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Abstract：
Gait stability is the ability to deal with small perturbations that naturally occur during walking. Changes in motor control caused by pain could affect this ability. This study investigated whether nociceptive stimulation (hypertonic saline injection) in a low back (LBP) or calf (CalfP) muscle affects gait stability. Sixteen participants walked on a treadmill at 0.94ms(-1) and 1.67ms(-1), while thorax kinematics were recorded using 3D-motion capture. From 110 strides, stability (local divergence exponent, LDE), stride-to-stride variability and root mean squares (RMS) of thorax linear velocities were calculated along the three movement axes. At 0.94ms(-1), independent of movement axes, gait stability was lower (higher LDE) and stride-to-stride variability was higher, during LBP and CalfP than no pain. This was more pronounced during CalfP, likely explained by the biomechanical function of calf muscles in gait, as supported by greater mediolateral RMS and stance time asymmetry than in LBP and no pain. At 1.67ms(-1), independent of movement axes, gait stability was greater and stride-to-stride variability was smaller with LBP than no pain and CalfP, whereas CalfP was not different from no pain. Opposite effects of LBP on gait stability between speeds suggests a more protective strategy at the faster speed. Although mediolateral RMS was greater and participants had more asymmetric stance times with CalfP than LBP and no pain, limited effect of CalfP at the faster speed could relate to greater kinematic constraints and smaller effects of calf muscle activity on propulsion at this speed. In conclusion, pain effects on gait stability depend on pain location and walking speed.
摘要：
步态稳定性是处理行走过程中自然发生的小扰动的能力。疼痛引起的运动控制的变化可能会影响这种能力。这项研究调查了下背部（LBP）或小腿（CalfP）肌肉的伤害性刺激（高渗盐水注射）是否会影响步态稳定性。16名参与者在跑步机上以0.94ms（-1）和1.67ms（-1）的速度行走，而胸部运动学是使用3D运动捕捉记录的。从110步，稳定性(局部发散指数，LDE),沿三个运动轴计算胸廓线速度的跨步变异性和均方根（RMS）。在0.94ms(-1)时，独立于运动轴，步态稳定性较低（LDE较高），跨步变异性较高，在LBP和CalfP期间没有疼痛。这在CalfP期间更为明显，可能由步态中小腿肌肉的生物力学功能来解释，与LBP相比，中外侧RMS和站立时间不对称性更大，并且没有疼痛。在1.67ms(-1)时，独立于运动轴，与没有疼痛和CalfP相比，LBP的步态稳定性更大，步幅变异性更小，而CalfP与无疼痛没有什么不同。LBP对速度之间的步态稳定性的相反影响表明在更快的速度下具有更多的保护性策略。尽管中外侧RMS更大，并且参与者在CalfP下的不对称站立时间比LBP更多，并且没有疼痛，在较快的速度下，CalfP的有限影响可能与更大的运动学约束和小腿肌肉活动对该速度下推进的影响更小有关。总之,疼痛对步态稳定性的影响取决于疼痛位置和步行速度。
