Abstract
Neuromuscular electrical stimulation (NMES) is useful for muscle strengthening and for motor restoration of stroke patients. Using a portable ultrasound instrument, we developed an M-mode imaging protocol to visualize contractions elicited by NMES in the quadriceps muscle group. To quantify muscle activation, we performed digital image processing based on the Teager–Kaiser energy operator. The proposed method was applied for 35 voluntary patients (18 women and 17 men), of 63.8 ± 14.1 years and body mass index (BMI) 30.2 ± 6.70 kg/m2 (mean ± standard deviation). Biphasic, rectangular electric pulses of 350 µs duration were applied at two frequencies (60 Hz and 120 Hz), and ultrasound was used to assess the sensory threshold (ST) and motor threshold (MT) amplitude of the NMES signal. The MT was 23.4 ± 4.94 mA, whereas the MT to ST ratio was 2.69 ± 0.57. Linear regression analysis revealed that MT correlates poorly with body mass index (R2 = 0.004) or with the thickness of the subcutaneous adipose tissue layer that covers the treated muscle (R2 = 0.013). Our work suggests that ultrasound is suitable to visualize neuromuscular reactivity during electrotherapy. The proposed method can be used in the clinic, enabling the physiotherapist to establish personalized treatment parameters.
Highlights
Electrical stimulation for muscle strengthening is clinically useful in cases of immobilization, in early rehabilitation and in muscle reeducation [1]
If the muscle is at rest, more echogenic layers appear as bright horizontal stripes on the M-mode image; these are separated by dark stripes corresponding to less echogenic layers
The path of the US beam is crossed by tissue layers of various echogenicity, causing differences in brightness between successive pixels corresponding to a given depth [17]
Summary
Electrical stimulation for muscle strengthening is clinically useful in cases of immobilization, in early rehabilitation and in muscle reeducation [1]. Neuromuscular electrical stimulation (NMES) is especially useful when the patient is incapable of intense voluntary exercise [1]. NMES differs from voluntary exercise in three main ways [2]. Electrical stimulation recruits motor units in a reversed order because excitability is greater for motor neurons whose axons are larger in diameter. Electrical stimulation results in the firing of all motor neurons within the stimulated region. Sensory nerves are inevitably stimulated, as are pain fibers [2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
