Simultaneous measurements of diffusion and transverse relaxation in exercising skeletal muscle.

The aim of this study was to compare proton T2 and apparent diffusion coefficient (ADC) variations induced by exercise in skeletal muscle, to provide some more information on the source of their variations. T2 and ADC were measured in the forearm flexor digitorum muscles in 12 healthy volunteers at rest and after an exercise, using a sequence allowing simultaneous measurements of both parameters. At rest, T2 was 30.6 +/- 1.8 ms (mean +/- 1 SD) and ADC was 1.82 +/- 0.11 x 10(-9) m2/s. With exercise, T2 varied by +2.8 +/- 12% (p < .001 vs. rest) and ADC varied by +12 +/- 3% (p < .001). The recovery of T2 after exercise was faster than that of ADC, with half-times of 7 +/- 2 min and of 15 +/- 8 min (p < .01), respectively. It is concluded that both T2 and ADC with exercise are probably different, T2 mostly reflecting changes in water content and ADC reflecting temperature variations.