Researchers use enzyme levels to track the muscle damage caused by an intense workout. One such marker, creatine kinase, reliably elevates during the days after exercise. This change has led some to assume that muscle damage causes the release of this enzyme. But recent evidence suggests a far more complicated situation than expected.
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Learn About Creatine Kinase
Creatine kinase breaks down the creatine naturally circulating throughout your body. This process creates the chemical phosphocreatine. Your body uses this biochemical for backup power. When needed, phosphocreatine fuels intense movements lasting a few seconds.
Repeatedly doing bursts of movements cause increases in creatine kinase. Those motions also cause increases in muscle soreness. Both effects last for several days. This coincidence often causes people to link creatine kinase and muscle soreness. They think that one effect causes the other.
Yet this relationship breaks down in many situations. Post-exercise muscle soreness can last long after creatine kinase has returned to normal levels, and treatments designed to treat muscle soreness often do so without affecting creatine kinase.
Read more: What Is Creatine Kinase?
Know the Numbers
Many people also show elevations in creatine kinase without having any muscle-related symptoms, according to a 2016 paper in the Cleveland Clinic Journal of Medicine. The authors note that most labs consider 0 to 200 IU/L the normal range of creatine kinase. Yet 5 percent of women and 19 percent of men fall outside this range.
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Respect Individual Differences
The relationship between creatine kinase and muscle damage breaks down in other ways as well. People show wildly different levels of creatine kinase depending on their genetic background and current situation, according to a 2015 report in the Journal of Exercise Nutrition and Biochemistry. These individual differences make it hard to document a relationship between creatine kinase and muscle damage.
Understand Genetic Contributions
Some people have a genetic predisposition to respond to heavy exercise with elevations in creatine kinase. Other people don't show this response. The ACTN3 gene may mediate these responses. A 2017 report in the Biology of Sport tested this hypothesis in highly trained women and men.
These researchers grouped the endurance athletes into those with the ACTN3 gene and those without it. They then measured creatine kinase levels after an ultra-endurance event featuring at least six hours of climbing, trekking and biking. Compared to their baseline, all athletes had higher levels of creatine kinase immediately after performing. Volunteers with the ACTN3 gene had higher levels after the event than those not carrying the gene, but they didn't perform differently.
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Your Physique Affects the Data
Body composition also affects your creatine kinase response to exercise. For example, people with greater body fat have a bigger response. This finding suggests that losing weight should lower your creatine kinase response. A 2014 article in the International Journal of Medical Sciences explored this possibility using a treatment known to cause weight loss — vibration therapy — in an animal model.
The scientists exposed overweight mice to either whole-body vibration or no treatment for six weeks. Compared to no treatment, whole-body vibration caused a decrease in body weight. It also decreased circulating levels of creatine kinase.
Gender Differences Play a Role
Gender differences affect creatine kinase levels as well. The creatine kinase levels of women and men respond similarly to exercise, but they return to baseline more quickly in women. A 2017 paper in Antioxidants documented this effect during a test known to increase creatine kinase production — downhill running in adult subjects.
These researchers looked at the impact of 20 minutes of running. This activity triggered a massive release of creatine kinase in both women and men. It took 48 hours for the levels to return to baseline in the women, while 72 hours were needed for the men. Menstrual cycle phase didn't affect the results. Interestingly, both genders remained sore for 72 hours. The latter finding adds to the large database showing a dissociation between creatine kinase and muscle soreness.
Age Contributes as Well
Your enzyme levels typically show an age-related decrease. They decline as you get older. This change may affect your creatine kinase response to exercise. A 2013 report in BioMed Research International tested this hypothesis in three age groups of males: boys, younger adults and older adults.
Participants did an exercise known to trigger creatine kinase — drop jumps. Tests done immediately before and after the exercise showed that all participants had a large increase in creatine kinase. The younger adults showed the largest increase.
Keeping It in Check
These findings show a poor relationship between creatine kinase and muscle damage. Yet there are still reasons to keep your creatine kinase in check. Given individual differences, doctors recommend taking action if your creatine kinase levels exceed 300 IU/L. A serious medical condition called rhabdomyolysis can occur at 1,000 IU/L.
It's important not to self-diagnose or treat a medical condition. Please speak with a health care expert if you suspect elevations in creatine kinase. Such elevation can indicate a life-threatening disease like diabetes. A doctor or trainer can help you understand the testing and actions needed to manage high creatine kinase.
Read more: What Are the Dangers of High Muscle Enzymes?
Train to Lower Creatine Kinase
Getting fit offers you the best way to lower your creatine kinase response to exercise. Preparing your body for an upcoming workout will decrease your enzyme response. Trainers refer to this phenomenon as the repeated bout effect. A study in Frontiers in Physiology illustrates this effect in women and girls.
The subjects did single-side elbow flexion exercises on two occasions separated by 14 days. Each session triggered the release of creatine kinase, but the response was smaller after the second session. The age of the participants didn't affect the results.
The repeated bout effect causes changes throughout your whole body. For example, a 2018 report in Medicine and Science in Sports and Exercise showed that training one leg decreases the creatine kinase response in the other leg. This amazing finding suggests that many factors, including biochemical signaling, contribute to the repeated bout effect.
Supplement to Lower Creatine Kinase
Branched-chain amino acids, BCAA, have a well-deserved reputation for aiding recovery after exercise. Suppression of the creatine kinase response to exercise may mediate this effect. A 2018 article in the journal Nutrients explored this possibility in healthy, fit men.
These researchers randomly assigned the men to one of two conditions: BCAA or placebo. All participants did an intense series of leg squats in a test known to trigger creatine kinase and cause muscle soreness. Compared to the placebo group, the BCAA group showed lower levels of creatine kinase 48 hours after working out. They also had less muscle soreness 48 and 72 hours later.
Massage Helps Lower Creatine Kinase
Coaches have increasingly used massage to help their athletes recover from intense exercise. Scientists have documented the positive effects of massage, but the mechanism remains unknown. A 2016 report in the Journal of Sports Sciences tested the effects of massage on exercise-induced increases in creatine kinase and other markers of muscle damage in male bodybuilders.
Participants were placed in either the treatment or the control group. They then did knee-extension and knee-flexion exercises. This test caused increases in creatine kinase and muscle soreness. It also caused decreases in athletic ability such as jumping and agility.
The treatment group received a 30-minute massage after these assessments. Compared to the control group, this intervention decreased creatine kinase 48 and 72 hours after the resistance exercise. It also decreased muscle soreness and increased athletic performance within 24 hours.
- SelfHacked: Creatine Kinase: High & Low Levels + Normal Range
- Journal of Musculoskeletal and Neuronal Interactions: Creatine Kinase Response to Resistance Exercise
- Practical Neurology: How to Do It: Investigate Exertional Rhabdomyolysis (or Not)
- Cleveland Clinic Journal of Medicine: Approach to Asymptomatic Creatine Kinase Elevation
- Journal of Exercise Nutrition and Biochemistry: Relationship of Creatine Kinase Variability With Body Composition and Muscle Damage Markers Following Eccentric Muscle Contractions
- Biology of Sport: Greater Muscle Damage in Athletes With ACTN3 R577X (RS1815739) Gene Polymorphism After an Ultra-Endurance Race
- International Journal of Environmental Research and Public Health: High Body Mass Index Is Associated With the Extent of Muscle Damage After Eccentric Exercise
- Antioxidants: Effect of Gender and Menstrual Phase on Serum Creatine Kinase Activity and Muscle Soreness Following Downhill Running
- Frontiers in Physiology: An Evidence-Based Approach for Choosing Post-Exercise Recovery Techniques to Reduce Markers of Muscle Damage, Soreness, Fatigue, and Inflammation
- Journal of Physiological Sciences: Aging-Induced Changes in Sex-Steroidogenic Enzymes and Sex-Steroid Receptors in the Cortex, Hypothalamus and Cerebellum
- BioMed Research International: Repeated Bout Effect Was More Expressed in Young Adult Males Than in Elderly Males and Boys
- Muscle and Nerve: Asymptomatic/Pauci‐Symptomatic Creatine Kinase Elevations (HyperCKemia)
- Critical Care: Beyond Muscle Destruction
- Frontiers in Physiology: Influence of Maturation Status on Eccentric Exercise-induced Muscle Damage and the Repeated Bout Effect in Females
- Medicine and Science in Sports and Exercise: Contralateral Repeated Bout Effect of the Knee Flexors
- Exercise and Sport Sciences Reviews: Mechanisms and Mediators of the Skeletal Muscle Repeated Bout Effect
- Applied Physiology, Nutrition and Metabolism: The Effects of Acute Branched-Chain Amino Acid Supplementation on Recovery From a Single Bout of Hypertrophy Exercise in Resistance-Trained Athletes
- Nutrients: Effect of Branched-Chain Amino Acid Supplementation on Recovery Following Acute Eccentric Exercise
- Sports Medicine: Massage and Performance Recovery
- Journal of Sports Sciences: Efficacy of Massage on Muscle Soreness, Perceived Recovery, Physiological Restoration and Physical Performance in Male Bodybuilders
- Journal of Applied Physiology: Muscle Damage and Inflammation During Recovery From Exercise
- Journal of Physical Therapy Science: Effect of Pulsating Electrostatic Field Application on the Development of Delayed Onset of Muscle Soreness (DOMS) Symptoms After Eccentric Exercis