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Everything You Ever Wanted to Know About Muscle Strains
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Posted on: 12/11/2008
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Muscle injuries occur on a continuum (range) from mild to severe. They may present as delayed soreness a day or two after overuse. There could be a strain or even a muscle tear. In some cases, contact with another person or object can cause a contusion (bruise). In this article, orthopedic and sports medicine experts update information on two of those possible muscle problems: muscle strains and tears.
Understanding the treatment and management of muscle injuries requires a working knowlege of the anatomy and pathophysiology (what happens on a cellular level after injury). At the microscopic level, muscles are arranged in small units or bundles. They are surrounded by protective layers of tissue and satellite cells. The satellite cells are a type of stem cell that stand by in case of injury. They start the healing response when it's needed.
Muscle injury occurs when the muscle fibers are stretched too far, too fast. The strain or tear usually starts at the weakest part of the contractile unit. And the injury is most likely to occur during an eccentric contraction.
Eccentric contraction means the muscle is shortened or already contracted and is now lengthening. An example of this is the biceps muscle in the upper arm. Making a fist and bending your elbow as much as possible is a concentric contraction of the biceps muscle. Now, as you lower your hand and straighten the elbow, the biceps muscle is contracting eccentrically (lengthening or stretching out).
The weakest point of the muscle (where a strain is most likely to occur) is at the myotendinous junction. This is the transition zone between the muscle fibers and the tendon that attaches the muscle to the bone. The muscle is soft and pliable. The tendon is more like tough connective tissue and less resistant to sudden force.
Some muscles are more prone to injury because of the location or fiber type. For example, muscles that attach across two different joints are under increased force from different joint angles and movement. The hamstrings behind the thigh cross the hip and knee. The gastrocnemius (calf) muscle crosses the knee and ankle.These are two of the most commonly injured two-joint muscles.
Muscles are made up of two different types of fiber. You can see this most readily in a turkey or chicken by what we refer to as dark meat and white meat. Type I fibers have lots of endurance and resist fatigue (corresponds to what we think of as the white meat). Type II fibers (corresponds to what we think of as dark meat) have fast twitch fibers needed for speed and a quick response. It's the Type II fibers that are most vulnerable to a muscle stretch injury.
Once an injury has occurred, the body responds quickly. First, it mobilizes inflammatory cells and sends them to the area of injury. That's when we get pain, swelling, and a warmth or even hot feeling around the injured site. That's the acute phase (first 24 to 48 hours).
Then, the satellite cells are activated to create new muscle fibers. They help knit the torn area back together over the next six to eight weeks. In the last phase of muscle healing, the body spends some time remodeling the tissue.
Before treatment can begin, the physician must assess the injury and determine where is the patient in the healing process. A careful and thorough history and clinical exam are performed. The physician must rule out other problems such as a compartment syndrome, complete tendon tear, fractures, and infection. Imaging studies such as X-rays, ultrasound, or MRIs may be needed to confirm the diagnosis and perhaps show the extent of the injury.
An early or acute injury is usually managed with the RICE principle (rest, ice, compression, elevation). The goal is to reduce swelling and pain while restoring motion. Over-the-counter drugs such as Tylenol for pain relief or ibuprofen (nonsteroidal anti-inflammatory drug or NSAID) may be presecribed during the early phases of healing and recovery (seven to 10 days).
Long-term use of NSAIDs is no longer advised. Animal studies have shown that muscle force and function can be inhibited with prolonged NSAID use. These drugs may reduce the number of satellite cells available for tissue regeneration.
Resting the injured muscle is a good idea at first but long-term immobilization should be avoided. At first, the pain prevents movement. And during the acute phase, keeping the muscle and joints still helps protect the injured area from further damage. Scar tissue formation is also less likely if the strained muscle is given a short rest from a repeated contract-relax sequence.
Gentle movement should be resumed within 48 hours. Usually, this coincides with a natural decrease in pain and swelling. The task now is to regain motion and eventually full strength. For athletes, a physical therapist or athletic trainer can be very helpful during this phase of rehab and recovery. Sports experts recommend waiting to resume sports activity until the injured side has at least 80 per cent of strength when compared to the uninjured side.
Completing a full rehab program is an important step to avoiding reinjury. Preventing muscles strains from even occurring in the first place may be possible. Athletes with muscle strength imbalances appear to be at increased risk of a primary (first) muscle strain. That's one reason why a preseason screening program is advised for all competitive athletes.
For older adults who are active in sports or other physical activities, muscle atrophy and loss of tendon flexibility (contractility) are major risk factors. There's some evidence that stretching before physical activity may help prevent muscle strains. But this is currently a controversial area with some studies showing no preventive effect of stretching before exercising.
It makes sense that warm muscles are more flexible and possibly less prone to strain injury. Warm-up activities and stretching are still advised by some as part of strain injury prevention. Until further studies can clear up confusion around this subject, it can't hurt to include warm-ups in any training program and it may help.
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References:
Michele Pescasio, MD, et al. Clinical Management of Muscle Strains and Tears. In The Journal of Musculoskeletal Medicine. November 2008. vol. 25. No. 11. Pp. 526-532.
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*Disclaimer:*The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic. |
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