Chen Yi-Lang, Liao Ying-Hua
Department of Industrial Engineering and Management, Ming Chi University of Technology, New Taipei 243303, Taiwan.
Taiwan Research Institute, New Taipei 251401, Taiwan.
Bioengineering (Basel). 2024 Jul 20;11(7):736. doi: 10.3390/bioengineering11070736.
Previous studies examining the flexion-relaxation phenomenon (FRP) in back muscles through trunk forward flexion tests have yielded inconsistent findings, primarily due to variations in leg posture control. This study aimed to explore the influence of leg posture control and individual flexibility on FRP in back and low limb muscles. Thirty-two male participants, evenly distributed into high- and low-flexibility groups, were recruited. Activities of the erector spinae, biceps femoris, and gastrocnemius muscles, alongside the lumbosacral angle (LSA), were recorded as participants executed trunk flexion from 0° to 90° in 15° increments, enabling an analysis of FRP and its correlation with the investigated variables. The findings highlighted significant effects of all examined factors on the measured responses. At a trunk flexion angle of 60°, the influence of leg posture and flexibility on erector spinae activities was particularly pronounced. Participants with limited flexibility exhibited the most prominent FRP under constrained leg posture, while those with greater flexibility and unconstrained leg posture displayed the least FRP, indicated by their relatively larger LSAs. Under constrained leg posture conditions, participants experienced an approximate 1/3 to 1/2 increase in gastrocnemius activity throughout trunk flexion from 30° to 90°, while biceps femoris activity remained relatively constant. Using an inappropriate leg posture during back muscle FRP assessments can overestimate FRP. These findings offer guidance for designing future FRP research protocols.
以往通过躯干前屈试验研究背部肌肉屈伸放松现象（FRP）的研究结果并不一致，主要原因是腿部姿势控制存在差异。本研究旨在探讨腿部姿势控制和个体柔韧性对背部及下肢肌肉FRP的影响。招募了32名男性参与者，平均分为高柔韧性组和低柔韧性组。当参与者以15°的增量将躯干从0°屈曲到90°时，记录竖脊肌、股二头肌和腓肠肌的活动以及腰骶角（LSA），以便分析FRP及其与研究变量的相关性。研究结果突出了所有检查因素对测量反应的显著影响。在躯干屈曲角度为60°时，腿部姿势和柔韧性对竖脊肌活动的影响尤为明显。柔韧性有限的参与者在腿部姿势受限的情况下表现出最明显的FRP，而柔韧性较好且腿部姿势不受限的参与者表现出的FRP最少，这体现在他们相对较大的腰骶角上。在腿部姿势受限的条件下，参与者在从30°到90°的整个躯干屈曲过程中，腓肠肌活动增加了约1/3至1/2，而股二头肌活动保持相对稳定。在背部肌肉FRP评估中使用不适当的腿部姿势会高估FRP。这些发现为未来FRP研究方案的设计提供了指导。
