Early assessment of exercise induced skeletal muscle injury using plasma fatty acid binding protein.

OBJECTIVE: To test whether fatty acid binding protein (FABP) is a useful plasma marker for the early detection of exercise induced skeletal muscle injury in healthy subjects. METHODS: Plasma concentrations of FABP and myoglobin (Mb) were measured in six healthy physical education teacher trainees after 20 minutes of downhill running (16% incline; mean lactate 4 mmol/l; 70% (VO2MAX). Creatine kinase (CK) was measured for comparison. RESULTS: Significant increases were found in plasma FABP (mean peak level 50 micrograms/l), Mb (823 micrograms/l), and CK (491 U/l). Mb and FABP concentrations were already significantly elevated (p < 0.05) at 30 minutes, but CK not until two hours after exercise. Whereas Mb and FABP decreased to normal levels within 24 hours, CK activity remained elevated until 48 hours. The Mb to FABP ratio in plasma after exercise induced muscle injury was 15.0 (1.3) (mean (SEM)) (range 7.4-31.1), which is within the range of ratios calculated for skeletal muscle tissue contents of Mb and FABP, but different from the reported plasma ratio after myocardial injury (4- 6). CONCLUSIONS: After eccentric exercise induced muscle injury, plasma FABP and Mb increase and decrease more rapidly than CK, indicating that both FABP and Mb are more useful than CK for the early detection of such injuries and the monitoring of injury during repeated exercise bouts. In addition, the Mb to FABP ratio in the plasma identifies the type of muscle injured.