Contributions of dynamic phosphorus-31 magnetic resonance spectroscopy to the analysis of muscle fiber distribution.
OBJECTIVE
In high-performance athletes, conclusions regarding the muscle fiber distribution were to be drawn from dynamic 31phosphorus magnetic resonance spectroscopy (31P MRS).


METHODS
Eleven volleyball players (V), eight bodybuilders (B), and 22 nonathletic volunteers (N) were examined by dynamic 31P MRS. During rest, exhaustive exercise, and recovery, respectively, up to 60 consecutive phosphorus spectra of the quadriceps muscle were acquired by "time series" in 36 s each. Two main spectroscopic approaches to the spectroscopic analysis of muscle fiber distribution were applied: evaluation of the ratio Pi/PCr at rest and the computer-assisted analysis of the Pi-peak at its exercise-induced line width maximum.


RESULTS
At rest, the bodybuilders showed a significant lower Pi/PCr (0.07 +/- 0.03), in comparison with the volleyball players (0.11 +/- 0.03) and the nonathletic volunteers (0.11 +/- 0.02). The computer-assisted analysis of the Pi-peak at its line width maximum revealed a significantly lower pH of both of the subpeaks in the bodybuilders [6.30 versus 6.37 (V) and 6.38 (N); 6.89 versus 6.92 (V, N)], whereas the volleyball players provided the largest proportion of oxidative muscle fibers (68%), compared to bodybuilders (64%) and nonathletic volunteers (59%). A correlation between the ratio Pi/PCr and the area of the subpeak with the high pH (representing oxidative fibers) could not be demonstrated.


CONCLUSIONS
Spectroscopic results during rest and exercise may be influenced by the muscle fiber distribution of the respective volunteer. The applied spectroscopic approaches to the analysis of muscle fiber composition are not compatible with each other; depending on the applied method, the classification of a muscle fiber as type I or type II fiber may change. The influence of physiologic factors like muscle fiber distribution on spectroscopic results has to be considered in the interpretation of pathological conditions.
Schunk
K
K
Department of Radiology, University Hospital Mainz, Federal Republic of Germany.
Losch
O
O
Kreitner
K F
KF
Kersjes
W
W
Schadmand-Fischer
S
S
Thelen
M
M
D000328:Adult; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010759:Phosphorus Isotopes
D010759:Phosphorus Isotopes; D010725:Phosphocreatine; D010744:Phosphoric Monoester Hydrolases; D010727:Phosphoric Diester Hydrolases