Physiological Responses to Graded Manual Pressure in Healthy Adults: a Randomized Experimental Study on Autonomic, Hormonal, Sensory and Vascular Outcomes
Trial Snapshot
- Phase
- Not Applicable
- Status
- Not yet recruiting
- Sponsor
- Enrollment
- 90
- Locations
- 1
- Primary Endpoint
- Change in heart rate variability (HRV) index
Study Overview
Brief Summary
This randomized experimental study will investigate how different intensities and application patterns of manual pressure applied to the upper trapezius muscle affect physiological responses in healthy adults. Participants will be randomly assigned to one of three groups: (A) graded sustained pressure at a single point over the upper trapezius, (B) graded longitudinal kneading over a defined area of the upper trapezius, or (C) three standardized manual therapy protocols with increasing pressure (manual lymphatic drainage, light-pressure massage and moderate-pressure massage).
In groups A and B, five individualized pressure levels (0, 25, 50, 75 and 95% of each participant's pressure pain threshold) will be delivered for 2 minutes each in a single session. In group C, each participant will receive the three manual therapy protocols in separate randomized sessions. Autonomic (heart rate and heart rate variability), hormonal (capillary cortisol and VEGF in group C), sensory (mechanical pain thresholds), hemodynamic (blood pressure) and, in group C, vascular (left common carotid artery ultrasound) responses will be recorded before and after the interventions. The study will provide dose-response and mechanistic information to inform safer and more individualized manual therapy protocols.
Detailed Description
This prospective randomized experimental study will be conducted in healthy adults to characterize acute physiological responses to different intensities and patterns of manual pressure applied to the upper trapezius muscle. Participants will be randomly allocated to one of three experimental groups:
- Group A - Graded sustained pressure: a personalized pressure scale is defined based on the individual pressure pain threshold (PPT) measured with an algometer. Five pressure levels are set at 0% (contact without pressure), 25%, 50%, 75% and 95% of PPT, and applied as sustained pressure at a single point over the upper trapezius.
- Group B - Graded longitudinal kneading: the same personalized pressure scale (0, 25, 50, 75 and 95% of PPT) is applied as longitudinal kneading distributed over a predefined area of the upper trapezius.
- Group C - Manual therapy protocols: each participant receives three standardized manual therapy protocols in separate sessions, with randomized order: manual lymphatic drainage (approx. 40 minutes at ~40 mmHg), light-pressure massage (0.5-0.8 N/cm², 20-30 minutes) and moderate-pressure massage (2-3 N/cm², 20 minutes), all targeting the upper trapezius and related regions.
In groups A and B, the five pressure levels are each applied for 2 minutes in a single experimental session, in randomized order, with rest periods of at least 5 minutes between levels (extended if needed until heart rate returns within ±10% of baseline). In group C, each manual therapy protocol is applied in a separate session with at least one day between sessions. In all groups, heart rate and heart rate variability are recorded continuously with a chest strap, and skin temperature and skin conductance are continuously monitored with surface sensors. Blood pressure, mechanical pain thresholds (von Frey filaments at predefined trapezius and forearm sites), and capillary blood samples for cortisol are obtained at baseline and immediately after each pressure level or massage protocol. In group C, VEGF is also measured in capillary blood.
In group C only, duplex ultrasound of the left common carotid artery is performed under standardized conditions (semi-recumbent position, head rotated 45° to the right) before the manual therapy protocol and 10 minutes after its completion, to assess luminal diameter, intima-media thickness and peak systolic velocity. All pressure applications in all groups are monitored with a pressure-sensing system (Loadpad) placed on the therapist's hand.
A separate visit includes whole-body dual-energy X-ray absorptiometry (DEXA) to characterize body composition (total and segmental lean mass and fat mass). The main outcome is a heart rate variability index (e.g., RMSSD), while hormonal (cortisol, VEGF in group C), sensory (pain thresholds), hemodynamic (blood pressure) and vascular (carotid ultrasound in group C) measures are considered secondary outcomes. The study is powered assuming a large effect size on HRV based on previous massage research, with a planned sample size of 30 participants per group (N = 90).
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Parallel
- Primary Purpose
- Basic Science
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to 65 Years (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Age 18-65 years.
- •Healthy volunteers without diagnosed cardiovascular, neurological or severe musculoskeletal disorders.
- •No significant pain or pathology in the cervical, shoulder or upper back region that would interfere with pressure application.
- •Ability to understand the study procedures and to provide written informed consent.
- •Availability to attend the experimental session and the DEXA visit.
Exclusion Criteria
- •History of major cardiovascular disease (e.g., ischemic heart disease, heart failure, clinically significant arrhythmias, uncontrolled hypertension, stroke or transient ischemic attack).
- •Neurological disorders affecting pain perception or autonomic function.
- •Acute or chronic musculoskeletal conditions in the cervical or shoulder region that contraindicate manual pressure on the upper trapezius.
- •Coagulation disorders or high-dose anticoagulant/antiplatelet therapy that increases bleeding risk.
- •Dermatologic conditions or skin lesions at sensor placement or pressure application sites.
- •Pregnancy or suspected pregnancy (due to DEXA scan).
- •Regular use of medications with a major impact on autonomic or cardiovascular responses (e.g., beta-blockers, antiarrhythmics) that cannot be paused according to medical judgement.
- •Substance abuse or acute alcohol/drug intake in the 24 hours prior to the experimental session.
- •Any other condition that, in the opinion of the investigators, may compromise safety or compliance.
Arms & Interventions
Experimental: Sustained Pressure
Participants receive a graded manual pressure protocol applied as sustained pressure at a single point over the upper trapezius muscle (0, 25, 50, 75 and 90% of individual PPT, 2 minutes each level, randomized order).
Intervention: Graded Sustained Pressure (Other)
Experimental: Longitudinal Kneading
Participants receive the same graded pressure protocol applied as longitudinal kneading over a defined area of the upper trapezius muscle (0, 25, 50, 75 and 90% of individual PPT, 2 minutes each level, randomized order).
Intervention: "Manual Pressure Protocol" (Other)
Experimental: Manual Therapy Protocols
Participants receive three standardized manual therapy protocols with increasing pressure in three separate sessions, with randomized order: (1) manual lymphatic drainage (~40 mmHg, approximately 40 minutes), (2) light-pressure massage (0.5-0.8 N/cm², 20-30 minutes) and (3) moderate-pressure massage (2-3 N/cm², 20 minutes), targeting the upper trapezius and related regions.
Intervention: Manual Therapy Protocols (DLM, light and moderate-pressure massage) (Other)
Outcomes
Primary Outcomes
Change in heart rate variability (HRV) index
Time Frame: Baseline and after10 min
Heart rate variability (HRV) will be recorded continuously using a chest strap. An HRV index (e.g., RMSSD or SDNN) will be calculated for predefined periods (baseline, during and after each pressure condition). The primary outcome will be the change in HRV across pressure levels and between intervention groups.
Secondary Outcomes
- Change in capillary cortisol level(Baseline and after10 min)
- Change in mechanical pain threshold (von Frey)(Baseline and after10 min)
- Change in blood pressure(Baseline and after10 min)
- Change in skin temperature(Periprocedural)
- Change in skin conductance(Periprocedural)
- Change in common carotid artery diameter(Baseline and after10 min)
- Change in common carotid artery intima-media thickness (IMT)(Baseline and after10 min)
- Change in common carotid artery peak systolic velocity (PSV)(Baseline and after10 min)
- Body composition (DEXA)(Baseline)
- Change in capillary VEGF level(Baseline and after10 min)
Investigators
Vanesa Abuín
Principal Investigator
Universidad Europea de Madrid