines for muscle strains, we first need to understand how to classify the severity of the injury and be aware of the natural healing process.
Classifying Muscle Strains
Below is the well-known muscle strain classification system.
Muscle strains most commonly occur at the myotendinous junction (MTJ) when force is being transferred from the muscle to the tendon. While many believe this is the definitive location where the muscle meets the tendon, the MTJ actually tapers a lot less definitively and several MTJs converge within the muscle belly itself. This is known as the intramuscular tendon where the myofibrils attach to the tendon within the muscle itself, and is another location site for muscle strains (1).
Based on this information, the BJSM proposed a new clinical classification system for muscle injuries which identifies the specific injury location within the muscle. This distinction is necessary as we now know proximity of the tear to the bone typically lengthens rehab time. Therefore by utilizing both classifications together, we can more accurately gauge expected recovery. This is largely determined through the two biggest factors of location and number of muscle fibers damaged (4).
Finally, muscle strain recurrence rates are >30%, so it’s important that we educate our patients on how to best manage these injuries in both the short and long-term (5).
Muscle Tear Healing Phases (& Proposed Practical Application) (4)
Phase 1: Degeneration/Inflammation Phase
→ Rupture and necrosis (death) of the myofibers
→ Inflammatory response: formation of hematoma (swelling and clotting of blood within the muscle tissue)
- Avoid complete rest, ice and NSAIDs (6)
- Do no HARM (Heat, Alcohol, Running, Massage) (7)
Phase 2: Regeneration Phase
→ Phagocytosis of necrotic tissue
→ Satellite cell activation and proliferation
→ Myofibers regeneration
→ Scar tissue formation
- Commence mobilisation/loading as early as is practical to benefit the healing process and reduce scar tissue build up (7)
Phase 3: Remodeling Phase
→ Maturation of myofibers
→ Scar tissue reorganisation
→ Possible fibrosis
- Perform strengthening exercises (5, 8)
Irrespective of classification, all muscle strains go through this process. It is the speed at which this occurs which will change depending on the severity of injury. Once the location and severity is determined, the biggest question is: How do we use this classification to guide our rehabilitation?
Integration is key. This should be less about arbitrary timeframes and more about ensuring clients tick off the necessary rehab checkpoints in sequence prior to moving onto the next phase of rehabilitation.
Proposed Muscle Strain Rehab Pathway
Here is a proposed rehab protocol to follow after a muscle strain:
- Relative Rest + Early Mobilisation
- Reduce activity and avoid aggravating the strain
- Commence light active movements to promote active recovery (increases blood flow to the area)
- Rebuild Range of Motion
- Focus on increasing joint ranges with light active stretching
- Avoid passive stretching and excessive muscle elongation
- Increase Endurance
- Low intensity (load/resistance), higher volume (repetitions)
- Focus on increasing muscular endurance through concentric muscle contractions
- Increase Load
- Increase intensity (load/resistance), decrease volume
- Stress the affected muscle through strength training
- Increase Speed
- Higher velocity contractions
- End stage: return to maximal speed (this should include mimicking the mechanism of injury)
For more on criteria-based rehabilitation and return to play decision-making after muscle strains, see Dr Nicol van Dyk’s Masterclass on Optimal Loading of Muscle Injuries.
Reducing Re-Injury Rates
Exit criteria for rehabilitation will differ depending on whether the client’s goal is to return to function, training or performance, each of which require greater intensity than the last. Ultimately, rehab is not complete when our clients are pain-free or even when they return to pre-injury levels of function and strength. Rehab should continue until the structures involved are more resilient than pre-injury levels. This requires rehab to transition into strength and conditioning for ongoing maintenance (8).
Addressing Risk Factors
It is important to note that one single eccentric contraction, with enough rapid strain, can be enough to cause a mechanically-induced muscle tear, independent of other factors. Despite these purely mechanical instances, the large majority of muscle strains are multifactorial in nature. Identifying and addressing underlying risk factors is imperative if we are to successfully rehabilitate and prevent muscle strains effectively (9).
Muscles that are inherently more susceptible to tears are (8):
- Biarticular muscles (crossing two joints)
- Muscles contracting eccentrically
- Muscles with a higher percentage of fast twitch (Type II) fibers
Modifiable factors that play a role in the occurrence of muscle strains include (8):
- Inadequate warm-up
- Prior injury to the muscle or its associated joints (impeding typical movement patterns)
- Insufficient range of motion or flexibility
- Weak or fatigued muscles
- Poor recovery (nutrition, hydration, sleep)
- Reduced vascular perfusion (due to disease)
Muscle strains can seem simple to rehab at first. Using pain as a marker of process can be misleading as this typically subsides relatively quickly with little intervention, and we know that recurrence rates are high.
Therefore the proposed muscle strain rehab guidelines outlined in this blog attempt to assist clinicians in the successful treatment of muscle strains and move clients through a more complete rehabilitation process. As clinicians, it is our job to facilitate a full recovery beyond pre-injury levels to build more resilient individuals in the long-term.