BodyWorks: EMG Neuromuscular Simulation
This tool creates EMG traces from action potentials passing down a nerve and along muscle fibres. You place two electrodes onto the muscle by dragging them with the mouse. The electrodes pick up the voltages from the action potentials passing along the muscle fibres. The voltages are displayed in the EMG trace at the bottom of the page.
The muscle can be “Tense” (100% of fibres get action potentials), “Medium” (50% of fibres get action potentials), or “Relaxed” (0% of fibres get action potentials).
You can view as “Time Fast”, “Time Medium”, or “Time Slow”, which changes the speed of the action potentials moving along the fibre. You can also use “Time Stopped” to stop the action potentials.
In “Realistic”, the muscle is split into different motor groups (one fibre per motor group), and the action potentials to each are realistic in that they are not synchronised. Action potentials join the muscle fibres near the middle, and propagate both ways. This is similar to what happens in real vertebrate muscles.
In “Simplified”, only one action potential moves through the nerve and muscle at a time. All action potentials move from left to right only.
Simulation by Dr Hugo Martay and Dr Jennifer Martay.
Approximations
- Thirty motor units, with one fibre each are shown in both the realistic and simplified models above. In real life, there are several hundred motor groups in the large muscles studied by EMG, and each motor group is made of several hundred fibres.
- The electrodes are able to almost target individual motor groups in the simulation above. With an electrode placed on the skin, this would be impossible in real life, and the signal would average over very many motor groups.
References
-
In the realistic model on this page, the signals are not synchronised,
which is broadly in line with the findings in the following paper:
https://journals.physiology.org/doi/full/10.1152/jn.00452.2015 Synchronization of motor unit firings: an epiphenomenon of firing rate characteristics not common inputs
Joshua C. Kline and Carlo J. De Luca (2016) -
In both models, the moderate activation of the muscles involves only a subset of the motor units / muscle fibres.
In the realistic model, at moderate activation, the firing rate is decreased for some motor units.
This reflects the findings shown in the following:
https://www.ncbi.nlm.nih.gov/books/NBK11021/figure/A1099/?report=objectonly Neuroscience. 2nd edition. Purves D, Augustine GJ, Fitzpatrick D, et al. (2001).
(After Monster and Chan (1977)) - Distance between electrodes: https://pubmed.ncbi.nlm.nih.gov/22169134/ (Inter-electrode spacing of surface EMG sensors: reduction of crosstalk contamination during voluntary contractions) by Carlo J De Luca et al.
Other Articles:
|
Experimental Flying GameFly around in a plane. Some physics, but mainly just playing with websockets. If you can get a friend to play at the same time, you should be able to shoot each other down. |
BodyWorks: Kinematics ToolA page with a javascript application where you can set body positions, calculate joint angles and animate human motion. |
|
|
Chernobyl SimulationAn attempt to simulate the normal running, and then accident of the Chernobyl nuclear reactor. |