Dynamic P-31-MR-spectroscopy of the quadriceps muscle: Influrence of sex and age on spectroscopic results.

Purpose: P-31-MRS is used to assess the influence of sex und age on quadric eps muscle metabolism before and after exercise. Materials and Methods: 32 healthy volunteers (15 women, 17 men; mean age: 38 +/- 17 yrs.) were examin ed by dynamic phosphorus-31 (P-31) magnetic resonance spectroscopy (MRS). I n the magnet, the quadriceps muscle was stressed by an isometric und an iso tonic form of exercise until exhaustion, respectively. Results: Resting con ditions: With increasing subjects' age, the ratio beta-adenosine triphospha te/totat phosphate decreased (r = -0.37; p = 0.02). With increasing subject s' age, the ratios inorganic phosphate/phosphocreatine (r = 0.79; p = 5 x 1 0(-8)), phosphomonoester/beta-adenosine triphosphate (r = 0.74; p = 10(-6)) and phosphodiester/beta-adenosine triphosphate (r = 0.62; p = 10(-4)) incr eased. The pH was the only one of the evaluated spectroscopic parameters wh ich 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 les s extreme during both of the exercises (r = -0.42; p = 0.0005). Likewise, t he 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 area of the quadriceps mu scle. Conclusion: Sex and age of volunteers affect spectroscopic results. T his influence has to be considered in the interpretation of spectroscopic s tudies.