Effect of Electrical Stimulation and Exercise on Blood Flow in Patients With Resistant High Blood Pressure

• Study Rationale: Resistant hypertension (RH) remains a significant clinical challenge, often requiring four or more medications to achieve blood pressure control. Chronic sympathetic overactivity is a hallmark of RH. (TENS) has shown promise in modulating autonomic tone, while IE is known to improve endothelial function and vascular resistance. However, the combined effect of these two non-pharmacological interventions on peripheral hemodynamics in RH patients has not been fully explored.
• Objectives: The primary objective of this study is to investigate the effect of a combined program of TENS and IE on peripheral hemodynamic parameters, including (Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP), Pulse Pressure (PP) and Heart Rate Variability (HRV) in patients diagnosed with RH.
• Study Design and Procedures: 50 Participants from both sexes will be randomly assigned using closed envelop to either the Experimental Group (Combined Intervention) or the Control Group (Conventional physical therapy program)

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• Experimental group TENS protocol It will be used to stimulate the cervicothoracic sympathetic outflow (C7-T4), which contributes to the modulation of sympathetic activity, a key factor in the pathophysiology and management of resistant hypertension (RH) Electrode placements: bilaterally over the Paraspinal muscles at the T1-T5 levels (upper thoracic region), targeting sympathetic outflow to the cardiovascular system.

-Frequency: 2-10 Hz (low frequency stimulation)

-Pulse duration: 200 microseconds

-Intensity: strong but comfortable tingling sensations, below motor threshold (typically between 10-20mA)

-Session duration: 30 minutes per session

-Session frequency: 3 times per week

-Total intervention duration: 8 weeks IE protocol Handgrip Dynamometer: It will be used for isometric exercise training. The majority of IET research has utilized a handgrip (dynamometer) protocol, generally performed at 30% of the participant's maximal voluntary contraction (MVC)

-Hand grip dynamometer.

-30% of the participants' maximal voluntary contraction (MVC).

-Duration per trial: 2 minutes.

-Number of trials per session: 4 repetitions

-Rest interval between trials: 1 minute

-Session frequency: 3 sessions per week

-Total session duration: 14 minutes

• Control group Conventional physical therapy programs

• Aerobic exercise The control group will participate in a supervised overground brisk walking program, which serves as the contemporary standard of care for non-pharmacological blood pressure management. The program is designed to meet the latest physical activity clinical practice guidelines for hypertensive populations.

Setting and Monitoring sessions will be conducted in a climate-controlled, flat-surface indoor corridor. To ensure the accuracy of the prescribed intensity, participants will be equipped with a digital heart rate monitor (pulse oximeter) and a stopwatch. Baseline hemodynamic parameters, including resting blood pressure and heart rate, will be recorded before each session to ensure patient stability.

Brisk Walking Protocol The intervention will be performed three times per week for eight consecutive weeks. Each session is structured into three distinct phases (Lopes et al., 2021).

Warm-up Phase (5 minutes): Participants will engage in low-intensity walking at a self-selected pace, integrated with dynamic mobilization exercises for the lower limbs to enhance neuromuscular readiness.

Conditioning Phase (20-30 minutes): Participants will perform brisk walking at moderate intensity. This intensity is defined as 50% to 70% of the age-predicted maximum heart rate (220 - age). According to recent consensus, this level of exertion corresponds to a score of 11 to 13 on the Borg Rating of Perceived Exertion (RPE) scale.

Cool-down Phase (5 minutes): The session will conclude with gradual deceleration and static stretching of the major muscle groups (quadriceps, hamstrings, and gastrocnemius) to facilitate the gradual return of heart rate to baseline and prevent post-exercise syncope.

• Dynamic resistance exercise (weight training): Patients in the control group will undergo a standardized, supervised Dynamic Resistance Training (DRT) program. This protocol is designed based on the AHA/ACSM guidelines for hypertensive patients, focusing on large muscle groups with minimal equipment to ensure safety and clinical reproducibility.

• Exercise Parameters (FITT Principle) Frequency: 3 sessions per week on non-consecutive days. Intensity: Moderate intensity, defined as 40%-50% of 1-Repetition Maximum (1-RM) or a Rating of Perceived Exertion (RPE) of 11-13 on the Borg Scale (Fairly Light to Somewhat Hard).

Time: Approximately 30-40 minutes per session. 2. Exercise Selection

The circuit consists of simple, functional movements to improve peripheral vascular conductance:

Lower Body: Partial Squats (using a chair for support) and Calf Raises. Upper Body: Dumbbell Chest Press (supine) and Bicep Curls. Core: Pelvic Tilts (supine) to avoid intra-abdominal pressure spikes. 3. Structure of the Session Warm-up: 5 minutes of low-intensity walking or active range of motion exercises.

Conditioning Phase: 2-3 sets of 10-12 repetitions for each exercise. Rest Periods: A mandatory 90-second rest between sets to prevent cumulative blood pressure elevation.

Breathing Technique: Patients are strictly instructed to use rhythmic breathing (exhale during exertion) to avoid the Valsalva maneuver.

Cool-down: 5 minutes of static stretching and deep breathing exercises. -Stretching exercise A standardized static stretching program will be implemented. This protocol follows the ACSM guidelines to improve the range of motion and facilitate a reduction in systemic vascular resistance.

• Stretching Parameters Type: Static stretching (passive and active-assisted). Frequency: 3 days per week (integrated at the end of each exercise session). Intensity: Stretch to the point of "mild discomfort" or "feeling of tightness," but not pain.

Duration: Each stretch is held for 30 seconds. Volume: 2 repetitions for each muscle group. 2. Muscle Groups Targeted

The focus is on large muscle groups to maximize the effect on peripheral blood flow:

Lower Body:

Hamstrings: Seated toe touch or supine hamstring stretch. Gastrocnemius (Calf): Wall-supported calf stretch. Quadriceps: Standing or side-lying quad stretch.

Upper Body:

Pectoralis: Doorway chest stretch (to improve thoracic expansion). Upper Trapezius: Gentle neck lateral flexion. Triceps: Overhead triceps stretch. - Breathing Exercise This protocol is designed to be performed at the beginning or end of each session to promote systemic vasodilation.

• Technique: Diaphragmatic Breathing (Paced Breathing) Position: Patients are placed in a comfortable supine position with knees slightly bent or seated in a supportive chair.

Procedure:

The patient places one hand on the upper chest and the other on the abdomen (just below the rib cage).

Inhalation: Breathe slowly through the nose for 4 seconds, ensuring the abdomen rises while the chest remains relatively still.

Exhalation: Breathe out slowly through pursed lips for 6 seconds. Breathing Rate: Aim for 6 breaths per minute (this frequency is specifically shown to optimize baroreflex sensitivity).

• Parameters Frequency: 3 sessions per week (integrated into the physical therapy program). Duration: 10-15 minutes per session. Intensity: Effortless and relaxed; the patient should not feel short of breath or strained.
• Clinical Monitoring The physical therapist monitors the patient for any signs of dizziness or hyperventilation.

Emphasis is placed on the prolonged exhalation phase, which triggers the relaxation response and reduces peripheral vascular resistance.

-General Advice for Both Groups: Minimize sedentary behavior Maintain a healthy weight

Nutritional advice like:

Eat at least 5 portions of fruit and vegetables Eat more lean protein e.g. Fish and nuts Eat less salt <5g or 1tsp Eat 25-29 g of fiber Limit alcohol Drink 2-3 cups of coffee and/or tea (unsweetened)

Others:

Sleep: 7-9h/day Reduce stress: practice meditation or yoga 30 min per day Listen to music at least 25 min, 3 times per week Stop smoking Limit pollutions exposure Use digital wearables/apps to track movement

Inclusion criteria

• Age between 50 and 60 years. Both sexes were included Patients had been diagnosed with hypertension for at least 5 years.

Patients had resistant hypertension according to (Whelton et al 2018), defined as:

• Systolic blood pressure (SBP) ≥140 mmHg and/or diastolic blood pressure (DBP) ≥90 mmHg despite the use of three or more antihypertensive medications of different classes, including a diuretic,
• or controlled blood pressure (<140/90 mmHg) while on four or more antihypertensive medications.

Body Mass Index (BMI) 25: 34.9 kg/m²

Increased waist circumference, defined as:

• Greater than 102 cm for males.
• Greater than 88 cm for females.

Exclusion criteria

• Secondary hypertension due to identifiable causes (e.g., renal artery stenosis, primary aldosteronism, pheochromocytoma).
• History of major cardiovascular events in the last 6 months (e.g., myocardial infarction, stroke, or heart failure exacerbation).
• Severe musculoskeletal or neurological disorders that impair the ability to perform isometric exercise safely (e.g., recent joint replacement, severe osteoarthritis, stroke with residual motor deficit).
• Contraindications to the use of Transcutaneous Electrical Nerve Stimulation (TENS):

Implanted electronic devices: pacemakers, cardioverter defibrillators. Uncontrolled arrhythmias. Sever skin condition: open wounds, rashes, burns, eczema. Peripheral neuropathy or sensory loss.

-Known cognitive impairment or psychiatric conditions that would limit the ability to follow instructions or provide informed consent.