The effects of percussive massage therapy on thoracolumbar fascia structure in low back pain patient

Fascia plays a potential role in developing chronic diseases[1], even cancer[2]. As the largest fascial structure in the body, the thoracolumbar fascia (TLF) is a composite structural material consisting of tendons and fascial planes that connects the latissimus dorsi and gluteus maximus muscles[3]. Its primary function is to help stabilize the spine and transmit forces between the lumbar spine and pelvis[4]. At the beginning of the twenty-first century, Langevin M proposed an interactive model of the pathogenesis of thoracolumbar fascia and lower back pain[5]. A subsequent series of studies found that the thoracolumbar fascia in patients with low back pain showed thickening[6], reduced shear strain[7], and structural disturbances [8] compared to individuals without low back pain. These changes in the TLF may induce pain by stimulating A- and C-fiber nociceptors[9, 10]. Fascial thickening has been found to vary, even in healthy individuals[11]. This is associated with fascial densification caused by overuse[12]. The abnormality of the fascial structure could be reversed by applying mechanical forces (twisting, tension, compression, stretching, bending and friction, percussion) to the soft tissues [5, 13, 14]. This phenomenon may be attributed to mechanical stimulation that increases the local strain on the loose connective tissue, causing hyaluronic acid hydration to reduce the viscosity[15]. Treatment of deep fascia requires adequate, and sustained pressure[16], thereby therapists often use power tools, such as handheld percussion devices, to improve fascial function[17, 18].
Recently, handheld percussive massage therapy (PT) has received increasing attention. Different manufacturers (e.g., Theragun, Hyperice) offer this equipment for self-massage or therapist treatment, which can usually provide up to 53Hz percussion frequency, 16mm amplitude, and various massage heads that can be matched to different body parts. Due to its portability and stability, PT is favored by the physical therapist community and sports people[17]. Available evidence suggests that PT can increase range of motion(ROM), improve recovery, and reduce muscle pain and stiffness [19–22]. The mechanism may be related to continuous percussion stretching the muscle fiber, causing collagen remodeling and elastin changes[13, 23], affecting the fascia's densification, adhesions, and viscoelastic properties [12]. A review showed that most therapists use PT to treat myofascial syndrome [17]. Although percussion massage has been widely used in therapeutic practice, there are no relevant studies on whether PT can affect the fascial structure.
This study aims to investigate the effects of PT on TLF morphology and other related outcomes. We hypothesized that 15 min of PT would reduce participants' TLF thickness, echo intensity of the ROI (range of interest) on TLF, and perceived stiffness, as well as increase skin temperature and lumbar flexibility.

筋膜在慢性疾病[1]，甚至癌症[2]的发生发展中扮演着潜在的角色。作为人体最大的筋膜结构，胸腰筋膜（TLF）由肌腱和筋膜平面组成，是连接背阔肌和臀大肌的复合结构性材料[3]。其主要功能在于协助稳定脊柱，并传递腰椎与骨盆之间的力量[4]。21世纪初，Langevin M 提出了胸腰筋膜和下背痛的发病机制互动模型[5]。随后的一系列研究发现，与无下背痛的个体相比，下背痛患者的胸腰筋膜表现出增厚[6]、剪切应变减少[7]和结构紊乱[8]。这些TFL的变化可能通过刺激A-和C纤维伤害感受器[9, 10]引起疼痛。研究发现，筋膜的增厚甚至在健康个体中也存在差异[11]。这与过度使用导致的筋膜致密化有关[12]。通过施加机械力量（扭转、张力、压缩、拉伸、弯曲和摩擦、敲击）于软组织，可以逆转筋膜结构的异常[5, 13, 14]。这种现象可能归因于机械刺激增加了松散结缔组织的局部应变，导致透明质酸水合作用降低粘度[15]。治疗深层筋膜需要充足且持续的压迫[16]，因此治疗师常常使用手持敲击装置等功率工具来改善筋膜功能[17, 18]。

近期，手持敲击按摩疗法（PT）受到了越来越多的关注。不同的制造商（例如，Theragun，Hyperice）提供此类设备用于自我按摩或治疗师治疗，通常可以提供高达53Hz的敲击频率、16mm的振幅，以及可匹配不同身体部位的多种按摩头。由于其便携性和稳定性，PT受到了物理治疗师和运动员的青睐[17]。现有证据表明，PT可以增加活动范围（ROM）、改善恢复，并减少肌肉疼痛和僵硬[19-22]。其机制可能与持续的敲击拉伸肌纤维，导致胶原蛋白重塑和弹性蛋白变化[13, 23]，影响筋膜的致密化、粘连和粘弹性特性[12]有关。一项综述显示，大多数治疗师使用PT治疗肌筋膜综合征[17]。尽管敲击按摩在治疗实践中已被广泛应用，但尚无相关研究探讨PT是否能够影响筋膜结构。

本研究旨在调查PT对TLF形态和其他相关结果的影响。我们假设15分钟的PT可以减少参与者的TLF厚度、TLF ROI（感兴趣区域）的回波强度、感知僵硬，并增加皮肤温度和腰椎灵活性。