High-density surface electromyography (HDsEMG) is the use of four or more closely spaced electrodes to give insights into the spatial distribution of myoelectric excitation across a muscle.

While traditional bi-polar EMG gives an insight into the global activation strategies of the muscles, HDsEMG offers a window into the regional excitation and hence the recruitment and modulation of localized motor units within or between muscles.

HDsEMG technologies have several applications focusing on assessing how the regional excitation varies over the muscle. These applications include:

• Pain/Fatigue: Patients and athletes who can mitigate against these factors tend to redistribute load to different regions of the muscle during repetitive or sustained tasks. By using HDsEMG, it is possible to assess if the changes in regional activation occur which could minimize the effect of localized, persistent, and reoccurring pain or fatigue.
• Injury: Preferential recruitment of differing regions within a muscle has been suggested as an adaptability of the neuromuscular system to avoid potential injury from localized overload. As an example, participant-specific regional variations have been seen within hamstring muscles across the proximal and distal portions to aid performance and mitigate against injury inducing mechanisms.
• Disease: Within different disease populations, changes in regional distribution have been seen to signify maladaptation from the associated mechanical or neurological deficit. For instance, in stroke populations, paretic muscles have shown a reduction in overall motor unit numbers and more localized EMG activity resulting from de-innervation or muscle atrophy.
• Myoelectric Control: Multi-channel EMG sensors have been employed to provide a greater amount of input data for pattern recognition algorithms to create a more natural and intuitive human-machine interface. By using HDsEMG to decode the human motor intent, discrete patterns of regional muscle activation can be mapped to control outputs for the replication of specific movements of multi-functional prostheses with higher degrees of freedom.

HDsEMG is used to assess the spatial distribution of the myoelectric signal and variation in the EMG amplitude over time. From this, differing features can be extracted, such as the regional activation and the single motor unit activity.
Regional EMG amplitude differences can be interpreted as variations in the localized activation of muscle fibres in the specific regions.

Single motor unit recordings can extract information about the motor unit firing instances, firing rate and recruitment/de-recruitment thresholds to assess the effects of fatigue, neuromuscular disorders or injury and modulations brought about by training interventions.

For investigations into regional EMG amplitude differences and the spatial distribution of myoelectric signal, the Trigno Maize system provides the best solution.

When using the Trigno NeuroMap system, which includes the Trigno Galileo sensors and the NeuroMap software, investigations into single motor unit activity can be achieved during isometric and dynamic conditions using our advanced signal processing algorithms.

The HDsEMG technology provided by Delsys focuses on the wireless collection of high-fidelity EMG signals from dynamic activities, allowing you to capture unique insights from the neuromuscular system.

By re-engineering classical approaches to EMG sensors, all our innovative technologies are dry electrodes which allow for quick and easy application to the skin and high muscle conformity to maximize signal to noise ratios.

The Trigno Maize and Trigno Galileo sensors are built within the Trigno platform, meaning they can be used alongside our wide selection of compatible EMG technologies all from a single base system. Multiple Trigno Maize or Trigno Galileo sensors can be used synchronously to allow for multi-muscle investigations.