Changes in Urinary Titin N-terminal Fragment Concentration after Concentric and Eccentric Exercise

Area of Science:

• Exercise Physiology
• Biomarker Discovery
• Muscle Damage Research

Background:

• Exercise-induced muscle damage (EIMD) is a common outcome of physical exertion.
• Accurate and non-invasive biomarkers are needed to assess EIMD.
• Titin N-terminal fragment (UTF) is a protein fragment released during muscle damage.

Purpose of the Study:

• To compare urinary titin N-terminal fragment (UTF) concentrations after concentric versus eccentric exercise.
• To determine the specificity of UTF as a biomarker for EIMD.
• To investigate the relationship between exercise type and muscle damage markers.

Main Methods:

• Nine healthy men performed maximal effort concentric and eccentric elbow flexion exercises.
• Maximal voluntary isometric contraction (MVIC), muscle soreness (SOR), range of motion (ROM), serum creatine kinase (CK), and urinary UTF were measured for six days post-exercise.
• Workload was kept consistent between exercise types.

Main Results:

• Eccentric exercise led to significant increases in serum CK activity, MVIC, SOR, ROM, and urinary UTF concentration compared to concentric exercise.
• Despite identical workloads, eccentric exercise induced greater muscle damage and higher UTF levels.
• Urinary UTF concentration showed a marked increase following eccentric exercise.

Conclusions:

• Urinary titin N-terminal fragment (UTF) concentration is a sensitive indicator of exercise-induced muscle damage (EIMD).
• UTF demonstrates high specificity as a non-invasive biomarker for EIMD, particularly following eccentric contractions.
• This study supports the use of urinary UTF for monitoring muscle damage in response to exercise.