Biomedical Technology Laboratory, Movement Biomechanics and Motor Control Lab, Department of Electronic, Information and Bioengineering, Politecnico di Milano, Milan, Italy.
Gait Posture. 2013 Sep;38(4):951-5. doi: 10.1016/j.gaitpost.2013.04.025. Epub 2013 May 24.
A biomechanical study of the head-neck complex in seated subjects was conducted to verify whether a slight load, applied at the back of the head, could beneficially affect the head-neck posture, one of the factors of postural neck pain. An eccentric load of 0.5 kg was applied to the subjects' head by means of a special cap. A group of asymptomatic subjects (n=10, 28.9±12.1 yrs), and a group of subjects that had experienced mild, occasional neck pain (n=10, 39.6±18.4 yrs) were compared. They were analyzed while maintaining a still posture that was periodically perturbed to avoid habituation. A 3D motion analyzer and reflective markers placed over the head, the neck and the trunk, were used to compute head inclination and translation and head/neck flexion angle in different conditions: before, during and after having had the load applied for 15 min. Although the moment induced by the load was extensor, a forward-oriented movement of the head was observed in both groups. However, the forward displacement, in relation to the initial position, was smaller in the mild neck pain group than in the asymptomatic group (5.7±4.7 mm vs. 8.9±5.5 mm, P<0.05 and 2.6±5.9 mm vs. 11.0±9.0 mm after 15 min, P<0.05). After removing the load, the mild neck pain subjects assumed a retracted position (-3.8±2.7 mm) while the asymptomatic subjects stayed protracted (+3.5±5.1 mm, P<0.01). These unexpected findings suggest that a slight load added to the head can influence the postural control mechanisms and, in symptomatic subjects, lead to a new strategy aimed at a reduction of the neck extensor muscle contraction.
一项针对坐姿受试者头颈部复合体的生物力学研究旨在验证头部施加轻微负荷是否可以有益地影响头颈部姿势，这是姿势性颈痛的因素之一。通过特殊帽子向受试者头部施加 0.5 公斤的偏心负荷。将一组无症状受试者（n=10，28.9±12.1 岁）和一组经历过轻度、偶发性颈痛的受试者（n=10，39.6±18.4 岁）进行比较。他们在保持静止姿势的同时进行分析，这种姿势会周期性地受到干扰，以避免习惯化。使用三维运动分析器和放置在头部、颈部和躯干上的反射标记来计算头倾斜和平移以及头/颈弯曲角度在不同条件下的变化：在施加负荷之前、期间和之后 15 分钟。尽管负荷引起的力矩是伸展的，但在两组受试者中都观察到头向前的运动。然而，与初始位置相比，轻度颈痛组的向前位移较小（5.7±4.7 毫米对 8.9±5.5 毫米，P<0.05 和 2.6±5.9 毫米对 11.0±9.0 毫米 15 分钟后，P<0.05）。去除负荷后，轻度颈痛受试者采取回缩位置（-3.8±2.7 毫米），而无症状受试者保持伸展位置（+3.5±5.1 毫米，P<0.01）。这些意外的发现表明，头部施加的轻微负荷可以影响姿势控制机制，并且在有症状的受试者中，导致一种新的策略，旨在减少颈部伸肌收缩。
