Hoffman reflex (H-reflex) obtained in subjects of both sexes, ranging from 20 to 80 years old

THESES

HOFFMAN REFLEX (H-REFLEX) OBTAINED IN SUBJECTS OF BOTH SEXES, RANGING FROM 20 TO 80 YEARS OLD (ABSTRACT)^*. DISSERTATION. RECIFE, 1997.

MARCO AURÉLIO SMITH FILGUEIRAS ^**

The main objective of this study was to evaluate possible alterations of the Hoffmann reflex depending on the age, in 91 subjects, of both sexes, ranging from 20 to 80 years old.

H-reflexes were obtained from soleus and gastrocnemius muscles, applying a weak electrical stimulation in the Ia intrafusal fibers in the tibial nerve, at the popliteal region of both inferior limbs. Stronger stimulation is necessary for the recruitment of all muscle motor units (fast and slow fibers), giving rise to a maximal direct motor response. In order to compare reflex response in various ages we measured parameters such as stimulus intensity, latency (response time) reflex amplitude and the ratio between maximal H reflex and maximal M response (Hmax / Mmax).

There were significant statistical differences with respect to stimulus intensity, stronger stimulus being necessary for older subjects. Stronger stimulus intensity was also necessary for women than for men. This may be due to a greater resistance to pulse current in women, as a result of a thicker fat layer. Latency was greater in men than in women because men are taller, however latency was always longer in older subjects. Amplitude of reflex responses decreased with age, starting at age 40. This decrease was greater and statistically significant from ages 60 to 80. The ratio Hmax / Mmax decreased with age mainly due to reflex amplitude decrease.

The results of this work lead to the following information:

a) there is no age influence in H reflex parameters for subjects in the range of 20 to 40 years of age. In this great young adults age range, reflex differences were observed among sexes, due to morphological and functional features, stronger stimulus intensity being necessary for women. Lactency for men were longer because men have longer legs (longer reflex arc);

b) stimulus intensity has to be stronger for older subjects;

c) latency of reflex response increases significantly in advanced ages;

d) the amplitude of the reflex responses decreases as age increases;

e) the maximal H reflex to maximal M response (Hmax / Mmax) decreases with increasing age.

KEY WORDS: H-reflex, age, older subjects, sex, Hmax / Mmax.

*

Reflexo de Hoffmann (reflexo H) obtido de pessoas de ambos os sexos, com idade variando de 20 a 80 anos (Resumo). Dissertação de Mestrado, Universidade Federal de Pernambuco (Área: Neuropsiquiatria). Orientador: Manuel Moreira da Costa.

**

Address: Avenida Monteiro da Franca 1063, 58038-320 João Pessoa PB, Brasil.

Publication Dates

• Publication in this collection
  06 Nov 2000
• Date of issue
  Dec 1998