In young adult men who engage in resistance training, changes in creatine kinase levels occur after four weeks of either heavy lifting with few repetitions or lighter lifting with many repetitions,...
Mechanism
Synthesis from 1 study
Heavy lifting tears tiny parts of muscle fibers, causing a protein called creatine kinase to spill into the blood. Light lifting with more reps doesn’t tear the fibers as much, so less of this protein shows up in the blood. The amount of tearing depends on how hard the muscles are pulled, not how...
Most probable mechanism
When muscles are pushed hard with heavy weights, the force tears tiny parts of the muscle fibers and their outer membranes, causing a protein called creatine kinase to leak out into the blood. When muscles are worked with lighter weights and more reps, less tearing happens, so less of this protein escapes into the blood.
High mechanical tension during resistance contractions physically disrupts sarcomeres and the sarcolemma of muscle fibers
Structural damage to the muscle cell membrane increases its permeability, allowing intracellular enzymes to escape into the bloodstream
Creatine kinase, released from damaged muscle cells, is detected in serum as a biomarker of muscle tissue disruption
Less supported by current evidence, but not ruled out
When muscles are worked repeatedly with light weights, buildup of waste products causes mild inflammation, which may slightly increase membrane permeability and allow some creatine kinase to leak out.
Prolonged muscle contractions lead to accumulation of metabolic byproducts such as lactate and hydrogen ions
Metabolite accumulation induces low-grade cellular stress and transient changes in membrane integrity
Minor membrane alterations permit limited leakage of intracellular enzymes, including creatine kinase
Evidence from Studies
Supporting (1)
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