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Biomedical subjects

A H Sanford

Publications and source records attributed to A H Sanford.

7 recordsLinked to original sources
PubMed2001

Trunk muscle coactivation in preparation for sudden load.

Biomechanical stability of the lumbar spine is an important factor in the etiology and control of low-back disorders. A principle component of biomechanical stability is the musculoskeletal stiffening generated by preparatory muscle coactivation. The goal of this investigation was to quantify preparatory behavior, evaluating trunk muscle activity immediately prior to sudden trunk flexion loading during static extension tasks compared to activity observed when subjects were informed no sudden load would occur. Coactive excitation was also examined as a function of fatigue and gender. Results demonstrated increased extensor muscle and flexor muscle coactivation following static fatiguing exertions, potentially compensating for reduced trunk stiffness. Female subjects produced greater flexor antagonism than in the males. No difference in the preparatory coactive muscle recruitment patterns were observed when subjects were expecting a sudden flexion load compared to recruitment patterns observed in similar static postures when subjects were informed no sudden load would be applied. This indicates the neuromuscular system relies greatly on response characteristics for the maintenance of stability in dynamic loading conditions.

Adult↗
PubMed2000

Lumbar-pelvic coordination is influenced by lifting task parameters.

STUDY DESIGN: Low back kinematics, including relative lumbar and pelvic motions, were quantified during controlled lifting tasks. OBJECTIVES: To evaluate the influence of load and lifting velocity on lumbar-pelvic (LP) coordination. SUMMARY OF BACKGROUND DATA: Sagittal trunk extension is achieved through the coordinated motion of the pelvis and lumbar spine. There are no data to indicate whether lifting task design influences lumbar-pelvic coordination. METHODS: Lumbar and pelvic motions were recorded from 18 healthy subjects while performing isokinetic lifting tasks of 0.1 kg and 10 kg. Coordinated motions of the pelvis (sacral spine) and low-thoracic spine were evaluated using eigenvector analyses and a ratio of lumbar and pelvic angles (L/P). RESULTS: Eigenvector models of the lumbar-pelvic coordination accurately represented empirical coordination profiles. Weight significantly influenced lumbar-pelvic coordination. Trunk extension velocity demonstrated a small but statistically significant influence on lumbar-pelvic coordination. Weight and trunk flexion angle significantly influenced lumbar/pelvic angle ratios. CONCLUSIONS: Trunk extension was achieved through simultaneous but nonlinear contributions from both the pelvis and lumbar spine throughout the range of motion. The lumbar spine accounted for 70% of the total, with increased pelvic contributions in flexed postures. Task weight increased the lumbar contribution to total trunk motion. When performing clinical evaluations of spinal kinematics, it is necessary to recognize that unloaded motions may not fully represent loaded behavior of spinal coordination.

Adult↗
PubMed1990

Yersinia enterocolitica abscess of the transverse colon. Report of a case.

Yersinia enterocolitica abscess of the bowel is a rare entity. Only five cases have previously been reported--none in the surgical literature. A unique presentation for Yersinia infection, abscess of the transverse colon, is described, and the literature of Y. enterocolitica intestinal perforation and abscess is reviewed.

Abscess↗
PubMed1976

Ambiguity of the thymidine index.

The observed thymidine indices of seven experimental tumor lines are compared as a function of duration of emulsion exposure. The effects of dose level of tritiated thymidine and background threshold are also evaluated. The results indicate that an arbitrary high background threshold discriminates against "lightly" labeled cells at short periods of exposure but that the chosen threshold becomes less critical with longer exposure. The observed thymidine index increases with increasing duration of emulsion exposure but appears to approach a plateau for all tumor systems. The "thymidine index curves" are significantly different for each tumor. There is an inverse relationship between the dose of tritiated thymidine and the duration of exposure required to recognize the same fraction of cells as labeled in a given tumor. Similar experimental conditions do not necessarily guarantee a valid basis for comparison of observed thymidine indices among tumors.

Animals↗