RELATIONSHIP OF REDUCED HAMSTRING FLEXIBILITY WITH LUMBOPELVIC RHYTHM AND MUSCLE ACTIVATION

NCT07123012 | Completed

• 1 other identifier: SYU 2025-03-033-002
• Study Type: observational
• Target: 38
• Locations: 1 country
• Sites: 1

Brief Summary

Key Findings (narrative form) The study examined how hamstring flexibility influences the way the lumbar spine and pelvis share movement during forward bending and how this affects muscle activity.

• ≤ 60 ° (short hamstrings)
• 61-79 ° (moderate flexibility)
• ≥ 80 ° (good flexibility) Those in the ≤ 60 ° group showed a significantly higher lumbar contribution in both bending tasks than their more flexible peers. Once SLR exceeded roughly 60 °, additional gains in flexibility produced only modest further improvement in spine-pelvis balance, suggesting that 60 ° is a clinically important threshold.
• When the differences appear The greatest gap between flexibility groups occurred during the first half of the bend-particularly as participants began to lean forward. As they returned to upright, the differences narrowed. This indicates that early-phase movement is the critical moment when tight hamstrings shift load onto the lumbar spine.
• Impact on muscle activity Better hamstring flexibility was linked to a more even distribution of work between the lumbar extensor muscles and the hamstrings themselves. Participants with looser hamstrings did not have to activate their spinal muscles as forcefully, whereas gluteus maximus activity remained low in all groups because the tasks were unloaded.
• Hamstrings shorter than about 60 ° on the SLR "lock" the pelvis and make the lower back bend excessively, increasing spinal strain.
• Improving hamstring length shifts motion back toward the pelvis, reducing demand on lumbar joints and muscles.
• Even small everyday bends-such as reaching for an object on a chair-follow the same pattern, so stretching benefits daily life, not just sports performance.
• Patients and families can adopt simple hamstring-stretch routines; clinicians should consider targeted flexibility training whenever SLR is 60 ° or below before progressing to heavy lifting or core-stability programs. Limitations The study involved healthy young adults and measured only unloaded forward bending. Outcomes may differ in older individuals, manual laborers, or tasks that involve twisting or weight. Long-term research is needed to confirm that stretching actually prevents low-back pain. Bottom Line Flexible hamstrings let the pelvis and lower back "share the job." If your hamstrings are tight, your spine must work harder, which may invite discomfort or injury over time. A regular stretching program that brings SLR above roughly 60 ° can restore a healthier, more balanced bending pattern and help protect the lower back.

Conditions

Hip Functional Restriction; Lumbar Spine Biomechanics; Lumbar Muscle Activation

Keywords

hamstring muscles; Lumbar vertabrae; Pelvis; Electromyography; Range of Motion

Outcome Measures

Primary Outcomes (2)

• Lumbar Relative Contribution Index (RCI) During Full-Range Forward Bend

  Sagittal-plane RCI is defined as the percentage of total trunk excursion attributable to lumbar-spine motion while participants bend forward from upright to maximal comfortable flexion and return. Higher values indicate greater lumbar dominance. Mean RCI will be compared across three hamstring-flexibility groups (SLR ≤ 60°, 61-79°, ≥ 80°).

  Single assessment session (one day)

• Lumbar Relative Contribution Index (RCI) During Partial Forward Bend

  The sagittal-plane RCI is defined as the percentage of total trunk-flexion excursion attributable to lumbar-spine motion while the participant bends forward only until the fingertips touch the patella and then returns to upright. IMU data (T12, S2) are filtered at 6 Hz and processed to compute lumbar and pelvic angles; RCI is sampled at 10 % increments of the flexion and extension phases. Mean RCI values will be compared across three hamstring-flexibility groups (SLR ≤ 60°, 61-79°, ≥ 80°).

  Single laboratory visit; data captured during a ~15-minute test session for each participant.

Secondary Outcomes (1)

• Mean Normalised RMS EMG Amplitude of Lumbar Erector Spinae During First Half of Full-Range Forward Bend

  Single laboratory visit; data captured during a ~15-minute test session for each participant.

Study Arms (3)

Short

Individuals with an SLR of 60 ° or less

Normal

Individuals with an SLR between 60 ° and 80 °

Normal long

Individuals with an SLR of more than 80 °

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

The study population consists of healthy young adults aged 18 - 40 years. Participants will be recruited from the local community and university settings. Individuals included are those without any known musculoskeletal or neurological impairments, specifically with no history of lumbar or lower limb disorders, and who voluntarily agree to participate after providing informed consent.

You may qualify if:

• Healthy adults without musculoskeletal or neurological impairments
• Individuals without lumbar spine and lower limb disorders
• Participants who provided voluntary written informed consent

You may not qualify if:

• History of lumbar surgery or significant trauma
• Presence of acute or chronic pain conditions in lumbar or hip regions
• Neurological or orthopedic disorders affecting lumbar and hip functions
• Pregnancy
• Individuals unable to perform the required physical activities safely

Sponsors & Collaborators

• Sahmyook University: lead

Study Sites (1)

Sahmyook University

Seoul, Nowon-gu, 01795, South Korea

Location

Study Design

• Study Type: observational
• Observational Model: OTHER
• Time Perspective: CROSS SECTIONAL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: August 7, 2025
• First Posted: August 14, 2025
• Study Start: April 14, 2025
• Primary Completion: June 27, 2025
• Study Completion: June 27, 2025
• Last Updated: August 22, 2025

Record last verified: 2025-08

Locations

KR (1)