Magnetic resonance imaging evaluation of cooling on blood flow and oedema in skeletal muscles after exercise

This study assessed the effects of cooling on blood flow and intramuscular water content in human skeletal muscles after exercise using magnetic resonance imaging. In six male subjects, their legs were randomly assigned to be control or to be cooled. All subjects performed ankle dorsiflexion exercise inside an imaging magnet and after exercise, an ice bag was placed on the ankle dorsiflexors of the cooled leg. Flow-sensitive images, which reflect both perfusion and intramuscular water, were obtained before and up to 270 s post-exercise at 30-s intervals. The flow-sensitive alternating inversion recovery (FAIR) images, which extract only the perfusion change, were also obtained. Signal intensity (SI) in the ankle dorsiflexors was estimated before and after exercise in both flow-sensitive and FAIR images. On the flow-sensitive images, the control leg increased SI 30–270 s after exercise (P<0.05), but the cooled leg showed no significant change. On the FAIR images, the control leg increased SI 30–270 s post-exercise (P<0.05), while the cooled leg increased SI 30–150 s and 210 s after exercise (P<0.05). The findings suggest that cooling attenuates the perfusion elevation and prevents the oedema formation in skeletal muscle immediately after exercise.