Effects of intermittent cycle exercise on intramyocellular lipid use and recovery.

The purpose of this investigation was to compare intramyocellular lipid (IMCL) changes in skeletal muscle in nine moderately trained subjects after 45 min of interval cycling and through 1 h of recovery. The exercise session was continuous with alternating cycling intensity achieving 50 (3 min) and 110% (2 min) of ventilatory threshold. Spectra from the vastus lateralis were acquired before, immediately after, and 60 min following exercise using a 1.5 T Signa whole-body magnet (point-resolved spectroscopy sequence, echo time 60 ms, transverse relaxation time 2000 ms, 128 acquisitions, and 20 mm3 voxel). Immediately following exercise, IMCL concentration decreased 38% compared to pre-exercise levels (P < 0.05). Fitness level and baseline IMCL were not correlated with changes in IMCL following exercise (P > 0.05). In the 60-min recovery, IMCL was reduced 30% compared to baseline (P < 0.05) and did not recover. In contrast, a nonexercising control group showed no change in IMCL. Our results suggest that IMCL decreased significantly following 45 min of interval cycling, with little recovery in the hour following.