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Biomedical subjects

S J Sullivan

Publications and source records attributed to S J Sullivan.

76 records · Page 5Linked to original sources
PubMedDate not supplied

The reliability of H-reflex recordings in standing subjects.

OBJECTIVE: Several studies have used the H-reflex to investigate the effect of upright stances and locomotion on spinal reflex excitability. The reliability of eliciting this reflex during weight-bearing has however yet to be addressed. This study was undertaken to determine the reliability of individual differences in the H-reflex recorded from healthy subjects during quiet standing. Secondary aims of the study were to evaluate individual reliability during prolonged standing, and to establish the minimum number of trials required to provide reliable measurements of the H-reflex. DESIGN AND PARTICIPANTS: Twenty neurologically healthy volunteers participated in a repeated measures design consisting of 8 blocks of 20 trials evenly distributed over two testing sessions. H-reflex recordings were elicited from the subject's dominant side soleus muscle by percutaneously stimulating the posterior tibial nerve. Stimuli were presented every 10 s, with 2 min seated rest provided between blocks of trials. Peak-to-peak amplitude of H-reflexes and m-responses determined for individual trials were used for subsequent analysis. RESULTS: It was found that the reliability of measuring the H-reflex and m-response during quiet standing was extremely robust (r = .97 for both measures). This pattern of individual differences remained consistent over 80 trials confirming the stability of the measures. High reliabilities (r = .96 and .87 for the H-reflex and m-responses respectively) were also observed when as few as four trials were analysed. When measures obtained during the first session of testing were compared with those obtained for session two, the correlation coefficients were generally of a lower order (r = .54 to .90). DISCUSSION: The results demonstrate that the H-reflex in quiet standing provides high intra-individual reliability, suggestive of a stable reflex resistant to potentially confounding postural influences, or other sources of biological variation. The between-session reliability underscores the difficulty in reproducing conditions between sessions, and emphasises the need for within-session comparisons of H-reflex amplitudes. Given the functional challenge of maintaining an upright posture, the H-reflex appears to be a well maintained and stable phenomenon.

Adolescent↗
PubMedDate not supplied

Reliability of individual differences for H-reflex recordings.

Complementary data from two closely-related experiments were analyzed to investigate the reliability of individual differences of H-reflex amplitude. Some concomitant analysis of M-reflex was also included. The purpose was to do this in a manner that was more direct and more detailed than found hitherto in the literature. Fundamental techniques espoused particularly by F.M. Henry (1969) formed the basis of this approach. The aims included a clearer quantification of reliability with a distinction between inter- and intra-individual sources of variation, an analysis of the effects different numbers of trials had on reliability, and an investigation of the progression of reliability over a 20-trial sequence of observations. The control conditions of both experiments were designed to be essentially identical with respect to subject position, stimulus and recording configurations. Experiment 1 had 20 subjects, four control conditions of 10-trials in each while experiment 2 had 18 subjects, five control conditions and 20 trials. The posterior tibial nerve was percutaneously stimulated every 10 sec. and surface electromyographic recordings were made from the soleus muscle. H-reflex and M-reflex amplitudes were measured on every trial. It was found that the reliability of individual differences of both H-reflex and M-reflex was extremely robust with the majority of coefficients being above .950. In addition, the reliabilities remained high when as few as four trials were examined. The pattern of individual differences over the longer series of trials confirmed the stability of interindividual differences and showed that subjects became more consistent in their responses as trials progressed.(ABSTRACT TRUNCATED AT 250 WORDS)

H-Reflex↗
PubMedDate not supplied

Comparison of human triceps surae H-reflexes obtained from mid and distal recording sites.

The purpose of this study was to determine whether a distal triceps surae recording site produced H-reflex responses similar to those obtained from the conventional soleus location in 10 healthy subjects at rest. H-reflex and M-response recruitment profiles were generated and the peak-to-peak amplitudes were measured from the two sites simultaneously. Following this, an H-reflex control signal was determined (peak-to-peak amplitude approximately equal to 30% Mmax) and 4 series of 10 trials were recorded at 5 minute intervals. A paired t-test showed non-significant (p greater than 0.05) differences in Hmax, Mmax, and Hmax: Mmax values recorded from the two sites. Linear regression analyses of recruitment profile H-reflexes and M-responses, obtained simultaneously from the two recording sites showed strong correlations (r greater than 0.90, p less than 0.001). To assess the stability of the reflex over time, intraclass correlation coefficients (ICC) were computed for each recording site (R = 0.99 in both instances). Thus the distal recording site, just proximal to the flare of the medial malleolus, is an acceptable alternative to the conventional recording location. This permits recording H-reflex amplitude changes, resulting from the application of a therapeutic intervention to the calf muscles, without having to remove and reposition the recording electrodes.

Adult↗