"Physiological Responses to Manual Pressure in Healthy Adults"

Condition(s) studied

Investigational drug(s) / intervention(s)

"Manual Pressure Protocol": Manual pressure is applied over the upper trapezius muscle using five individualized pressure levels (0, 25, 50, 75 and 90% of the pressure pain threshold). Each level is applied for 2 minutes in a single experimental session, with randomized order and rest periods between applications. In the Sustained Pressure arm, pressure is maintained at a single point. In the Longitudinal Kneading arm, the same pressure levels are distributed along a predefined area using a kneading technique.

Manual Therapy Protocols (DLM, light and moderate-pressure massage): Three standardized manual therapy protocols targeting the upper trapezius and related regions are applied in separate sessions with at least one day between them and randomized order: (1) manual lymphatic drainage (approx. 40 minutes at \~40 mmHg), (2) light-pressure massage (0.5-0.8 N/cm², 20-30 minutes) and (3) moderate-pressure massage (2-3 N/cm², 20 minutes). Pressure is monitored continuously with a hand-worn pressure sensor.

Graded Sustained Pressure: Manual pressure applied over the upper trapezius using five individualized pressure levels (0, 25, 50, 75 and 95% of the pressure pain threshold) delivered as sustained pressure at a single point, 2 minutes per level in a single session, with randomized order and rest periods between applications.

Study 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.

Eligibility

Primary outcome measure(s)

• Change in heart rate variability (HRV) index — 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.

Trial sites (1)

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