School of Physical Education and Sport Science at Serres, Aristotle University of Thessaloniki, Thessaloniki, Greece; Laboratory of Evaluation of Human Biological Performance, School of Physical Education and Sport Science, Aristotle University of Thessaloniki, Thessaloniki, Greece.
School of Physical Education and Sport Science, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Exp Gerontol. 2022 Aug;165:111844. doi: 10.1016/j.exger.2022.111844. Epub 2022 May 26.
Examining how timely is sensory input processed and regulated after a perturbation while standing, is a key element to understand postural control, especially in people with balance deficits, such as older adults. In this study, we investigated the age-related temporal modulations in spinal excitability, by measuring the soleus H-reflex within the first 250 ms after switching on (V-ON) and off (V-OFF) a pair of vibrators, placed over the Achilles tendons.
Twenty young (25.1 ± 5.1 yrs) and 16 older (71.8 ± 6.1 yrs) adults stood blindfolded, while 12-15 s periods of Achilles tendon vibration (ATV) were applied with 20-24 s intervals. Anterior/posterior center of pressure and electromyographic (EMG) responses [soleus (SOL) and tibialis anterior (TA)] were assessed whereas SOL H-reflex normalized to maximum M-wave (H/M) and SOL EMG (H/SOL) were evaluated before ATV (Pre) and at 50, 100, 150, 200 and 250 ms after the V-ON and V-OFF.
Only in young adults the TA/SOL EMG ratio decreased 100 (p = 0.032) and 150 ms (p < 0.001) after V-ON and the H/M and H/SOL decreased 150-250 ms after V-ON (p < 0.001). At 50-250 ms after V-OFF, H/M was reduced compared to Pre values (p < 0.001), with no differences between the age groups (p > 0.05). H/SOL was decreased for the young adults (p < 0.001) and remained reduced at least for the first 250 ms after V-OFF. At 150 ms after V-OFF, SOL/M was decreased only for the older adults (p < 0.001), whereas TA/SOL EMG gradually increased for both groups (p < 0.001).
When ATV is introduced while standing, the spinal excitability of older people is reduced later and to a lesser extent compared to young adults. Their limited capacity to down-regulate the "noisy" sensory input generated by ATV gives further evidence of a possible mechanism for their inefficient postural control.
研究站立时感觉输入的处理和调节的及时性，是理解姿势控制的关键因素，尤其是在平衡能力受损的人群中，如老年人。在这项研究中，我们通过测量跟腱上一对振动器开启（V-ON）和关闭（V-OFF）后前 250 毫秒内的比目鱼肌 H 反射，研究了与年龄相关的脊髓兴奋性的时变调制。
20 名年轻（25.1±5.1 岁）和 16 名老年（71.8±6.1 岁）成年人在闭眼状态下站立，同时施加 12-15 秒的跟腱振动（ATV），间隔 20-24 秒。评估了前后中心压力和肌电图（EMG）反应[比目鱼肌（SOL）和胫骨前肌（TA）]，同时评估了 V-ON 前后 50、100、150、200 和 250 毫秒时的比目鱼肌 H 反射归一化至最大 M 波（H/M）和比目鱼肌 EMG（H/SOL）。
只有在年轻成年人中，V-ON 后 100 毫秒（p=0.032）和 150 毫秒（p<0.001）时 TA/SOL EMG 比值降低，V-ON 后 150-250 毫秒时 H/M 和 H/SOL 降低（p<0.001）。V-OFF 后 50-250 毫秒时，H/M 与预值相比降低（p<0.001），但两组之间无差异（p>0.05）。H/SOL 降低仅在年轻成年人中（p<0.001），并且在 V-OFF 后至少前 250 毫秒保持降低。V-OFF 后 150 毫秒时，仅老年组的 SOL/M 降低（p<0.001），而 TA/SOL EMG 逐渐增加（p<0.001）。
当站立时引入 ATV 时，与年轻成年人相比，老年人的脊髓兴奋性降低的时间更晚，程度更小。他们对 ATV 产生的“嘈杂”感觉输入的下调能力有限，这进一步证明了他们姿势控制效率低下的可能机制。
