Urinary N-terminal fragment of titin: A surrogate marker of serum creatine kinase activity after exercise-induced severe muscle damage

J Sports Sci. 2021 Jul;39(13):1437-1444. doi: 10.1080/02640414.2021.1876329. Epub 2021 Mar 16.


We aimed to evaluate whether changes in the noninvasively assessed urinary N-terminal fragment of titin (U-titin) concentration may be associated with those of serum creatine kinase (CK) activity, transverse relaxation time (T2), maximal voluntary contraction (MVC) torque, range of motion (ROM), and muscle soreness, following high-intensity eccentric exercise. Twenty-eight healthy young men performed 30 maximal isokinetic (120°/s) eccentric elbow flexor contractions using an isokinetic dynamometer. U-titin concentration, serum CK activity, T2, MVC torque, ROM, and muscle soreness were measured before and after a maximum of 4 days. Both U-titin concentration and serum CK activity increased post-exercise in a similar manner, though the former elevated slightly earlier (p < 0.05). The peak values of log U-titin concentration following eccentric exercise were strongly correlated with those of log serum CK activity (r = 0.90, p < 0.05) and T2 (r = 0.84, p < 0.05). There were moderate correlations between peak values of U-titin concentration and those of MVC torque (r = 0.69, p < 0.05) and ROM decline rate (r = 0.45, p < 0.05). These results suggest that in healthy young men, the non-invasive marker, U-titin, may be used as a serum CK surrogate following exercise-induced severe muscle damage.

Keywords: Eccentric exercise; athlete; delayed-onset muscle soreness; magnetic resonance imaging; resistance training.

MeSH terms

  • Adult
  • Biomarkers / metabolism
  • Connectin / urine*
  • Creatine Kinase / blood*
  • Exercise / physiology*
  • Healthy Volunteers
  • Humans
  • Male
  • Muscle Strength / physiology*
  • Myalgia / metabolism*
  • Range of Motion, Articular / physiology
  • Upper Extremity


  • Biomarkers
  • Connectin
  • TTN protein, human
  • Creatine Kinase