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Biomedical subjects

M Whitehurst

Publications and source records attributed to M Whitehurst.

8 recordsLinked to original sources
PubMed2001

Functional mobility performance in an elderly population with lumbar spinal stenosis.

OBJECTIVES: To compare the functional mobility (FM) of elderly apparently healthy (AH) subjects and patients with lumbar spinal stenosis (LSS) and to evaluate the reliability and validity of the FM tests. DESIGN: Using the test-retest paradigm, FM performance was assessed in AH subjects. A single FM assessment was conducted on a group of LSS subjects. Between-group performance comparisons were made with the AH subjects and the LSS patients. SETTING: Orthopedic clinical practice (LSS subjects) and university laboratory (AH subjects). PARTICIPANTS: Fifty-seven patients seen in an orthopedic clinical practice for LSS and 96 AH subjects who were volunteers identified from among participants of The Lifelong Learning Society at Florida Atlantic University. INTERVENTIONS: Treadmill walk (TW) test (at 53.6 m/min, 1% increase in grade per min) until 70% of the predicted maximum heart rate was achieved or associated pain made participation uncomfortable. Three trials each of a sit-to-stand (SS, rise from chair as quickly as possible without using arms) and a weight-carrying (WC, walk 20 m as quickly as possible for time carrying 10% of the body weight evenly distributed in hand-held weights) test. The AH group repeated all tests on a separate day. MAIN OUTCOME MEASURES: Time to walk treadmill, stand from sitting position, walk 20 meters, and analysis of variance between groups. RESULTS: Significant between-group differences were found for the TW, SS, and WC tests. Test-retest r values of .839 for the TW, .848 for the SS, and .833 for the WC were observed. CONCLUSIONS: The AH group demonstrated greater FM than the LSS group. The performance disparity between groups may suggest context validity, while the AH groups test-retest stability reflects reliability.

Activities of Daily Living↗
PubMed1995

The effect of velocity and gender on load range during knee extension and flexion exercise on an isokinetic device.

Limb acceleration and deceleration during exercise on an isokinetic device encounter no machine-offered resistance. The purpose of this study was to quantify the relationship between velocity and range of motion that is sustained at a predetermined isokinetic velocity, termed load range, during concentric knee extension and flexion exercise. Nine male and nine female subjects performed three maximal concentric reciprocal knee extension and flexion repetitions at 60, 120, 180, 240, 360, and 450 degrees/sec. Extension and flexion results revealed a significant (p < 0.05) increase in acceleration and deceleration range of motion while load range significantly decreased with increasing velocity. Males exhibited greater load range and less acceleration range of motion than females at 240, 360, and 450 degrees/sec, while deceleration range of motion was not different between genders at any speed. These results demonstrate an inverse relationship between isokinetic velocity and load range and suggest a need to carefully consider velocity selection when performing exercise on an isokinetic device.

Adult↗
PubMed1991

Reaction time unchanged in older women following aerobic training.

The effect of aerobic exercise on reaction time in older women was investigated. 14 women (M age = 65 yr.) were carefully screened for health status and lifestyle, then assigned to a random order of the exercise and control groups (ns = 7). Pre- and posttraining tests of aerobic capacity, simple reaction time, and choice reaction time were administered. The exercise group rode a stationary bicycle ergometer for 8 consecutive weeks for 3 35- to 40-min. sessions per week. There were no significant pretraining differences between groups on simple reaction time, choice reaction time, or estimated VO2max. No posttraining differences for simple and choice reaction time were found even though the exercise group had a significantly higher VO2max than the controls. Contrary to some other findings, the data indicate that reaction time may be independent of aerobic training in healthy older women.

Aged↗
PubMed1985

Initial characterization of sheep T-cell growth factor and its species-restricted activity on human, rat, and mouse cells.

Sheep T-cell growth factor (TCGF) was prepared from concanavalin A-activated sheep peripheral blood cells and subsequently characterized by ammonium sulfate precipitation, gel exclusion chromatography, and isoelectric focussing. The TCGF was found in the 60-80% ammonium sulfate fraction and was shown to have an apparent molecular weight of 32,500 and an isoelectric point in the range pI 5.2-5.5. The ability of the sheep TCGF to promote proliferation of activated human, sheep, mouse, and rat cells was compared with that of human TCGF prepared by phytohemagglutinin stimulation of lymphocytes from multiple donors and TCGF prepared from concanavalin A-stimulated rat and mouse spleen cells. Human TCGF was found to act across all species barriers, rat TCGF supported the growth of cells of all species except human, and mouse only promoted the growth of activated mouse and rat cells. Sheep TCGF was unique in being unable to support the growth of any cells except autologous cells.

Animals↗
PubMed1984

The production of T-cell growth factor (TCGF) in vivo in sheep.

Lymph and supernatants derived from efferent lymphocytes leaving the popliteal lymph nodes of sheep responding to human red cells or dinitrophenylated bovine serum albumin were examined for the presence of T-cell growth factor (TCGF). Efferent cells from normal sheep, but not from antigen-stimulated sheep, were found to release low levels of TCGF when incubated in medium for 12 hr in the absence of any exogenous stimulus. High levels of TCGF were found in normal lymph and also in immune lymph collected from sheep during the first 6 hr of immune responses. There were no detectable levels of TCGF in lymph collected later in the response. The lymphokine appeared to be a single molecular species of 10,000-20,000 molecular weight as assessed by exclusion chromatography. Efferent cells expressing receptors for TCGF were found in efferent lymph during the first 12 hr of the response. The results demonstrate for the first time that TCGF is produced in vivo and that asynchrony exists between TCGF production and expression of receptors for TCGF on efferent cells released by the stimulated node. Based on the known kinetics of previously reported synergistic factors, mitogenic factors, and T-cell-replacing factors in sheep efferent lymph and their physical characteristics it was concluded that the TCGF detected in lymph is distinct from these factors.

Animals↗
PubMed1983

Effects of contextual interference, task difficulty, and levels of processing on pursuit tracking.

Based on an activity questionnaire, 48 females without experience in open sports skills were selected to track a moving light beam through either a circle, square, or triangular target area on a pursuit rotor. Contextual interference was created by presenting 5 velocities in either a random or a blocked context during acquisition. Level of processing was manipulated by having half of all subjects classify acquisition velocities by a predetermined numerical code. Time-on-target (TOT) was measured after each acquisition, retention, and transfer trial. Subjects tracking the circle produced higher TOTs than those who tracked the square or triangle (which did not differ from one another) across all three phases of the experiment; blocked and random acquisition groups were not significantly different from one another in acquisition, retention, or transfer. Subjects who classified acquisition velocities and tracked the circle under the blocked acquisition context produced significantly higher retention scores than those who tracked the circle but did not classify acquisition velocities. Transfer was facilitated for subjects who tracked the triangle in a random transfer context and classified velocities during acquisition. Results were discussed as providing support for the manipulation of the level of cognitive processing during the initial stage of learning. In addition, manipulating task difficulty was discussed.

Adult↗