CK concentrations typically react in a dose-response manner to exercise loadings. Our studies of combined endurance and strength loadings (steady state cycling performed before or after a mixed maximal and hypertrophic leg press protocol) typically led  increases in ck concentrations of only  20-30% at 24h post-loading. The increases you mentioned look like those observed after very fatiguing eccentric muscle actions (e.g. see work of Ken Nosaka). What kind of strenuous activity are you referring to?

thank you for the answer. The subjects report different kinds of activities related to work (building up a framework or stage) or sport (running, climbing, cycling). Maximal CK elevation I recently observed was 45.000 U/L (Ref R 0-171 U/L). Yet, two days later it decreased on 9.800. This male subject reported climbing. 

Thanks for the clarification. Given that in these tasks a large muscle mass is involved and both concentric and eccentric muscle actions are performed over a prolonged time, to me these increases are reasonable. After very isolated eccentric contractions of the elbow flexors only (e.g. 30 repetitions at a velocity of 30deg/s over a range of motion of 90 degrees) CK concentrations may in extreme cases go up to 65000 U/L. The average following this kind of loading is rather someting like 7000-10000 U/L, though but the muscle mass involved is comparably small. Also, our data showed that in most cases CK levels remain elevated for at least 5 days and the peak may be observed only on day 4. Also, the magnitude of CK elevations may be depending on whether the subjects are accustomed to a certain activity or not. Studies of the "repeated bout effect" show that the same exercise performed for the second time even after multiple days or weeks leads to dramatically reduced elevations of CK concentrations.

Dear Max,

in my view your results are not suprising, as you might find increased CK levels after strenuous muscle activity as nicely pointed out above. Only recurrent high CK levels with sings of rhabdomyolysis might point to metabolic myopathy. Your investigation might be worthwhile however if you could link types and /or durance of muscle acitivity in healthy controls to CK levels thereafter- possibly dependent on their individual training status (atheletes versus untrained subjects).

Best, Wolf

Thank you Wolf. Interesting point to correlate CK levels to training Status. I will check if this is feasible. I was suprised by the extend of CK elevation due to physical activity.

BR

Max