Characterization of Lower Limb Muscle Activation Patterns during Walking and Running with Intravoxel Incoherent Motion MR Perfusion Imaging

Objectives: Specific muscle recruitment patterns during walking and running are not well understood. Local blood flow of skeletal muscles depends on the metabolic activity during muscle activation. The aim of this study was to characterize specific muscle activation during walking and running using the noninvasive magnetic resonance imaging (MRI) microvascular perfusion method intravoxel incoherent motion (IVIM).

Methods: The 3-T MR IVIM images of the lower extremities of eight healthy volunteers were acquired at rest and immediately after walking and running, respectively. For IVIM measurements, a transverse monopolar pulsed gradient echo planar imaging fat-saturated spin-echo sequence was used (nine b-values from 0 to 1,000 s/mm²). Anatomical transverse T1-weighted turbo spin-echo images were acquired at rest. Muscles of the pelvis, thigh, and lower leg were segmented. IVIM perfusion parameters f, D*, and fD* plus the diffusion coefficient D were calculated.

Results: When considering the mean of all muscles, the microvascular perfusion parameter fD* was significantly higher after running (2.18 ± 0.98 × 10⁻³ mm²/s; p < 0.001) and after walking (1.99 ± 0.80 × 10⁻³ mm²/s; p < 0.001) as compared with rest (1.65 ± 0.83 × 10⁻³ mm²/s). The perfusion increase was most pronounced at the lower leg muscles and at the foot muscles (p < 0.001). Thigh muscles showed an fD* decrease from walking to running (p < 0.05). Mean heart rates increased from rest to walking and running; the increase correlated significantly and negatively with the increase of microvascular muscle blood flow (p < 0.05).

Conclusion: Running causes a redistribution of blood flow toward the lower leg. Noninvasive quantitative IVIM MRI is able to detect and monitor physiologic and potentially pathologic microvascular muscle perfusion patterns.

Conflict of Interest: None declared.