HAMSTRING TIGHTNESS AND LUMBAR LORDOSIS ANGLE ACROSS FUNCTIONAL SITTING POSTURES (LLA-HT)

CORRELATION BETWEEN HAMSTRING TIGHTNESS AND LUMBAR LORDOSIS ANGLE ACROSS FUNCTIONAL SITTING POSTURES IN SEDENTARY ADULTS.

The goal of this observational study is to learn about the relationship between hamstring tightness and the lumbar lordosis angle in sedentary adults across different sitting postures. The main question it aims to answer is:

Is hamstring tightness related to the lumbar lordosis angle across three functional sitting postures (upright, slumped, and forward-leaning)? It also asks whether hamstring tightness differs between men and women, whether it differs between the dominant and non-dominant leg, and whether the lumbar lordosis angle differs between men and women across the three postures.

Participants will have their hamstring tightness measured with the Active Knee Extension test and their lumbar lordosis angle measured with a bubble inclinometer while sitting in each of the three postures.

Study Overview

• Status: Not yet recruiting
• Conditions: Sedentary Behavior; Hamstring Tightness; Lumbar Lordosis; Posture Sitting Position
• Intervention / Treatment: Other: Hamstring tightness and lumbar lordosis assessment

Detailed Description

Prolonged sitting is a defining feature of contemporary sedentary lifestyles and an established risk factor for musculoskeletal disorders of the lumbar spine. During sustained sitting, the hip is held in flexion and the hamstring muscle-tendon unit is maintained in a shortened position, which over time is associated with reduced hamstring extensibility (hamstring tightness). Because the hamstrings originate from the ischial tuberosity, a loss of hamstring extensibility exerts a posteriorly directed pull on the pelvis, promoting posterior pelvic tilt. Through regional spinopelvic coupling, this change in pelvic orientation alters the sacral slope and, consequently, the lumbar lordosis angle.

Although the relationship between hamstring tightness and lumbar lordosis has been described previously, most existing studies have evaluated it in the standing position. Sedentary individuals, however, spend the majority of their day seated, where the line of gravity, baseline muscle activity, and passive tissue demands placed on the spine differ substantially from those in standing. Evidence is therefore limited regarding how hamstring tightness relates to the lumbar lordosis angle across the functional sitting postures encountered in daily life, and regarding how this relationship may vary by sex and between the dominant and non-dominant lower limb.

This cross-sectional observational study will be conducted on 110 sedentary adults (55 male and 55 female), aged 18 to 45 years, recruited according to predefined eligibility criteria. The sample size was determined using G*Power based on a bivariate-normal correlation model. Eligible participants will be sedentary (more than six hours of sitting per day and a physical-activity level below 600 MET-minutes/week on the International Physical Activity Questionnaire), with a body mass index below 30 kg/m², bilateral hamstring tightness, and no current low back pain or other exclusionary conditions.

Following screening and informed consent, each participant's demographic and anthropometric data will be recorded, and lower-limb dominance will be determined using a three-task behavioral battery. Hamstring tightness will be assessed bilaterally using the Active Knee Extension (AKE) test, recorded with a digital goniometer, with the mean of three trials used for analysis. The lumbar lordosis angle (T12-S2) will be measured using a double bubble inclinometer in three randomized functional sitting postures-upright, slumped, and forward-leaning-with the mean of three trials per posture used for analysis.

The primary aim is to examine the correlation between hamstring tightness and the lumbar lordosis angle in each of the three sitting postures. The secondary aims are to compare hamstring tightness between male and female participants, to compare hamstring tightness between the dominant and non-dominant lower limb, and to compare the lumbar lordosis angle between male and female participants across the three postures. Data will be analyzed using Pearson correlation coefficients, independent- and paired-samples t-tests, and a mixed-design analysis of variance, with the significance level set at p < 0.05.

• Study Type: Observational
• Enrollment (Estimated): 110

Contacts and Locations

• Study Contact: Name: Ahmed youssef, physiotherapist; Phone Number: +201008650006; Email: ahmedshamebella@gmail.com

Study Locations

• Egypt
  • Shubra Misr
    • Cairo, Shubra Misr, Egypt, 12616
      • Nasser institute hospital
      • Contact: nasser institute; Phone Number: 22039356; Email: Info@nasserinstitute.com

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

Sedentary adults of both sexes, aged 18 to 45 years, recruited from the Nasser institute hospital, and the surrounding community. Eligible participants are healthy individuals with a sedentary lifestyle (more than six hours of sitting per day and a physical-activity level below 600 MET-minutes per week on the International Physical Activity Questionnaire), a body mass index below 30 kg/m², and bilateral hamstring tightness, with no current low back pain or other excluding musculoskeletal, neurological, or spinal conditions

Description

Inclusion Criteria:

• Healthy adults aged 18-45 years.
• Sedentary occupation requiring > 6 hours of sitting per day.
• Active Knee Extension (AKE) angle >15°.
• Bilateral hamstring tightness.
• Sedentary individual as determined by IPAQ (MET≤ 600 min/week).
• Asymptomatic for low back pain at the time of testing.

Exclusion Criteria:

• History of significant low back pain requiring medical treatment in the past 12 months.
• Previous spinal surgery or structural spinal deformities.
• Lower extremity injury or surgery within the past 6 months.
• Neurological disorders affecting sensation or movement.
• Pregnant female or get birth in the last year.
• Body mass index (BMI) ≥ 30 kg/m².
• postural deviations resulting from shortening of the iliopsoas and erector spinae or insufficiency of the core stabilizers and hip extensors

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Sedentary adults; Sedentary adults aged 18-45 years (55 male, 55 female) with bilateral hamstring tightness and no current low back pain, assessed for hamstring tightness (Active Knee Extension test) and lumbar lordosis angle (bubble inclinometer) across three functional sitting postures (upright, slumped, and forward-leaning).	Other: Hamstring tightness and lumbar lordosis assessment; Hamstring tightness measured bilaterally with the Active Knee Extension test (digital goniometer) and lumbar lordosis angle (T12-S2) measured with a bubble inclinometer across three functional sitting postures. No therapeutic intervention is administered; these are observational measurements only.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Correlation between hamstring tightness and lumbar lordosis angle across three functional sitting postures	Hamstring tightness is measured as the Active Knee Extension (AKE) deficit in degrees (mean of three trials per limb, using a digital goniometer). The lumbar lordosis angle is measured in degrees using a bubble inclinometer (T12-S2, mean of three trials per posture) in three functional sitting postures: upright, slumped, and forward-leaning. The association between hamstring tightness and the lumbar lordosis angle is assessed for each posture using the Pearson correlation coefficient.	At a single assessment session (cross-sectional; Day 1).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in hamstring tightness between males and females	Hamstring tightness (bilateral mean Active Knee Extension deficit, in degrees) compared between male and female participants.	At a single assessment session (cross-sectional; Day 1).
Difference in hamstring tightness between the dominant and non-dominant lower limb	Hamstring tightness (Active Knee Extension deficit, in degrees) compared between the dominant and non-dominant limb. Limb dominance is determined using a three-task behavioral battery.	At a single assessment session (cross-sectional; Day 1).
Difference in lumbar lordosis angle between males and females across the three sitting postures	Lumbar lordosis angle (degrees, bubble inclinometer, T12-S2) compared between male and female participants in each of the three functional sitting postures (upright, slumped, forward-leaning).	At a single assessment session (cross-sectional; Day 1).

Collaborators and Investigators

• Sponsor: Cairo University

Study record dates

Study Major Dates

• Study Start (Estimated): August 1, 2026
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: June 27, 2026
• First Submitted That Met QC Criteria: June 27, 2026
• First Posted (Actual): July 2, 2026

Study Record Updates

• Last Update Posted (Actual): July 2, 2026
• Last Update Submitted That Met QC Criteria: June 27, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Lumbar lordosis; Hamstring tightness; Posterior pelvic tilt; Active Knee Extension test; Spinopelvic alignment; Sedentary adults; Sitting posture; Functional sitting postures; AKE test; bubble inclinometer; Pelvic tilt; Lumbopelvic rhythm; Limb dominance
• Additional Relevant MeSH Terms: Bone Diseases; Musculoskeletal Diseases; Spinal Diseases; Spinal Curvatures; Behavior; Lordosis; Sedentary Behavior
• Other Study ID Numbers: P.T.REC/012/006548

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes