[Dynamic 31-phosphorus magnetic resonance spectroscopy of the m. quadriceps: the effect of sex and age on the spectroscopic parameters].

PURPOSE

31P-MRS is used to assess the influence of sex und age on quadriceps muscle metabolism before and after exercise.

MATERIALS AND METHODS

32 healthy volunteers (15 women, 17 men, mean age: 38 +/- 17 yrs.) were examined by dynamic phosphorus-31 (31P) magnetic resonance spectroscopy (MRS). In the magnet, the quadriceps muscle was stressed by an isometric und an isotonic form of exercise until exhaustion, respectively.

RESULTS

Resting conditions: With increasing subjects' age, the ratio beta-adenosine triphosphate/total phosphate decreased (r = -0.37; p = 0.02). With increasing subjects' age, the ratios inorganic phosphate/phosphocreatine (r = 0.79; p = 5 x 10(-8), phosphomonoester/beta-adenosine triphosphate (r = 0.74; p = 10(-6) and phosphodiester/beta-adenosine triphosphate (r = 0.62; p = 10(-4) increased. The pH was the only one of the evaluated spectroscopic parameters which showed a sex-dependence: Female subjects had a significantly lower pH (7.03 +/- 0.02) than male subjects (7.05 +/- 0.03; p = 0.01). Exercise: With increasing age, the maxima of inorganic phosphate/phosphocreatine were less extreme during both of the exercises (r = -0.42; p = 0.0005). Likewise, the exercise-induced acidosis was less severe with increasing age (r = 0.53; p = 6 x 10(-6). After the end of the exercise, the times of half recovery of inorganic phosphate/phosphocreatine and the pH correlated neither with the subjects' age nor with sex or cross-sectional areas of the quadriceps muscle.

CONCLUSION

Sex and age of volunteers affect spectroscopic results. This influence had to be considered in the interpretation of spectroscopic studies.