Viscous Elastic Properties of Superficial Back Muscles in Individuals With Hyperkyphosis

Viscoelastic Properties of Superficial Back Muscles: A Comparative Study of Individuals With Hyperkyphosis and Healthy Controls

Thoracic hyperkyphosis is a common spinal deformity that may alter the biomechanical and viscoelastic properties of trunk muscles. This comparative study aims to investigate differences in the mechanical properties of selected back and chest muscles between individuals with hyperkyphosis and healthy controls.

A total of 88 participants will be categorized based on thoracic kyphosis angle (≥50° hyperkyphosis; <50° control). The kyphosis angle will be measured using a flexible ruler method. Muscle tone, stiffness, elasticity, and relaxation properties of the trapezius, erector spinae, and pectoralis major muscles will be assessed using a handheld myotonometer. Spinal appearance perception will be evaluated using a kyphosis-specific questionnaire.

The study is designed to examine whether differences exist in muscle mechanical properties and whether kyphosis severity is associated with asymmetry in viscoelastic muscle characteristics.

Study Overview

• Status: Completed
• Conditions: Hyperkyphosis; Viscoelasticity

Detailed Description

Thoracic hyperkyphosis is a frequently observed spinal deformity characterized by an excessive posterior curvature of the thoracic spine. Increased kyphotic posture is associated with altered biomechanical loading, postural imbalance, reduced functional capacity, and changes in muscle performance. Although previous studies have largely focused on muscle tightness and postural alignment, limited evidence exists regarding the viscoelastic mechanical properties of trunk muscles in individuals with hyperkyphosis.

The mechanical behavior of skeletal muscle-including tone, stiffness, elasticity, and relaxation properties-reflects neuromuscular adaptation and tissue integrity. Changes in spinal curvature may lead to asymmetrical loading patterns between the anterior and posterior trunk muscles, potentially resulting in measurable differences in muscle viscoelastic characteristics. Understanding these adaptations may provide insight into rehabilitation strategies targeting both anterior and posterior muscle groups.

This comparative study is designed to evaluate and compare the viscoelastic properties of selected trunk muscles in individuals with thoracic hyperkyphosis and healthy controls. Participants are classified into two groups based on thoracic kyphosis angle measurements: individuals with a kyphosis angle of 50 degrees or greater are assigned to the hyperkyphosis group, while those with an angle below 50 degrees form the control group. The thoracic kyphosis angle is assessed using a flexible ruler method.

Muscle mechanical properties of the upper trapezius, erector spinae, and pectoralis major muscles are assessed bilaterally using a handheld myotonometer device. Parameters recorded include muscle tone (frequency), stiffness, elasticity, and relaxation time. In addition, participants' perception of spinal appearance is evaluated using a kyphosis-specific spinal appearance questionnaire.

The primary objective of the study is to determine whether individuals with hyperkyphosis demonstrate altered or asymmetric viscoelastic muscle properties compared to healthy individuals. A secondary objective is to explore the relationship between kyphosis severity and muscle mechanical characteristics.

The results of this study are expected to provide further information regarding muscular adaptations associated with thoracic hyperkyphosis and to support the development of comprehensive rehabilitation approaches targeting anterior chest and posterior trunk musculature.

• Study Type: Observational
• Enrollment (Actual): 88

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Gaziantep
    • Gaziantep, Gaziantep, Turkey (Türkiye), 27090
      • Sanko Unıversıty

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

individual with hyperkyphosis

Description

Inclusion Criteria:

• Individuals with a kyphosis angle of ≥50° and ≤50º were evaluated for eligibility. The inclusion criteria were: having a hyperkyphosis degree of ≥50°, a physiologic curve of the thoracic degree of ≤50º, and voluntarily participating in the study.

Exclusion Criteria:

• individuals with scoliosis, Scheuermann's kyphosis, and other congenital spinal problems.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
individuals with hyperkyphosis; thoracic kyphosis angles of ≥ 50◦ hyperkyphosis

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Flexible Ruler	Flexible Ruler The flexible ruler method is a reliable method used to measure cervical, thoracic, and lumbar spine curvature. The measurement is taken using a 40 cm long flexible ruler while standing with arms relaxed at the sides, head upright, and eyes looking straight ahead. The C2 and C7 vertebrae are palpated and marked using removable adhesive skin markers. The flexible ruler is then placed over the cervical lordosis between these two points, and markers indicating the location of the C2 and C7 spinous processes are placed on it. The flexible ruler is placed on millimeter paper, and the resulting curve is reflected. A vertical angle is drawn from the peak of the curve to the baseline, and the cervical lordosis deviation angle is determined using an angle-to-angle connection	3 months
MyotonPro- Tone	Viscoelastic Properties of Muscles The MyotonPro® device can determine the stiffness, tone, and elasticity properties of muscles. This previously calibrated device creates a mechanical stimulus that induces the damped natural oscillations of the tissues using a 3 mm diameter probe placed perpendicular to the muscle with a non-invasive handheld feature. The resulting oscillations are recorded by an accelerometer. MyotonPro® is a valid and reliable method for determining muscle tone.	3 months
Kyphosis-Specific Spine Appearance Questionnaire	Kyphosis-Specific Spine Appearance Questionnaire The Kyphosis-Specific Spine Appearance Questionnaire consisted of 10 items on a Likert scale (1 to 5) regarding patients' perceptions of appearance; higher scores indicated worsening deformity and increased concern about kyphosis-specific appearance. The first item is based on drawings showing varying degrees of severity of hyperkyphosis deformity in the sagittal plane. Questions two through ten are based on textual questions that rate concerns about other aspects of spinal deformity appearance. The total score of the questionnaire is calculated as the average of the ten responses	3 months
myoton pro- stiffness	Viscoelastic Properties of Muscles The MyotonPro® device can determine the stiffness, tone, and elasticity properties of muscles. This previously calibrated device creates a mechanical stimulus that induces the damped natural oscillations of the tissues using a 3 mm diameter probe placed perpendicular to the muscle with a non-invasive handheld feature. The resulting oscillations are recorded by an accelerometer. MyotonPro® is a valid and reliable method for determining muscle stiffness.	3 months
myoton pro - elasticity	Viscoelastic Properties of Muscles The MyotonPro® device can determine the stiffness, tone, and elasticity properties of muscles. This previously calibrated device creates a mechanical stimulus that induces the damped natural oscillations of the tissues using a 3 mm diameter probe placed perpendicular to the muscle with a non-invasive handheld feature. The resulting oscillations are recorded by an accelerometer. MyotonPro® is a valid and reliable method for determining muscle elasticity.	3 months

Collaborators and Investigators

• Sponsor: Sanko University

Study record dates

Study Major Dates

• Study Start (Actual): November 1, 2025
• Primary Completion (Actual): December 15, 2025
• Study Completion (Actual): January 15, 2026

Study Registration Dates

• First Submitted: February 18, 2026
• First Submitted That Met QC Criteria: February 24, 2026
• First Posted (Actual): February 27, 2026

Study Record Updates

• Last Update Posted (Actual): February 27, 2026
• Last Update Submitted That Met QC Criteria: February 24, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: viscoelasticity; hyperkyphosis
• Additional Relevant MeSH Terms: Bone Diseases; Musculoskeletal Diseases; Spinal Diseases; Spinal Curvatures; Kyphosis
• Other Study ID Numbers: hakanpolat13

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No