This randomized controlled trial investigates the acute effects of three electrotherapy modalities (therapeutic ultrasound, interferential current, and TENS) on the mechanical and viscoelastic properties of neck muscles in young adults with forward head posture. Seventy-five participants will be randomly allocated to one of three groups. Muscle stiffness, oscillation frequency, and craniovertebral angle will be assessed before and immediately after a single treatment session.
Forward head posture (FHP) is a common postural deviation associated with increased mechanical loading of the cervical spine and altered muscle length-tension relationships. While electrotherapy modalities are widely used clinically to manage neck pain, their acute effects on the biomechanical and viscoelastic properties of cervical muscles remain insufficiently characterized. This study will evaluate the acute effects of therapeutic ultrasound, interferential current, and TENS on the dynamic stiffness, oscillation frequency, elasticity, and pain of the upper trapezius, splenius capitis, sternocleidomastoid, and cervical erector spinae muscles, measured using myotonometry (MyotonPRO) immediately before (T0) and after (T1) a single treatment session.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
75
Pulsed therapeutic ultrasound applied to the cervical region at 1-3 MHz frequency and 0.1-3 W/cm² intensity for 8-10 minutes in prone position, using circular head movements.
Bipolar interferential current applied via two electrodes covering the target muscles, \~2500 Hz carrier frequency, 100 Hz amplitude modulation frequency, for 15 minutes, at an intensity producing a clear but painless paresthesia sensation, in prone position.
Conventional TENS applied via surface electrodes covering the target muscles, 60-120 Hz frequency, 50-100 µsec pulse duration, for 15 minutes, at an intensity producing a clear but painless paresthesia sensation, in prone position.
Change in Dynamic Stiffness (N/m)
Dynamic stiffness reflects the resistance of the muscle to an external deforming force. It will be measured using MyotonPRO on the upper trapezius, splenius capitis, sternocleidomastoid, and cervical erector spinae muscles. The normative reference range for stiffness (S) is 220-380 N/m.
Time frame: Baseline (T0) and immediately after single intervention session (T1)
Change in Oscillation Frequency (Hz)
Oscillation frequency reflects the resting muscle tone. It will be measured using MyotonPRO on the same muscle groups. The normative reference range for oscillation frequency (F) is 12.0-18.0 Hz.
Time frame: Baseline (T0) and immediately after single intervention session (T1)
Change in Craniovertebral Angle (degrees)
The craniovertebral angle (CVA) is the angle between a horizontal line passing through the tragus of the ear and a line connecting the tragus to the spinous process of C7, and it is used to assess forward head posture. It will be measured from photographs using the Kinovea 2D motion analysis software. According to Salahzadeh et al. (2014), the mean CVA value in individuals without forward head posture is 55 degrees.
Time frame: Baseline (T0) and immediately after single intervention session (T1)
Change in Muscle Elasticity (Logarithmic Decrement)
The logarithmic decrement reflects muscle elasticity, describing how quickly the natural oscillation of the muscle decays after mechanical perturbation. It will be measured using MyotonPRO on the same muscle groups. The normative reference range for logarithmic decrement (D) is 1.00-1.60.
Time frame: Baseline (T0) and immediately after single intervention session (T1)
Change in Mechanical Stress Relaxation Time
Mechanical stress relaxation time reflects the viscoelastic properties of the muscle, specifically the time required for the muscle to relax after removal of an applied mechanical load. It will be measured using MyotonPRO on the same muscle groups. The normative reference range for relaxation time (R) is 14.0-30.0 ms.
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Time frame: Baseline (T0) and immediately after single intervention session (T1)
Change in Creep (Deformation/Relaxation Ratio)
Creep reflects the ratio between the deformation time and the relaxation time of the muscle and is used as an indicator of its viscoelastic behavior. It will be measured using MyotonPRO on the same muscle groups. The normative reference range for creep (C) is 1.00-2.00.
Time frame: Baseline (T0) and immediately after single intervention session (T1)
Change in Pain (Numeric Pain Rating Scale, 0-10)
Pain will be assessed using the Numeric Pain Rating Scale, an 11-point scale ranging from 0 to 10, where 0 indicates no pain and 10 indicates the worst pain imaginable. Participants who report pain will rate its severity using this scale.
Time frame: Baseline (T0) and immediately after single intervention session (T1)