Assessment of short-term physical loading of the back: is serum keratin sulfate an appropriate biomarker?

A prospective experimental study. To investigate the potential of serum keratan sulfate (KS) as an indicator of biochemical changes in intervertebral discs induced by physical loading of the back. By providing objective information on exposure and effects at the tissue level, biomarkers may enable us to improve our understanding of the intermediate steps between exposure to physical loading and the occurrence of back disorders. Serum KS has been proposed as a potential biomarker of the molecular changes in intervertebral discs that occur because of physical loading and are a potential cause of back disorders. Thirty-two nonimpaired men volunteers with a mean age of 22.5+/-2.3 years participated in the experimental condition, a manual lifting task, as well as in the control condition, lying on the back. Serum KS levels were measured immediately before and after both conditions, as well as 24 hours and 1 week later. No significant changes in serum KS levels were found after exposure to physical loading (mean SD serum KS before, 287.4+/-83.9 ng/mL; immediately after, 279.5+/-65.5 ng/mL; 24 hours after, 266.6+/-71.9 ng/mL; and 1 week after, 268.9+/-79.3 ng/mL), and no significant changes were found after lying on the back for 8 hours (mean+/-SD serum KS before, 273.0+/-94.3 ng/mL; immediately after, 261.6+/-68.9 ng/mL; 24 hours after, 277.3+/-68.9 ng/mL; and 1 week after, 274.5+/-68.5 ng/mL). These results indicate that the serum KS level is not suitable as a biomarker of the effects of short-term physical loading of the back induced by a manual lifting task