From the Guidelines
CK levels should not be used as the sole indicator of muscle damage in athletes, as the relationship between CK activity and muscle damage is complex and influenced by various factors, including ethnicity, body composition, and exercise intensity. When interpreting CK levels, it is essential to consider the individual athlete's characteristics and the specific exercise or training program they are undergoing 1. The optimal time point to collect blood samples for CK measurement is also unclear, as CK levels may peak between 24 and 120 hours after exercise, depending on the exercise modality 1.
Some key points to consider when using CK as a biomarker include:
- CK levels can be influenced by factors such as ethnicity, with black individuals tend to have higher CK levels than South Asian and white individuals 1
- Body composition, including muscle mass, can also impact CK levels, with larger muscle mass potentially leading to higher CK activity 1
- Exercise intensity and modality can affect CK kinetics, with high-intensity exercise and eccentric contractions tend to result in higher CK levels 1
- The relationship between CK activity and muscle damage is not always clear, with some studies suggesting a poor correlation between the two 1
In terms of clinical application, CK levels above 3000 U·L−1 may be considered abnormal or pathological, potentially indicating an increased risk of acute kidney injury 1. However, it is crucial to interpret CK levels in the context of the individual athlete's characteristics and the specific exercise or training program they are undergoing.
The use of CK as a biomarker for managing workload in athletes is still a topic of debate, with some studies suggesting that CK levels can be used to individualize load or recovery 1. However, more research is needed to fully understand the relationship between CK activity and muscle damage, as well as the optimal methods for interpreting and applying CK measurements in athletic populations 1.
From the Research
Rhabdomyolysis and Creatine Kinase (CK)
- Rhabdomyolysis is a syndrome characterized by the release of intracellular elements after the destruction of skeletal muscle, often accompanied by muscle pain, weakness, and dark urine, associated with elevated creatine kinase (CK) 2.
- The causes of rhabdomyolysis are varied, including traumatic etiology, immobilization, sepsis, drugs, and alcohol, with CK values used for diagnosis and prognosis 2.
- Elevated CK levels can also be seen in exertional rhabdomyolysis, which can be severe and lead to acute kidney injury and require higher level care with organ support 3.
Diagnosis and Treatment
- Diagnosis of rhabdomyolysis is based on the presence of symptoms such as myalgia, weakness, and muscle swelling, along with a substantial rise in serum creatine kinase (CK) 3.
- Treatment of rhabdomyolysis is focused on early and intensive fluid therapy to avoid kidney complications, with the goal of preventing acute kidney injury 2, 4.
- Acetaminophen has been shown to inhibit hemoprotein-catalyzed lipid peroxidation and attenuate rhabdomyolysis-induced renal failure, suggesting potential therapeutic applications 5.
Creatine Kinase (CK) Response
- Serum CK has been proposed as an indicator of muscle damage due to its ease of identification and relatively low cost of assays to quantify it 6.
- However, there is great interindividual variability in serum CK, which complicates the assignment of reliable reference values for athletes, and factors such as training level, muscle groups involved, and gender can influence CK levels 6.