The Third School of Clinical Medicine (School of Rehabilitation Medicine), Zhejiang Chinese Medical University, Hangzhou, China.
School of Rehabilitation Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China.
PeerJ. 2023 Jul 19;11:e15719. doi: 10.7717/peerj.15719. eCollection 2023.
The effect of foot, especially intrinsic muscles, on postural control and its related mechanisms remain unclear due to the complex structure. Therefore, this study aims to investigate the activation of intrinsic foot muscles in the elderly under static and dynamic postural tasks.
Twenty-one elderly participants were included to perform different postural tests (sensory organization test (SOT), motor control test (MCT), limit of stability test (LOS), and unilateral stance test) by a NeuroCom Balance Manager System. The participants were instructed to maintain postural stability under conditions with combined different sensory inputs (vision, vestibular, and proprioception) in SOT as well as conditions with translation disturbance in MCT, and to perform an active weight-shifting tasks in LOS. During these tasks, muscle activation were simultaneously acquired from intrinsic foot muscles (abductor halluces (AbH) and flexor digitorum brevis (FDB)) and ankle muscles (anterior tibialis, medial head of gastrocnemius, lateral head of gastrocnemius, and peroneus longus). The root-mean-square amplitude of these muscles in postural tasks was calculated and normalized with the EMG activity in unilateral stance task.
The activation of intrinsic foot muscles significantly differed among different SOT tasks ( < 0.001). tests showed that compared with that under normal condition 1 without sensory interference, EMGs increased significantly under sensory disturbance (conditions 2-6). By contrast, compared with that under the single-sensory disturbed conditions (conditions 2-4; 2 for disturbed vision, 3 for disturbed vestibular sensation, 4 for disturbed proprioception), activation was significantly greater under the dual-sensory disturbed postural tasks (conditions 5 and 6; 5 for disturbed vision and proprioception, 6 for disturbed vestibular sensation and proprioception). In MCT, EMGs of foot muscles increased significantly under different translation speeds ( < 0.001). In LOS, moderate and significant correlations were found between muscle activations and postural stability parameters (AbH, = 0. 355-0.636, < 0.05; FDB, = 0.336-0.622, < 0.05).
Intrinsic foot muscles play a complementary role to regulate postural stability when disturbances occur. In addition, the recruitment magnitude of intrinsic foot muscles is positively correlated with the limit of stability, indicating their contribution to increasing the limits of stability in the elderly.
由于足部结构复杂，其对姿势控制的影响及其相关机制仍不明确，尤其是内在肌肉。因此，本研究旨在探讨老年人在静态和动态姿势任务下内在足部肌肉的激活情况。
共纳入 21 名老年人，采用神经康平衡管理器系统进行不同的姿势测试（感觉组织测试（SOT）、运动控制测试（MCT）、稳定性极限测试（LOS）和单侧站立测试）。在 SOT 中，当存在视觉、前庭和本体感觉等多种感觉输入组合以及 MCT 中存在平移干扰的情况下，要求参与者维持姿势稳定性，并在 LOS 中进行主动负重转移任务。在这些任务中，同时从内在足部肌肉（拇展肌和趾短屈肌）和踝关节肌肉（胫骨前肌、腓肠肌内侧头、腓肠肌外侧头和腓骨长肌）获取肌肉激活情况。计算这些肌肉在姿势任务中的均方根振幅，并将其与单侧站立任务中的肌电图活动进行归一化。
不同 SOT 任务中内在足部肌肉的激活情况存在显著差异（<0.001）。测试表明，与正常状态 1 （无感觉干扰）相比，在感觉干扰下（条件 2-6），肌电图明显增加。相比之下，与单一感觉干扰条件（条件 2-4；2 为视觉干扰，3 为前庭感觉干扰，4 为本体感觉干扰）相比，在双重感觉干扰的姿势任务下（条件 5 和 6；5 为视觉和本体感觉干扰，6 为前庭和本体感觉干扰），激活更为明显。在 MCT 中，足部肌肉的肌电图在不同的平移速度下显著增加（<0.001）。在 LOS 中，肌肉激活与姿势稳定性参数之间存在中度和显著的相关性（拇展肌，=0.355-0.636，<0.05；趾短屈肌，=0.336-0.622，<0.05）。
当发生干扰时，内在足部肌肉发挥互补作用以调节姿势稳定性。此外，内在足部肌肉的募集程度与稳定性极限呈正相关，表明其有助于增加老年人的稳定性极限。
