Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University School of Medicine, 1441 Clifton Road, N.E. Room 205, Atlanta, GA, 30322, USA.
College of Health Professions, Medical University of South Carolina, Charleston, SC, USA.
Exp Brain Res. 2022 Apr;240(4):1093-1103. doi: 10.1007/s00221-022-06316-8. Epub 2022 Feb 5.
Muscle spindle afferent feedback is modulated during different phases of locomotor tasks in a way that facilitates task goals. However, only a few studies have studied H-reflex modulation during landing. This study aimed to characterize soleus (SOL) H-reflex modulation during the flight and early landing period of drop landings. Since landing presumably involves a massive increase in spindle afferent firing due to rapid SOL muscle stretching, we hypothesized H-reflex size would decrease near landing reflecting neural modulation to prevent excessive motoneuron excitation. The soleus H-reflex was recorded during drop landings from a 30 cm height in nine healthy adults. Electromyography (SOL, tibialis anterior (TA), medial gastrocnemius, and vastus lateralis), ankle and knee joint motion and ground reaction force were recorded during landings. Tibial nerve stimulation was timed to elicit H-reflexes during the flight and early ground contact period (five 30 ms Bins from 90 ms before to 60 ms after landing). The H-reflexes recorded after landing (0-30 and 30-60 ms) were significantly smaller (21-36% less) than that recorded during the flight periods (90-0 ms before ground contact; P ≤ 0.004). The decrease in H-reflex size not occurring until after ground contact indicates a time-critical modulation of reflex gain during the last 30 ms of flight (i.e., time of tibial nerve stimulation). H-reflex size reduction after ground contact supports a probable neural strategy to prevent excessive reflex-mediated muscle activation and thereby facilitates appropriate musculotendon and joint stiffness.
肌梭传入反馈在运动任务的不同阶段被调节，以促进任务目标的实现。然而，只有少数研究研究了落地过程中 H 反射的调制。本研究旨在描述跖屈肌（SOL）在下落式跳跃落地的飞行和早期触地阶段的 H 反射调制。由于落地时 SOL 肌肉的快速拉伸可能会导致肌梭传入纤维放电大量增加，我们假设 H 反射幅度会在接近落地时减小，反映出神经调节以防止过度的运动神经元兴奋。在九名健康成年人从 30 厘米的高度下落式跳跃落地时记录 SOL 的 H 反射。在落地时记录肌电图（SOL、胫骨前肌（TA）、腓肠肌内侧和股外侧肌）、踝关节和膝关节运动以及地面反力。在飞行和早期触地期间（从触地前 90 毫秒到触地后 60 毫秒的五个 30 毫秒的 bin），通过刺激胫神经来诱发 H 反射。触地后（0-30 和 30-60 毫秒）记录的 H 反射明显较小（比飞行期间小 21-36%；P ≤ 0.004）。直到触地后 H 反射幅度才减小，表明在飞行的最后 30 毫秒内（即胫神经刺激的时间），反射增益的时间关键调制。触地后 H 反射幅度减小支持一种可能的神经策略，以防止过度的反射介导的肌肉激活，从而促进适当的肌腱和关节刚度。
