Muscles, like other soft tissues in your body, are quite susceptible to damage. Trauma, infections, certain drugs or even strenuous exercise can all instigate damage to your muscles. Pain is a common indicator of muscle damage, but it is sometimes insufficient to establish a diagnosis. For this reason, certain biomarkers in the bloodstream, called creatine kinase, are often used to confirm damage to the muscles.
Function of Creatine Kinase
Creatine kinase, or CK, is a type of enzyme found in your muscles. CK aids in the production of phosphocreatine, a molecule utilized by your muscles for energy. CK is normally found in your muscles, but injury to the membrane surrounding the muscle can cause CK to leak into the bloodstream. CK actually exists as three separate forms: CK-MM, CK-MB and CK-BB. CK-MM is located primarily in the skeletal muscles, whereas CK-MB is localized to the heart and CK-BB is mostly found in the brain. For males over 18 years of age, normal levels of CK in the blood range anywhere from 52 to 336 units per L, or U/L. Normal levels of CK in females should fall between 38 and 176 U/L.
Causes of Elevated Creatine Kinase
Injuries to the skeletal muscles often trigger high levels of CK-MM. These muscles are the type that most commonly comes to mind when we hear the word muscle. These are the "voluntary" muscles that you are able to control -- for example, the biceps and triceps. Damage to these muscles can occur for various reasons, including muscular dystrophy, direct trauma, strenuous exercise, immobility, certain drugs, muscle injections, nerve conduction studies, muscle infection, seizures or surgery. Strenuous exercise frequently triggers a rise in CK that peaks 16 to 24 hours following a workout, then stays elevated for 72 hours before falling back to baseline. Those with muscle diseases typically experience chronically elevated CK-MM. In fact, those with Duchenne's muscular dystrophy may have levels that are 50 times greater than normal.
Branched Chain Amino Acids
Several studies suggest that amino acids may actually ameliorate CK levels after exercise. According to a study published in December 2007 in the "International Journal of Sport Nutrition and Exercise Metabolism," branched-chain amino acid, or BCAA, supplements may reduce CK levels after exercise as well as muscle damage and muscle soreness. The study found that consumption of a beverage containing 200 kilocalories of BCAA immediately before and 60 minutes into a workout reduced CK levels four, 24 and 48 hours after completion of exercise. These findings may be of particular benefit to those suffering from delayed onset muscle soreness after exercise.
Warning
One of the most common causes of elevated CK is a lack of oxygen to the heart muscle, known medically as a myocardial infarction or heart attack. According to Mayo Medical laboratories, CK levels peak two to 24 hours following a heart attack and then fall back to baseline after three to four days. Seek immediate medical attention if you have symptoms of a heart attack, such as chest pain, shortness of breath, jaw pain that radiates to your left arm or excessive perspiration. Since many of the causes of skeletal muscle damage can also be quite serious, it is also recommended that you contact your doctor if you experience severe or prolonged muscle pain or weakness.
References
- Muscular Dystrophy Association; Simply Stated . . . The Creatine Kinase Test; February 2000
- MedlinePlus; CPK Isoenzymes Test; David C. Dugdale III, M.D.; February 2011
- Mayo Medical Laboratories: Creatine Kinase (CK), Serum
- ChronoLab: Creatine Kinase (CK)
- "International Journal of Sport Nutrition and Exercise Metabolism"; Branched-Chain Amino Acid Supplementation and Indicators of Muscle Damage after Endurance Exercise; B.K. Greer, et al.; December 2007
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