Coactivation pattern in human quadriceps during isokinetic knee-extension by muscle functional MRI

Abstract

We tested activation patterns of individual muscles and neuromuscular compartments (NMCs) of the quadriceps femoris (QF) during knee-extension exercises (KEE). Eight healthy men performed repetitive isokinetic KEE at 120 degrees s(-1). Before and after KEE, muscle functional magnetic resonance images of the thigh were taken to calculate transverse relaxation times (T2) for the individual muscles of the QF. In terms of exercised T2, a moderate correlation was observed between the rectus femoris (RF) and vastus medialis (VM) ( r=0.493, P<0.001), and between the vastus lateralis (VL) and VM ( r=0.347, P<0.01). Furthermore, a strong correlation was also observed between the vastus intermedius (VI) and VM ( r=0.719, P<0.0001), and between the VL and VI ( r=0.783, P<0.0001). There was a significant difference in T2 between the proximal and distal NMCs of the RF. We conclude that at least two strategies are applied for force production in the human QF: (1) coactivation of specific pairs of individual muscles and (2) regional-specific activation in NMCs in the RF.

Functional T2 Mapping of the Trunkal Muscle

“…Change in T2 after exercise is not enough to show the potential of increased vascular ‰ow and edematization. 4,[7][8][9] However, this result suggests that T2 changes are induced at least by the exercise. …”

“…The transverse relaxation time (T 2 ) of exercised muscle is greater than that of muscle at rest, [1][2][3] and Akima and associates proposed muscle functional magnetic resonance imaging (mfMRI) 4,5 to visualize the enhanced activity. However, its use with spin echo (SE) sequence to calculate T2 requires minutes of the acquisition time and is limited to the limbs.…”

T2 Mapping of Muscle Activity using Ultrafast Imaging

“…[11][12][13][14][15][16] For example, Adams and associates used shifts in contrast on MR images in an attempt to map regions of the thigh muscle stimulated by transcutaneous electromyostimulation (EMS). 11 Similarly, Akima's team tested the coactivation patterns of individual muscles and the neuromuscular compartments of the quadriceps femoris during knee-extension exercises.…”

“…11 Similarly, Akima's team tested the coactivation patterns of individual muscles and the neuromuscular compartments of the quadriceps femoris during knee-extension exercises. 14 In particular, they proposed muscle functional MR imaging (mfMRI) as a technique for visualizing muscle activity from T 2 changes. 14,16 However, mfMRI uses a spin-echo (SE) or multiple spin-echo (MSE) sequence to calculate T 2 , both of which require several minutes for acquisition.…”

“…14 In particular, they proposed muscle functional MR imaging (mfMRI) as a technique for visualizing muscle activity from T 2 changes. 14,16 However, mfMRI uses a spin-echo (SE) or multiple spin-echo (MSE) sequence to calculate T 2 , both of which require several minutes for acquisition. Unfortunately, the duration of conventional imaging techniques is restricted, so mfMRI can only be applied to the limbs.…”