Surface EMG decomposition: a new tool for evaluating muscle function

Abstract

1. Introduction
Surface electromyography (sEMG) has been used over many years to give an indication of the level and timing of muscle activations during static and dynamic tasks, but these methods do not offer sufficient detail to determine individual motor unit (MU) behaviour. The development of decomposition EMG (dEMG) techniques have the potential to provide new insights in how the neuromuscular system controls movement. The recording of MU behaviour has previously been restricted to isometric tasks [1, 2, 3], but it is now possible to decompose cyclic dynamic contractions [4]. Despite this now being possible only a few studies have explored the differences in MU behaviour during concentric and eccentric muscle contractions during different movement tasks.
2. Materials and methods
This talk will consider the methods of data collection using dEMG and inertial measurement unit (IMU) sensors to quantify MU behavior during different functional and rehabilitation tasks. This will consider the effect of speed, load and phase of movement. Data on MU behavior will be presented on Vastus Medialis (VM) and Vastus Lateralis (VL) during squatting and leg raise tasks at different loads and speeds, and Peroneus Longus (PL) during standing balance tasks under different surface
conditions in individuals with and without ankle instability.
3. Results
Significant differences in MU behaviour can be seen between different speeds of movement, loads and between the concentric and eccentric phases. Increases in speed are associated with greater MU firing rates, whereas increases in load are associated with greater MU firing rates and the recruitment of larger MUs, with the concentric phase showing higher firing rates than the eccentric. The standing balance stability tests revealed marked differences between those with and without ankle instability, with greater firing rates when these are performed on an unstable surface.
4. Discussion
The ability to conduct surface dEMG signal decomposition during dynamic muscle activations is a recent technological development. The changes in MU behaviour; including firing rates and MU amplitudes, could help our understanding on how load, speed and balance are controlled by the central nervous 1. Introduction Surface electromyography (sEMG) has been used over many years to give an indication of the level and timing of muscle activations during static and dynamic tasks, but these methods do not offer sufficient detail to determine individual motor unit (MU) behaviour. The development of
decomposition EMG (dEMG) techniques have the potential to provide new insights in how the neuromuscular system controls movement. The recording of MU behaviour has previously been restricted to isometric tasks [1, 2, 3], but it is now possible to decompose cyclic dynamic contractions [4]. Despite this now being possible only a few studies have explored the differences in MU behaviour during concentric and eccentric muscle contractions during different movement tasks.
2. Materials and methods
This talk will consider the methods of data collection using dEMG and inertial measurement unit (IMU) sensors to quantify MU behavior during different functional and rehabilitation tasks. This will consider the effect of speed, load and phase of movement. Data on MU behavior will be presented on Vastus Medialis (VM) and Vastus Lateralis (VL) during squatting and leg raise tasks at different loads and speeds, and Peroneus Longus (PL) during standing balance tasks under different surface
conditions in individuals with and without ankle instability.
3. Results
Significant differences in MU behaviour can be seen between different speeds of movement, loads and between the concentric and eccentric phases. Increases in speed are associated with greater MU firing rates, whereas increases in load are associated with greater MU firing rates and the recruitment of larger MUs, with the concentric phase showing higher firing rates than the eccentric. The standing balance stability tests revealed marked differences between those with and without ankle instability, with greater firing rates when these are performed on an unstable surface.
4. Discussion
The ability to conduct surface dEMG signal decomposition during dynamic muscle activations is a recent technological development. The changes in MU behaviour; including firing rates and MU amplitudes, could help our understanding on how load, speed and balance are controlled by the central nervous system, and this is certainly an area worthy of further study.