Creatine supplementation - Part II: in vivo magnetic resonance spectroscopy

Purpose: Our purpose was to study effects of creatine (Cr) supplementation on muscle metabolites noninvasively by means of magnetic resonance spectros copy (MRS) before and after supplementation with Cr or placebo. Methods: H-1-MRS was used in a comprehensive, double-blind, cross-over stud y in 10 volunteers to measure Cr in m. tibialis anterior and m. rectus femo ris at rest. PCr/ATP was observed in m. quadriceps femoris by P-3)-MRS at r est and after exercise. Results: A significant increase in total Cr was observed with Cr intake in m. tibialis anterior (+9.6 +/- 1.7%, P = 0.001) and in m. rectus femoris (18.0 +/- 1.8%, P < 0.001). PCr/ATP showed a significant increase (+23.9 +/- 2.3%, P < 0.001) in m. quadriceps femoris at rest with Cr supplementation. Post-Cr supplementation recovery rates from exercise were significantly lo wer (k = 0.029 s(-1), P < 0.01) compared with postplacebo consumption (k - 0.033 s(-1)) and presupplementation (k = 0.037 s(-1)). However, higher leve ls of PCr/ATP at rest compensate for this reduction of the recovery rate af ter Cr supplementation. The increase of PCr/ATP determined by P-31-MRS corr elates with the increase of Cr observed by H-1-MRS (r = 0.824, P < 0.001). Conclusion: Noninvasive observation of Cr and PCr after Cr supplementation shows an increase in a muscle specific manner. Higher preexercise levels of PCr/ATP at rest compensate for significantly slower recovery rates of PCr/ ATP after Cr supplementation.