The consequences of a single bout of heavy eccentric exercise with and without repeated
concentric exercises on MRI images, serum CK levels and markers of inflammation were
studied. Two groups (ECC and ECCON), each consisting of 18 male volunteers, performed
70 eccentic contractions of the quadriceps femoris muscle. The study group (ECCON)
performed additional concentric contractions on a dynamometer (Cybex II+) one day
before and two hours, 1,2,3,6 and 9 days after eccentric loading. Serum levels of
creatine kinase (CK) were examined as a function of time, and correlated with measurements
of magnetic resonance imaging (MRI) of the involved muscle groups. T2-weighted images
of the thigh muscles were studied. Serum C-reactive protein, complement factors C3c
and C4, haptoglobin and transferrin were measured as markers of inflammation. Additional
concentric contractions (ECCON group) significantly increased CK, compared to the
ECC group. However, it had no apparent effect on MRI signal intensity changes, which
were of equal magnitude in the loaded vastus intermedius and deep parts of the vastus
lateralis in both groups. Likewise, the serum markers of inflammation of the exercised
muscles appeared to be absent. Based on MRI-images, additional concentric contractions
had no statistically significant effect on muscle damage and breakdown of connective
tissue. The five-fold increase in CK in the ECCON group could be a reflection of "massaging
out" of the CK from the muscles into the circulation by additional concentric exercises.
However, it could also be an indication for a superior sensitivity of assessing muscle
fiber damage in comparison to the MRI.
Key words
Eccentric exercise - concentric exercise - creatine kinase - magnetic resonance imaging
- inflammatory responses
