Effects of hamstring flexibility and trunk flexion posture on creep deformation of viscoelastic lumbar tissues:​ an exploratory study

Kang, Sang Hyeon

Affiliations

¹Human Performance Institute, Department of Industrial and Entrepreneurial Engineering and Engineering Management, Western Michigan University, Kalamazoo, MI, USA

Abstract and keywords

This study explores the effects of hamstring flexibility on the creep deformation of viscoelastic lumbar tissues and its interaction with trunk flexion angles and exposure-recovery schedules. Sixteen participants, divided into two groups (low-flexible, high-flexible) based on hamstring flexibility, performed four 30-minute protocols with alternating intervals of trunk flexion (exposure) and upright standing (recovery). The protocols included combinations of two trunk flexion postures (maximal, submaximal) and two exposure-recovery schedules (3:6 min schedule, 1:2 min schedule) tested on four separate days. Before and after the protocol, trunk flexion–extension motions were employed to capture the changes in lumbar flexion angles of flexion-relaxation (EMG-off) in lumbar paraspinals, denoting lumbar spinal creep. The results revealed no significant main effect of individual hamstring flexibility but showed a significant interaction between flexibility and trunk flexion posture on the EMG-off lumbar flexion angles. The low-flexible group exhibited significantly greater EMG-off angles in the maximal posture (Δ2.4 on average) compared to the submaximal posture (Δ0.7), while the high-flexible group showed no effect. The analysis of lumbopelvic posture during sustained trunk flexion postures supported that altered pelvic angles as a function of individual hamstring flexibility may affect passive tissue loading at, or near, maximal flexion postures. These results suggest that reduced hamstring flexibility can play a significant role in spinal tissue creep with different trunk flexion postures. This work is a secondary analysis of a dataset previously published by Kang and Mirka (2025a), designed to address a distinct research question related to hamstring flexibility.

Keywords: Creep; Viscoelastic; Lumbar spine; Pelvis; Hamstring flexibility

Links

DOI: 10.1016/j.jbiomech.2025.112895

PubMed: 40782539

WoS: 001556029600001

History

Accepted: 2025-08-5

Online: 2025-08-6

Cited Works (8)

Year	Entry
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