Time-resolved 3D phase-contrast MRI can be applied to quantify muscle contraction. 3D coverage with sufficient spatiotemporal resolution (~3x3x5mm3, 160ms) can only be achieved by interleaved acquisitions during many repetitions of a motion task, resulting in long scan times (>10min). In this study we have developed an accelerated protocol, using k-space undersampling and compressed-sensing reconstruction, which was applied on the lower leg of 4 volunteers performing a foot plantar-dorsal flexion motion task. Muscle velocities during the motion cycle of fully-sampled and accelerated protocols were compared. Acceleration was successful up to 6.4X with comparable velocities, which confirmed the benefit of this approach.