Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, Institute of Neurology, University of Genova, Largo Daneo 3, 16132, Genoa, Italy.
Eur J Appl Physiol. 2014 Feb;114(2):359-64. doi: 10.1007/s00421-013-2778-5. Epub 2013 Dec 1.
Post-activation depression (PaD) refers to the inhibition of the H-reflex induced by a preceding conditioning stimulus able to activate the afferents mediating the H-reflex itself. PaD can be investigated assessing the frequency-related depression of the H-reflex. This parameter, which is highly correlated to the severity of spasticity, has been used in the longitudinal assessment of spastic patients, in particular to assess the effect of drugs and rehabilitation over the years. However, in such longitudinal assessment, changes observed might be age related and not only disease related. The aim of this study was to investigate the possible age effects on PaD.
The frequency-related depression of the flexor carpi radialis (FCR) H-reflex was examined in two groups of young (20 subjects; 28 ± 3 years) and aged (18 subjects; 69 ± 6 years) healthy subjects. PaD was evaluated by comparing the H-reflex amplitudes obtained with a stimulation frequency of 0.1 Hz with those obtained using higher frequencies (0.33-0.5-1-2 Hz).
The results showed that frequency-related depression of the FCR H-reflex is similar in young and elderly subjects at all frequencies, with the exception of 2 Hz.
Our study shows that ageing does not affect the frequency-related depression of the FCR H-reflex at the frequencies of 1 Hz or lower, supporting the reliability of this method to assess PaD in the clinical practice, particularly for the longitudinal assessment of spasticity. A decrease of GABA-ergic presynaptic inhibition seems to be the more likely explanation for the age-related changes that we observed at the frequency of 2 Hz.
后激活抑制（PaD）是指先前的条件刺激抑制了自身传入纤维介导的 H 反射，从而导致 H 反射的抑制。可以通过评估 H 反射的频率相关抑制来研究 PaD。该参数与痉挛严重程度高度相关，已用于痉挛患者的纵向评估，特别是用于评估多年来药物和康复的效果。然而，在这种纵向评估中，观察到的变化可能与年龄有关，而不仅仅与疾病有关。本研究旨在探讨 PaD 可能存在的年龄效应。
在两组年轻（20 名受试者；28±3 岁）和老年（18 名受试者；69±6 岁）健康受试者中，检查了屈肌腕桡侧（FCR）H 反射的频率相关抑制。通过比较 0.1 Hz 刺激频率下获得的 H 反射幅度与较高频率（0.33-0.5-1-2 Hz）下获得的 H 反射幅度，评估 PaD。
结果表明，FCR H 反射的频率相关抑制在年轻和老年受试者在所有频率下相似，除了 2 Hz 以外。
我们的研究表明，年龄不会影响 FCR H 反射在 1 Hz 或更低频率下的频率相关抑制，支持该方法在临床实践中评估 PaD 的可靠性，特别是用于痉挛的纵向评估。在我们观察到的 2 Hz 频率下，GABA 能突触前抑制的减少似乎是年龄相关变化的更可能解释。
