How much can exercise raise creatine kinase level—and does it matter?
Exercise elevates CK level, but consider other factors, too
Although exercise is known to elevate CK, it produces a wide range of levels, based on a host of variables.3,10 Increases in CK are more pronounced in males, blacks, and untrained people; age doesn’t seem to be a factor.10,11 Higher-intensity, longer-duration, and weight-bearing exercise (eccentric muscular contractions and downhill running) cause the greatest rises in CK.10 Other influences include temperature, altitude, gravitational forces, noise, and vibration.
No studies firmly establish a normal range of CK elevation from moderate exercise; better data are available for extreme athletes, such as long-distance runners and triathletes. One study found that mean total CK elevations 24 hours after a marathon were 3322 IU/L (22.3 times baseline) for men and 946 IU/L (8.6 times baseline) for women.4 Another study showed that triathletes had a 12-fold mean increase in CK levels as long as 24 hours after the race.12
Eccentric exercises significantly raise CK
Exercise programs that include eccentric muscle contractions can result in significant serum CK elevations. One study followed 203 participants to evaluate the magnitude of CK elevation and the effect on renal function produced by exercise.3 After performing 50 maximal eccentric elbow flexor contractions, 55% of participants had CK elevations >2000 IU/L at 4 days after exercise; 25% had CK elevations >10,000 IU/L; 13% had levels >20,000 IU/L. None showed any evidence of renal compromise on clinical follow-up. Another study found significant increases in CK (approximate mean of 15,000 IU/L) after repetitive eccentric elbow flexor contractions in college-age males.13
Eccentric weight lifting and similar activities, like downhill running, may result in an increase in serum CK levels of 10 to 20 times normal, whereas other nonweight-bearing exercises and exercise involving no or minimal eccentric contractions, such as swimming and cycling, cause only nominal increases in serum CK.10
Recommendations
No formal guidelines from authoritative sources are available.
Acknowledgments
The opinions and assertions contained herein are the private views of the authors and not to be construed as official, or as reflecting the views of the US Air Force Medical Service or the US Air Force at large.
