The Relationship Between Quadriceps Femoris Muscle Function and MRI-Derived Water Diffusion and Adipose Tissue Measurements in Young Healthy Males.

Abstract

Water diffusion and adipose tissue in a muscle can be evaluated by MRI. However, determining which quadriceps femoris muscle (QM) characteristics independently predict peak knee extension torque during maximum voluntary isometric contractions (MVICs), individual muscle activity during MVICs and sit-to-stand transitions is unknown. To determine which QM characteristics predict knee extension muscle strength and individual muscle activity. Prospective, cross-sectional. A total of 20 healthy males (aged 22-40 years) with a physical activity level <1 hour/week. 1.5-T, diffusion-weighted fast spin-echo echo-planar imaging and T1-weighted fast spin-echo sequences. The vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF), and vastus intermedius were segmented in a single axial diffusion-weighted image and T1-weighted image at the right mid-thigh region. λ1-3 and fractional anisotropy (FA), and the percentage of intramuscular adipose tissue (IMAT) were measured. The knee extension peak force during MVICs was measured by a dynamometer, and the torque was calculated at the peak force × length. The ratios of the individual muscle activity to the total muscle (VM, VL, and RF) during MVICs and sit-to-stand transitions were assessed using surface electromyography. Regression analysis was conducted to identify the predictors of peak knee extension torque and of individual muscle activity ratios. A P value < 0.05 was considered statistically significant. The RF λ1 significantly predicted the peak knee extension torque (β=-0.51). The IMAT percentage of the VM significantly predicted the VM muscle activity ratio during the MVIC and sit-to-stand transition (β=-0.82 and β=-0.61, respectively), whereas the ratio of the VM λ1 to the whole QM λ1 significantly predicted the VM muscle activity ratio during the sit-to-stand transitions (β=0.35 and β=0.46, respectively). The RF λ1 may allow to estimate peak knee extension muscle torque, and the VM IMAT and λ1 may predict muscle activity in youth. 3. Stage 3.