Neuromuscular electrostimulation (NMES) is a technique used in the clinical and training fields to increase the strength of a muscle group.The recent use of wide-pulse (WP) stimulations allows, in addition to the direct activation of the muscle fibers, the use of sensory pathways. This more global solicitation of the neuromuscular system (i.e. information going back to the spinal cord and even to the brain) prejudges more nervous adaptations and therefore a greater functional benefit. The first aim of this study is to evaluate and compare the force gains induced by 2 NMES training programs (CONV, WP) applied on knee extensors in healthy subjects for 6 weeks.The second aim is to understand the neuromuscular adaptations involved in these gains, as well as the functional benefit resulting from these improvements.
Neuromuscular electrostimulation (NMES) is a technique used in the clinical and training fields to increase the strength of a muscle group. The conventional (CONV) parameters of NMES induces a direct activation of the muscle fibers located close to the stimulation electrodes. This means that the neuromuscular system is not fully solicited, which limits its adaptation. The recent use of wide-pulse (WP) stimulations allows, in addition to the direct activation of the muscle fibers, the use of sensory pathways. This more global solicitation of the neuromuscular system (i.e. information going back to the spinal cord and even to the brain) prejudges more nervous adaptations and therefore a greater functional benefit. The first aim of this study is to evaluate and compare the force gains induced by 2 NMES training programs (CONV, WP) applied on knee extensors in healthy subjects for 6 weeks. The second aim is to understand the neuromuscular adaptations involved in these gains, as well as the functional benefit resulting from these improvements. To consolidate the benefit of NMES programs, a control (CONT) modality is used as a reference and is representative of a sedentary behaviour regularly observed in our populations. The CONV modality allows us to compare with the current clinical application and the majority of the literature on the adaptations induced by NMES training. Finally, the WP modality aims to assess the possible benefits linked to the use of wide-pulses during the application of NMES. A clinical transfer will then be envisaged to confirm the interest and benefits of this type of program. We hypothesise that nervous adaptations will be increased by the use of WP NMES, leading to greater gains in strength and functional benefits than with CONV NMES.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
39
The WP NMES program consists of electrical stimulation trains of 1000 symmetrical biphasic pulses (1 ms, 100 Hz). The duration of a train is of 10 s and the rest between trains is of 30 s. A WP NMES session includes 30 evoked contractions. The stimulation intensity is monitored online and adjusted to the highest tolerable by the subjects.During the stimulation, subjects are seated with the knee joint fixed a 60° angle. Three self-adhesive electrodes are placed over the right thigh. The positive electrodes, measuring 25 cm² (5 x 5 cm), are placed as close as possible to the motor point of the vastus lateralis and vastus medialis muscles. The negative electrode, measuring 50 cm² (10 x 5 cm), is placed 5-7 cm below the inguinal ligament. Electrical stimulations are delivered by a stimulator BioStim (Mazet Santé).
The CONV NMES program consists of electrical stimulation trains of 500 symmetrical biphasic pulses (0.2 ms, 50 Hz). The duration of a train is of 10 s and the rest between trains is of 30 s (duty cycle: 1/3). A WP NMES session includes 30 evoked contractions. The stimulation intensity is monitored online and adjusted to the highest tolerable by the subjects. During the stimulation, subjects are seated with the knee joint fixed a 60° angle. Three self-adhesive electrodes are placed over the right thigh. The positive electrodes, measuring 25 cm² (5 x 5 cm), are placed as close as possible to the motor point of the vastus lateralis and vastus medialis muscles. The negative electrode, measuring 50 cm² (10 x 5 cm), is placed 5-7 cm below the inguinal ligament. Electrical stimulations are delivered by a stimulator BioStim (Mazet Santé).
Control (CONT) modality is used as a reference and is representative of a sedentary behaviour regularly observed in our populations.
CHU de Saint-Etienne
Saint-Etienne, France
Maximal voluntary contraction (MVC) of the knee extensor muscle measurement
Maximal isometric force (maximal voluntary contraction, MVC) of the knee extensor muscle
Time frame: week 6
Voluntary activation measurement (%)
The level of voluntary activation will be determined by the force increment obtained following stimulation performed during a condition of the muscle in a state of maximum contraction.
Time frame: week 6
Voluntary activation measurement (%)
The level of voluntary activation will be determined by the force increment obtained following stimulation performed during a condition of the muscle in a state of maximum contraction.
Time frame: week 12
Cortico-spinal excitability measurement
The quantification of cortico-spinal excitability (i.e. motor evoked potentials, in mV) will be evaluated by recording the electromyographic responses (surface EMG) evoked by transcranial magnetic stimulation
Time frame: week 6
Cortico-spinal excitability measurement
The quantification of cortico-spinal excitability (i.e. motor evoked potentials, in mV) will be evaluated by recording the electromyographic responses (surface EMG) evoked by transcranial magnetic stimulation
Time frame: week 12
Spinal excitability measurement
The quantification of spinal excitability (i.e. spinal reflex, in mV) will be evaluated by recording the EMG responses evoked by electrical stimulation in the lumbar vertebrae. The quantification of spinal excitability (i.e. spinal reflex, in mV) will be evaluated by recording the EMG responses evoked by electrical stimulation in the lumbar vertebrae.
Time frame: week 6
Spinal excitability measurement
The quantification of spinal excitability (i.e. spinal reflex, in mV) will be evaluated by recording the EMG responses evoked by electrical stimulation in the lumbar vertebrae. The quantification of spinal excitability (i.e. spinal reflex, in mV) will be evaluated by recording the EMG responses evoked by electrical stimulation in the lumbar vertebrae.
Time frame: week 12
Muscular endurance measurement
Muscle endurance (number of contractions performed before failure) will be assessed during a fatigue protocol consisting of performing quadriceps muscle contractions at incremental strength levels.
Time frame: week 6
Muscular endurance measurement
Muscle endurance (number of contractions performed before failure) will be assessed during a fatigue protocol consisting of performing quadriceps muscle contractions at incremental strength levels.
Time frame: week 12
Jump performances measurement
The performance of jumps (height, in cm; length, in cm) will be evaluated during various tests of vertical (Squat Jump and Counter Movement Jump) and horizontal (Single Hop and Triple Hop) jumps.
Time frame: week 6
Jump performances measurement
The performance of jumps (height, in cm; length, in cm) will be evaluated during various tests of vertical (Squat Jump and Counter Movement Jump) and horizontal (Single Hop and Triple Hop) jumps.
Time frame: week 12
Postural balance performances measurement
The postural balance performance (displacement of the center of pressure, in mm) will be evaluated during a unipodal postural balance test performed on a force platform.
Time frame: week 6
Postural balance performances measurement
The postural balance performance (displacement of the center of pressure, in mm) will be evaluated during a unipodal postural balance test performed on a force platform.
Time frame: week 12
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