Effects of Functional Electrical Stimulation on Metaboreflex Activation in Healthy Individuals

Study Overview
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Brief Summary
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Cardiovascular exercise adjustments are required during in order to redistribute blood flow from non-exercising vascular areas to active muscles. This hemodynamic adjustments, which are partially mediated by mechanosensitive and metabosensitive reflexes, ultimately increase oxygen and nutrient delivery to exercising muscle tissues (Mitchell, 1990). Static handgrip exercise has been shown to induce alterations in the arterial baroreflex function (Kim, 2005) and activation of muscle metaboreflex that increases arterial blood pressure and peripheral vasoconstriction, respectively. Functional electrical stimulation (FES) treatment used in physical therapy in patients who are unable to tolerate conventional exercise showed to be a good alternative for muscle strengthening (Sbruzzi, 2010) and to improve metabolic abnormalities (Karavidas, 2006). However, the effect of FES on metaboreflex activation in healthy individuals has never been investigated. Therefore, this study aims to evaluate the metaboreflex activation induced by FES in upper and low limbs in healthy individuals, and also to compare their results with the effects caused by isometric exercise.

Detailed Description
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All participants will be invited to attend four separate days for completion of the study protocols. On the first day, the metaboreflex activation in upper limb will be randomly assigned to isometric exercise or FES intervention. On the second day, at least two days apart, random isometric exercise or FES intervention will be performed in the upper limb. On the third day, at least one week apart, all participants will be assigned to perform metaboreflex in a lower limb induced by isometric exercise or FES intervention. On the fourth day, at least two days apart, random isometric exercise or FES intervention will be performed in a lower limb. To evaluate the isometric exercise and FES intervention the post-exercise ischemia will be randomly performed to evaluate the accumulation of metabolites in response to activated limb (PECO +) and evaluation control without ischemia (PECO-). The experiments between PECO+ and PECO- will be separated by a 30 min interval. During isometric exercise and FES protocols the blood flow and peripheral vascular resistance will be assessed by venous occlusion plethysmography. Fatigue will be determined every minute by the 10-point Borg scale to assess rate of perceived exertion and by blood lactate. Blood lactate will be evaluated through capillary action at pre, immediately post exercise and at 5 minutes during the recovery period. Hemodynamic variables such as BP and HR will be recorded every minute during the protocols.

Official Title
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Effects of Functional Electrical Stimulation Compared to Isometric Exercise on Metaboreflex Activation in Healthy Individuals: Randomized Crossover Clinical Trial

Conditions
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Reduction of Blood Flow

Intervention / Treatment
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* Other: Functional electric stimulation
* Other: Isometric exercise


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy individuals Both genders Aged 35-70 years Sedentary Not using continuous medications Exclusion Criteria: Cardiovascular disease Neurological disease Malignant disease Peripheral vascular disorders (varicose veins or deep vein thrombosis) Peripheral sensitivity alterations Contraindication to performing physical exercise Refusal to sign the consent form

Ages Eligible for Study
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Minimum Age: 35 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Functional electric stimulation<br>Other: The FES will be placed at the flexor muscles of the forearm and knee extensors, for evaluation of upper and lower limbs, respectively. | Other: Functional electric stimulation<br>* The FES will be placed at the flexor muscles of the forearm and knee extensors, for evaluation of upper and lower limbs, respectively. The stimulation frequency will be 20 Hz. The pulse width used will be 0.5 milliseconds and the contraction time will be 60 seconds (TON: 60s) with a 1-second rest interval (TOFF: 1s). The total time of application will be determined for the muscle fatigue that will be evaluated by 10-point Borg scale and by the measurement of lactate accumulation that must not exceed 30 minutes. The intensity will be adjusted individually, taking into account the patient's ability to promote the full flexion of the wrist / knee extension and comfort during contractions. Along with the application of FES a 1 Kg overload will be applied to intensify the fatigue time.<br>* Other names: FES;|
| Placebo Comparator: Isometric exercise<br>For the upper limbs the isometric contraction exercise with handgrip will be performed for 5 minutes with 30% of loading, previously measured by maximum voluntary contraction test. | Other: Isometric exercise<br>* For the upper limbs the isometric contraction exercise with handgrip will be performed for 5 minutes with 30% of loading, previously measured by maximum voluntary contraction test. For the lower limbs the knee extension exercise will be conducted in a training station. The SBP, DBP, MBP and HR will be recorded through the protocols. Fatigue will be determined every minute by the 10-point Borg scale and by measurement of lactate accumulation before, immediately after the protocol, and 5 minutes during the recovery period.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Forearm and calf blood flow change | When performed the protocol with FES measurements will be taken for 3 minutes of rest (in both PECO+ and PECO-), 5 minutes of exercise (when PECO-) or to fatigue (when PECO +), during the 3 minutes of occlusion (when PECO +) and 3 minutes final recovery (in both PECO+ and PECO-). When performed the protocol with isometric exercise measurements will be at 3 minutes basal (in both PECO+ and PECO-), 3 minutes of exercise (in both PECO+ and PECO-), 3 minutes of occlusion when PECO + and 3 minutes of ultimate recovery (in both PECO+ and PECO-). | 5 minutes of exercise ( when PECO-) or to fatigue (when PECO +) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Maximum muscle strength | Before starting the evaluations of blood flow, the maximum peak strength is measured three times with 1 minute interval between each measurement, after is calculated 30% of the maximum value and the determined load exercise. | The maximum peak strength will be measured 3 times with 1 minute interval between each measurement before a session of isometric exercise | 
| Peripheral vascular resistance | Ratio between the mean arterial pressure (MBP) and muscle blood flow. | It is calculated using data obtained from blood flow and mean arterial pressure in the protocols at 3 minutes in both PECO+ and PECO- | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Metaboreflex, Variation of blood flow, Functional electrical stimulation, Isometric exercise.