T-1 measurements of P-31 metabolites in resting and exercising human gastrocnemius/soleus muscle at 1.5 tesla

This study has measured the apparent P-31 T-1 times at 1.5 T in human gastr ocnemius/soleus muscle groups at rest, during exercise, and during recovery from a 90-sec submaximal plantar flexion exercise. T-1 times were measured with a 10-sec time resolution in 11 normally active volunteers using a sur face coil with a nine-point progressive saturation technique. A two-point: short repetition time technique was also used, Both techniques showed simil ar trends in the apparent T-11 times of ail the P-31 metabolites at rest, d uring exercise, and during recovery. For the nine-point progressive saturat ion technique, the apparent T-1 of PCr and beta-ATP decreased approximately 20% to a steadystate value (P = 0.027 and P = 0.004, respectively). The tw o-point short repetition time technique demonstrated a 10% reduction in the apparent T-1 of PCr and beta-ATP, Both techniques demonstrated an apparent T-1 increase of 58% for inorganic phosphate at the beginning of exercise ( P < 0.0001) and a return to resting Value during the 90-sec submaximal isom etric contraction. Neither technique showed any significant differences bet ween resting and exercising T-1 times of the alpha-ATP and gamma-ATP resona nces (P = 0.06 and P > 0.40, respectively). Magn Reson Med 41:486-494, 1999 , (C) 1999 Wiley-Liss, Inc.