Fatigue and the Electromechanical Efficiency of the Vastus Medialis and Vastus Lateralis Muscles

Abstract

Context:The relationship between the amplitudes of the mechanomyographic (MMG) and electromyographic (EMG) signals has been used to examine the ''electromechanical efficiency'' (EME) of normal and diseased muscle. The EME may help us to better understand the neuromuscular relationship between the vastus medialis and vastus lateralis muscles.Objective: To examine the EME of the vastus medialis and vastus lateralis muscles during a fatiguing task.Design: Repeated-measures design. Setting: Research laboratory.Patients or Other Participants: Ten healthy males (age 5 23.2 6 1.2 years) with no history of knee injury.Intervention(s): Seventy-five consecutive, maximal concentric isokinetic leg extensions at a velocity of 1806/s.Main Outcomes Measure(s): Bipolar surface EMG electrodes were placed over the vastus medialis and vastus lateralis muscles, with an MMG contact sensor placed adjacent to the superior EMG electrode on each muscle. The MMG and EMG amplitude values (root mean squares) were calculated for each of the 75 repetitions and normalized to the highest value from the 75 repetitions. The EME was expressed as the ratio of the log-transformed normalized MMG amplitude to the normalized EMG amplitude. For each muscle, the linear relationship for the normalized-group mean EME was determined across the 75 repetitions.Results: Linear regression indicated decreases in torque (R 2 5 .96), vastus medialis EME (R 2 5 .73), and vastus lateralis EME (R 2 5.73). The slopes for the vastus medialis and vastus lateralis EME were not different (P . .10).Conclusions: The similarities in the fatigue-induced decreases in EME for the vastus medialis and vastus lateralis muscles suggested that symmetry was present between the muscles in the electric and mechanical responses to repeated, maximal muscle actions. The EME measurements may provide a unique insight into the influence of fatigue on the contractile properties of skeletal muscle, including alterations that occur to the intrinsic electric and mechanical components. The EME may be useful in assessing and quantifying clinically relevant asymmetries in vastus medialis and vastus lateralis muscle function in those with knee injuries.Key Words: mechanomyography, electromyography Key PointsN In healthy muscle, the electromechanical efficiency of the vastus medialis and vastus lateralis muscles decreased concurrently with decreased torque. Thus, as suggested by others, electromechanical efficiency may provide an index of changes in electromechanical coupling.N Electromechanical efficiency may offer insight into the influence of fatigue on skeletal muscle function and be a useful tool to assess and quantify clinically relevant asymmetries in vastus medialis and vastus lateralis muscle function in those with knee conditions.

Novel insights into skeletal muscle function by mechanomyography: from the laboratory to the field

“…These articles focused mainly on the modifications of MMG signal (in particular by calculating MMG RMS and MF or MPF) after isometric voluntary [2, 90, 92-95, 97, 100, 102] and electrically evoked contractions [16,17], or dynamic contractions [82,89,91,96,98]. With the only exception of Camic et al [89] and Orizio et al [2], increases in MMG amplitude accompanied by decreases in MMG signal frequency content were reported in all the Sport Sci Health other investigations under both isometric and dynamic conditions.…”

“…Eleven studies over twenty used an ACC to detect MMG signal [2,[16][17][18][89][90][91][92][93][94], seven used a PIZ [82,[95][96][97][98][99][100], and two utilized an MIC [101,102].…”

Correlation between spectral and temporal mechanomyography features during functional electrical stimulation

“…In voluntary contractions, Ebersole and Malek (2008) stated that the MMG RMS increases could be attributed to the recruitment of new motor units. Our results showed that along the time, with the application of electrical current, occurred a decrease in muscle oscillatory frequency (our results).…”

Correlation between mechanomyography features and passive movements in healthy and paraplegic subjects

“…RIAXIAL accelerometers are used to assess corporal balance and to measure the lateral oscillation during muscular contraction (or stretching) [1,2] in a technique defined as mechanomyography (MMG) [3]. MMG signals can be indicated as feedback in the control of myoelectrical prostheses [5,6] or neuroprostheses with functional electrical stimulation (FES) [4], using temporal and spectral features [7,8].…”