Differential control of H-reflex amplitude in different weight-bearing conditions in young and elderly subjects

作者：Tsuruike Masaaki^*; Kitano Koichi; Koceja David M; Riley Zachary A

来源：Clinical Neurophysiology, 2012, 123(10): 2018-2024.

DOI：10.1016/j.clinph.2012.03.006

• Elderly
• H-reflex
• Presynaptic inhibition
• Weight bearing

Objective: This study measured the modulation of conditioned (femoral nerve, paired-stimuli) and unconditioned soleus H-reflexes in young and elderly subjects when changing weight-bearing (WB) requirements and body position.
Methods: Conditioned and unconditioned H-reflexes were examined in 14 elderly subjects and 11 young subjects during six different WB conditions: (1) lying supine with no WB, (2) supine position inclined by 30 degrees with 50% WB, (3) standing with 50%, (4) 75%, (5) 100% and (6) 125% WB.
Results: The elderly subjects had consistently higher background soleus EMG activity across the WB conditions compared to the young. Femoral nerve conditioning caused facilitation of the H-reflex that changed across WB conditions in the young subjects, but not in the elderly subjects. Finally, elderly subjects had less depression with paired-stimulation (PRD) across WB conditions, which was not observed in the young subjects.
Conclusions: The elderly may have more direct activation of motoneurons from descending pathways, coupled with less segmental spinal control of inhibitory interneurons, as evidenced by the increased background soleus activity, H/M-max ratios and the lack of modulatory control observed when conditioning the H-reflex.
Significance: There was an age-specific response from descending and segmental pathways during conditions that involved either different WB requirements or changes in body position.

• 出版日期2012-10