Laser doppler myography (LDMi): A novel non-contact measurement method for the muscle activity

Abstract

Background and aims: Electromyography (EMG) is considered the gold-standard for the evaluation of muscle activity. Transversal and dimensional changes of the muscle, during muscle activity, generate vibrational phenomena which can be measured by Laser Doppler Vibrometry (LDVi). There is a relationship between muscle contraction and vibrational activity, therefore, some information on fundamental muscle parameters can be assessed without contact with LDVi. In this paper, we explore the possibility to relate the EMG signal causing the muscle contraction and the vibrational activity also measureable on the muscle. A novel non-contact measurement methodLaser Doppler myography (LDMi) -aiming to measure the vibrational behavior of muscle during contraction, is presented herein. Correlations with some parameters normally measured with EMG are reported. Materials and methods:The proposed method has been compared with standard superficial EMG (sEMG). Signals produced with sEMG and laser Doppler myography have been simultaneously acquired and processed to test correlations on a population of 20 healthy volunteers. Tests have been carried out on the flexor carpi ulnaris and the tibialis anterior muscles (left and right). Results: Results show that it is possible to measure: The timing of muscle activation (max differences: 440 ms), the amplitude of the signals acquired during activation respect to the signals during rest (S/N), the correlation between the S/N of the sEMG and LDMi signals at different levels of force (P> 0.89), and to assess muscle fatigue. Conclusions: LDMi is a valid measurement technique for the assessment of muscle activity and fatigue. It is a non-contact method and this characteristic could suggest its use together with low level laser therapy pre-, intra-and post-LLLT sessions to evaluate the efficacy and effects of the treatments without the need for invasive electrodes.

Sitting for Too Long, Moving Too Little: Regular Muscle Contractions Can Reduce Muscle Stiffness During Prolonged Periods of Chair-Sitting

“…However, considerably more work needs to be done to determine the contraction forces elicited by stimulation at the motor threshold level relative to maximum voluntary contractions. To quantify muscle contractions, a study similar to this one should be carried out using assessment techniques that are independent of electrical signals between the nerve and muscle, including laser doppler myography (Scalise et al, 2013 ; Casaccia et al, 2015 ), acoustic myography (Harrison et al, 2013 ; Harrison, 2018 ), or piezoresistive sensors (Esposito et al, 2018 ).…”

Control Methods for Transradial Prostheses Based on Remnant Muscle Activity and Its Relationship with Proprioceptive Feedback

“…These vibrations in the range of 5 to 100 Hz (with displacement amplitude up to 500 nm [ 109 ]) can be detected using microphones or low-mass accelerometers placed on the skin over the belly of the muscle. The vibration can also be measured with a non-contact approach, such as laser Doppler vibrometry [ 110 , 111 , 112 ]. As a control signal for externally powered prostheses, PMG possesses several advantages over myoelectric control, including robustness to changing skin impedance, moisture level, and does not require a reference signal that is common to electromyography [ 113 ].…”

Experimental study of self-oscillations of the trachea–larynx tract by laser doppler vibrometry

“…The LDV is a technique of measure which can detect a Doppler shift induced in a laser beam incident on a vibrating target, from which the velocity at which the target is vibrating is derived. Is is generally used in industrial settings for testing mechanical vibrations (see, e.g., [16]) and recently widely adopted for biomedical applications as a valid instrument for the assessment of the vibrations' behaviour of the human body [17][18][19][20]. With respect to the accelerometers, LDV are characterized by a wide dynamic range and accuracy and allow non-contact measurements up to a hundred meters, placing appropriate paint or reflecting stripes on the target [20][21][22][23].…”

“…Is is generally used in industrial settings for testing mechanical vibrations (see, e.g., [16]) and recently widely adopted for biomedical applications as a valid instrument for the assessment of the vibrations' behaviour of the human body [17][18][19][20]. With respect to the accelerometers, LDV are characterized by a wide dynamic range and accuracy and allow non-contact measurements up to a hundred meters, placing appropriate paint or reflecting stripes on the target [20][21][22][23]. The accelerometers, instead, have to be posed onto the structure and just perturbing the measures.…”