Weight Training and Creatine Kinase (CK) Levels: A Literature Review

The Creatine Kinase (CK) is a blood marker commonly used to assess exercise induced muscle damage. However, little attention has been given for its use as an index of recovery and adaptation after weight training sessions. In this review, studies that measured the CK after single bouts of typical gym and fitness studios exercises were summarized, while eccentric actions or aerobic (endurance) studies were excluded. At a second step long term studies (greater thanfour weeks duration, or 1-2 weeks for overreaching) were used to estimate CK levels that could result in increase or decrease of performance (strength or hypertrophy). The analysis of this review showed that CK levels peaked after one to three days at mean levels of 2.5 (quads), 3.5 (whole body) or 4.5 (biceps) times the pre-exercise (base) levels. The variability though was very high and one more standard deviation brought these numbers to 5.5 times the base levels or 900 U/L. The long term studies showed that at CK levels greater than550 U/L (3.5 times the base levels), the performance tended to be stable or decrease. The main message of this review is that CK levels should be measured two to three days after the last training session and should be kept