Measurement of human skeletal muscle oxidative capacity by 31P-MR spectroscopy: a cross-validation with in vitro measurements

Purpose:

To cross‐validate skeletal muscle oxidative capacity measured by ³¹P‐MR spectroscopy with in vitro measurements of oxidative capacity in mitochondria isolated from muscle biopsies of the same muscle group in 18 healthy adults.

Materials and Methods:

Oxidative capacity in vivo was determined from PCr recovery kinetics following a 30‐s maximal isometric knee extension. State 3 respiration was measured in isolated mitochondria using high‐resolution respirometry. A second cohort of 10 individuals underwent two ³¹P‐MRS testing sessions to assess the test–retest reproducibility of the method.

Results:

Overall, the in vivo and in vitro methods were well‐correlated (r = 0.66–0.72) and showed good agreement by Bland Altman plots. Excellent reproducibility was observed for the PCr recovery rate constant (CV = 4.6%; ICC = 0.85) and calculated oxidative capacity (CV = 3.4%; ICC = 0.83).

Conclusion:

These results indicate that ³¹P‐MRS corresponds well with gold‐standard in vitro measurements and is highly reproducible. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.