Stimulation Sites and Fatigue Induced by Neuromuscular Electrical Stimulation in Healthy Individuals

NCT05605210 | Active Not Recruiting DMC

• 1 other identifier: 5.309.992
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

Neuromuscular electrical stimulation (NMES) is a tool used in training protocols and in clinical practice to prevent or attenuate atrophy and improve the ability to produce muscle strength in different populations. Although widely used, the effects of NMES can be limited by discomfort and early fatigue induced by electrical current. Previous studies have investigated alternatives to minimize muscle fatigue, reduce muscle discomfort and increase muscle performance. A measure adopted to reduce the NMES's deleterious effects is the choice of stimulation site. More specifically, muscle contractions can be evoked by applying electrical pulses to the trunk of peripheral nerves (nNMES) or terminal branches of the nerve at the muscle belly level (mNMES). There is evidence that the mNMES stimulates the more superficial motor units (MUs), while the deeper MUs of the muscle remain inactivated, or, to recruit them, an additional increase in current intensity and stimulation frequency may be required. On the other hand, in direct nerve stimulation (nNMES) both superficial and deep MUs are recruited regardless of NMES intensity. Based on these observations, a new application modality of NMES emerged, the intercalated nerve and muscle stimulation (iNMES). In this strategy, electrical pulses are intercalated or alternated between the mNMES and nNMES sites, intending to reduce the high frequencies at which the MUs are activated during NMES, recruiting both superficial and deep MUs, and reducing muscle fatigue during evoked contractions. Although iEENM is a promising strategy to potentiate the NMES effects, few studies have investigated the iNMES effects on neuromuscular fatigue, and the existing literature is solely focused on the analysis of the tibialis anterior muscle, limiting the findings' inferences for other muscles important for lower limb functionality (e.g., quadriceps femoris). Therefore, the objective of this study is to compare the effects of nNMES applied to the femoral nerve (FN-NMES), of mNMES applied to the rectus femoris' motor point (MP-NMES), and iNMES applied simultaneously to both sites (FNMP-NMES) on knee extensors' functional (muscle fatigue) and clinical (discomfort) parameters in healthy individuals, through a randomized clinical trial. Our study has three hypotheses. In our first hypothesis, muscle fatigue during an electrical stimulation protocol will be lower with the FNMP-NMES modality, followed by FN-NMES, and will be higher with MP-NMES. Thus, FNMP-NMES will present a smaller reduction in maximal voluntary isometric contractions (MVICs) immediately after the fatigue protocol, a smaller relative reduction between the final compared to the initial evoked torque, a greater number of contractions for the evoked torque to reduce 50% with respect to the initial torque during the NMES fatigue protocol, and a greater total work compared the FN-NMES and MP-NMES modalities. In our second hypothesis, low frequency (20 Hz) NMES will produce greater total work and less fatigability of the knee extensors (smaller reduction from pre to post MVIC, smaller percentage reduction at the final compared to the initial evoked torque, a greater number of contractions for the evoked torque to reduce 50% compared to the initial evoked torque, and greater total work) compared to a high stimulation frequency (100 Hz). Furthermore, the total work will be higher and the fatigability lower with FNMP-NMES, followed by FN-NMES, and finally MP-NMES, regardless of stimulation frequency. Finally, the third hypothesis is that discomfort will be less with FNMP-NMES, followed by FN-NMES, and finally MP-NMES, regardless of stimulation frequency.

Conditions

Fatigue

Keywords

Electrical stimulation; Fatigue

Outcome Measures

Primary Outcomes (10)

• Level of physical activity

  The level of physical activity (PA) of each subject will be assessed by the International Physical Activity Questionnaire (IPAQ).The scores will be assessed by calculating the metabolic equivalents (MET) for each activity level. Walking score will be achieved by the multiplication of 3.3 METs with the total walking duration in minutes in a week. Moderate physical activity scores will be achieved by the multiplication of 4.0 METs with the total moderate physical activity duration in minutes in a week. Vigorous physical activity scores will be achieved by the multiplication of 8.0 METs with the total vigorous physical activity duration in minutes in a week. Total physical activity MET-minutes/week will be obtained through sum of walking, moderate and vigorous MET minutes/week scores. Categorical Score will be classified into three levels of physical activity: low, moderate and high.

  The assessment will be performed before the introduction of the intervention.

• Thickness of the subcutaneous fat layer on the motor point and femoral nerve

  Corresponds to the amount of subcutaneous adipose tissue and will be evaluated by ultrasonography

  The assessment will be performed pre-intervention, that is, before each NMES protocol

• Maximum voluntary isometric contraction of the knee extensors

  Knee extensor maximal voluntary isometric contraction (MVIC) is an expression of the muscular strength, and will be evaluated by dynamometry.

  The assessment will be performed pre-intervention, that is, before each NMES protocol

• Current intensity required to evoke knee extensors' submaximal torque (20% MVIC)

  The amount or amplitude of electrical current (in milliamperes - mA) required to achieve a specific force (20% MVIC), and will be evaluated from the electrical stimulation device.

  The assessment will be performed pre-intervention, that is, before each NMES protocol

• Change from rest Evoked torque by supramaximal twitch at pre-intervention and immediately after the intervention

  Simple biphasic rectangular electrical pulses will be applied at a frequency of 1 Hz at a current intensity sufficient to generate a visible contraction of the knee extensors. From the identification of this motor threshold, the current intensity will be gradually increased until no subsequent increase in the evoked twitch torque is observed. Then, the current intensity will be increased by 10% in order to guarantee that the torque evoked by the twitch is supramaximal. The torque (Nm) evoked during the twitch will be determined by the torque produced by three supramaximal stimuli.

  This evaluation will be carried out at rest, pre-intervention and immediately after the intervention

• Muscle Fatigue Index

  Characterized by the maximal voluntary isometric contraction decrease after the fatigue protocol, it will be evaluated by dynamometry.

  During 5 sec minutes before and after of electrical stimulation protocol

• Fatigue Index from Evoked Torque

  Characterized by the decrease of the evoked torque during the fatigue protocol, the fatigue index from the evoked torque will be evaluated by dynamometry, and obtained by the analysis of evoked torque curves

  During 20 minutes of electrical stimulation

• Reduction of the torque evoked until reaching 50% of the torque evoked by the first contraction

  It will be obtained from the analysis of the evoked contractions' torque-time curves. The torque evoked by each contraction will be normalized by the torque evoked by the first contraction (which will correspond to 100%). The number of contractions until the relative evoked torque to undergo a 50% reduction in relation to the evoked torque of the initial contraction will be used for analysis.

  During 20 minutes of electrical stimulation

• Total work generated during the fatigue protocol

  The torque-time integral of the evoked torque curves during the fatigue protocol will be evaluated and correspond to the mechanical work of each evoked contraction. The sum of the torque curve integral of all evoked contractions during the fatigue protocol will be calculated to determine the total work evoked by each current during the fatigue protocol.

  During 20 minutes of electrical stimulation

• Discomfort level generated by electrical stimulation during the fatigue protocol

  Discomfort will be measured with a Visual Analogue Scale (0-100mm), where 0 and 100 mm correspond to no discomfort and worst perceived discomfort, respectively

  During 20 minutes of electrical stimulation

Study Arms (6)

FN-NMES - 20 Hz

EXPERIMENTAL

This group will receive a NMES-induced fatigue protocol, which will be applied to the femoral nerve (FN) using a stimulation frequency of 20 Hz. For this, the participant will be positioned on the isokinetic dynamometer (Biodex Medical System, Shirley - NY, USA) with the knee in 90° of flexion (0°=total extension). The participant will be instructed to remain relaxed and to not perform active muscle contraction.

Device: Electric stimulation

FN-NMES - 100 Hz

EXPERIMENTAL

This group will receive a NMES-induced fatigue protocol, which will be applied to the femoral nerve (FN) using a stimulation frequency of 100 Hz. For this, the participant will be positioned on the isokinetic dynamometer (Biodex Medical System, Shirley - NY, USA) with the knee in 90° of flexion (0°=total extension). The participant will be instructed to remain relaxed and to not perform active muscle contractions.

Device: Electric stimulation

MP-NMES - 20 Hz

EXPERIMENTAL

This arm will receive a NMES-induced fatigue protocol, which will be applied to the motor point (MP) of the rectus femoris muscle using a stimulation frequency of 20 Hz. For this, the participant will be positioned on the isokinetic dynamometer (Biodex Medical System, Shirley - NY, USA) with the knee at 90° of flexion (0°=total extension). The participant will be instructed to remain relaxed and to not perform active muscle contractions.

Device: Electric stimulation

MP-NMES - 100 Hz

EXPERIMENTAL

This arm will receive a NMES-induced fatigue protocol, which will be applied to the motor point (MP) of the rectus femoris muscle using a stimulation frequency of 100 Hz. For this, the participant will be positioned on the isokinetic dynamometer (Biodex Medical System, Shirley - NY, USA) with the knee at 90° of flexion (0°=total extension). The participant will be instructed to remain relaxed and to not perform active muscle contractions.

Device: Electric stimulation

FNMP-NMES - 20 Hz

EXPERIMENTAL

This group will receive a NMES-induced fatigue protocol, which will be applied to the femoral nerve (FN) and to the motor point (MP) of the rectus femoris muscle using a stimulation frequency of 20 Hz. For this, the participant will be positioned on the isokinetic dynamometer (Biodex Medical System, Shirley - NY, USA) with the knee at 90° of flexion (0°=total extension). The participant will be instructed to remain relaxed and to not perform active muscle contractions.

Device: Electric stimulation

FNMP-NMES - 100 Hz

EXPERIMENTAL

This group will receive a NMES-induced fatigue protocol, which will be applied to the femoral nerve (FN) and to the motor point (MP) of the rectus femoris muscle using a stimulation frequency of 100 Hz. For this, the participant will be positioned on the isokinetic dynamometer (Biodex Medical System, Shirley - NY, USA) with the knee at 90° of flexion (0°=total extension). The participant will be instructed to remain relaxed and to not perform active muscle contractions.

Device: Electric stimulation

Interventions

Electric stimulation DEVICE

Neuromuscular electrical stimulation will be applied at two sites to induce fatigue with stimulation frequency specified at the Arm/Group Descriptions. The electrical stimulation parameters to generate the fatigue protocol will be: biphasic pulsed current, pulse duration of 2 ms, and on:off times of 5:10s. The fatigue protocol will be applied with a current intensity sufficient to generate an evoked torque at a level of 20% of the MVIC, which will be maintained throughout the protocol. NMES will be maintained until reaching an intervention time of 20 minutes, generating 80 evoked contractions.

FN-NMES - 100 Hz; FN-NMES - 20 Hz; FNMP-NMES - 100 Hz; FNMP-NMES - 20 Hz; MP-NMES - 100 Hz; MP-NMES - 20 Hz

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Healthy individuals:
• young people of both sexes
• age between 18 and 40 years
• body mass index between 20 and 25 kg/m2
• and normal knee range of motion
• with no complaints of pain or presence of pathology in the dominant lower limb. -

You may not qualify if:

• Individuals with:
• any contraindication to maximal exercise
• having been treated with NMES in the last 3 months in the lower limb
• not tolerate electrical stimulation

Sponsors & Collaborators

• Marco Aurélio Vaz, PhD: lead

Study Sites (1)

Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul

Porto Alegre, Rio Grande do Sul, 90690-200, Brazil

Location

MeSH Terms

Conditions

Fatigue

Interventions

Electric Stimulation

Condition Hierarchy (Ancestors)

Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Intervention Hierarchy (Ancestors)

Physical Stimulation; Investigative Techniques

Study Officials

• Marco A Vaz, PhD

  Federal University of Rio Grande do Sul

  PRINCIPAL INVESTIGATOR

• Marco A Vaz, PhD

  Federal University of Rio Grande do Sul

  STUDY CHAIR

• Marco A Vaz, PhD

  Federal University of Rio Grande do Sul

  STUDY DIRECTOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: October 6, 2022
• First Posted: November 4, 2022
• Study Start: January 25, 2023
• Primary Completion: September 30, 2024
• Study Completion: December 30, 2024
• Last Updated: June 10, 2024

Record last verified: 2024-06

Locations

BR (1)