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Biomedical subjects

A W Jackson

Publications and source records attributed to A W Jackson.

At least 19 recordsLinked to original sources
PubMed2004

Organization of higher-order brain areas that initiate locomotor activity in larval lamprey.

In the lamprey, spinal locomotor activity can be initiated by pharmacological microstimulation in several brain areas: rostrolateral rhombencephalon (RLR); dorsolateral mesencephalon (DLM); ventromedial diencephalon (VMD); and reticular nuclei. During DLM- or VMD-initiated locomotor activity in in vitro brain/spinal cord preparations, application of a solution that focally depressed neuronal activity in reticular nuclei often attenuated or abolished the locomotor rhythm. Electrical microstimulation in the DLM or VMD elicited synaptic responses in reticulospinal (RS) neurons, and close temporal stimulation in both areas evoked responses that summated and could elicit action potentials when neither input alone was sufficient. During RLR-initiated locomotor activity, focal application of a solution that depressed neuronal activity in the DLM or VMD abolished or attenuated the rhythm. These new results suggest that neurons in the RLR project rostrally to locomotor areas in the DLM and VMD. These latter areas then appear to project caudally to RS neurons, which probably integrate the synaptic inputs from both areas and activate the spinal locomotor networks. These pathways are likely to be important components of the brain neural networks for the initiation of locomotion and have parallels to locomotor command systems in higher vertebrates.

Animals↗
PubMed2000

Perceived submaximal force production in young adult males and females.

UNLABELLED: Clinical treatment in physical rehabilitation routinely uses perceived relative forces. PURPOSE: This study used psychophysical methods to quantify subjects' errors during submaximal muscular force production. METHODS: A sample of young adult (aged 23 +/- 3 yr) females (N = 60, 62 +/- 14 kg) and males (N = 50, 72 +/- 13 kg) performed a chest press on a hydraulic dynamometer with which they were unfamiliar. In four consecutive presses with a 2-min rest interval between each press, the subjects were asked to produce a force in the order of 25%, 50%, 75% of their maximal force, and a final maximal press. Pilot data (N = 10) indicated good reliability (r(xx) > 0.80) for the protocol. RESULTS: The rs between perceived force production and the desired production were 0.76 (P < 0.001) for males and 0.75 (P < 0.001) for females. The exponent for the power function between the perceived and desired forces was 1.12 for males and 1.03 for females. The total error ranged from 2.82 kg x m (males) to 1.22 kg x m (females). The rs and the logarithmic matching of perceived and desired force indicated a linear relationship that is consistent with Borg's range model, which has proposed that perceptual intensities of force for different people are approximately set equal at a subjective maximum. CONCLUSION: Many young healthy subjects can produce relative muscular forces with good accuracy. However, some subjects will provide very inaccurate forces that might affect outcomes in rehabilitation or physical training.

Adult↗
PubMed2000

Variables related to meeting the CDC/ACSM physical activity guidelines.

PURPOSE: The purpose of this study was to investigate the relation between perceived importance of physical activity and demographic variables and current physical activity level with specific reference to the CDC/ACSM guidelines for sufficient physical activity for a health benefit. METHODS: Physical activity levels were assessed by a telephone survey of 2002 households throughout the continental United States and the District of Columbia to determine whether the individuals met the CDC/ACSM physical activity guidelines. RESULTS: Results indicate that 68% of the respondents are physically active below the CDC/ACSM criterion. Chi-square analysis revealed significant relationships between meeting the CDC/ACSM physical activity guidelines and 1) perceived importance of physical inactivity as a health risk (P < 0.0001), and 2) gender (P < 0.0001). Logistic regression analysis revealed that having a greater awareness of the health risks of physical inactivity improved the odds ratio (OR = 1.40, 95% CI = 1.21-1.62) of being sufficiently physically active for a health benefit by 40% (P < 0.0001) and being a male improved the odds ratio (OR = 1.45, 95% CI = 1.17-1.79) of being sufficiently physically active for a health benefit by 45% (P < 0.0006). CONCLUSIONS: Implications for health and physical fitness researchers and practitioners are that they need to improve awareness of life span fitness benefits and develop intervention programs based on individuals' current physical activity levels.

Aged↗
PubMed2000

Reliability and validity issues concerning large-scale surveillance of physical activity.

The BRFSS is our major source of population-based information on physical activity in the United States. The top priority for the immediate future should be to make sure that the information obtained from the BRFSS in its current form is both reliable and valid. As outlined in this report, this task could be completed in relatively short time frame and at reasonable cost in terms of both financial and human resources. The development of an additional module to assess light-to-moderate activity and strength is currently underway with support from the CDC. As suggested in this report, this task may prove to be extremely difficult, or it may be difficult to develop an instrument of this type given the constraints of a population based telephone survey. The current focus on the health benefits of moderate activity and the interest in tracking this type of activity behavior on a population basis as it relates to national physical activity objectives both argue in favor of developing a physical activity assessment instrument that provides a valid and reliable measurement of moderate activity. Given the complexity and uncertainty of this task it is important to develop a procedure that will allow for periodic evaluation of progress and the potential for success to minimize the risk of making a considerable financial investment in an instrument that may be of limited utility.

Activities of Daily Living↗
PubMed1999

A one-year follow-up to physical activity and health. A report of the Surgeon General.

OBJECTIVES: A telephone survey of over 2000 American adults was conducted to determine their awareness of Physical Activity and Health: A Report of the Surgeon General and their knowledge of the health messages contained within the report. A related purpose was to determine if awareness and knowledge were a function of age, ethnicity, gender, and education level. METHODS: A random sample of American adults was drawn and a national telephone survey was conducted in the 48 contiguous states and the District of Columbia. RESULTS: Approximately one third of the adult population had heard of the report. Awareness was a function of age, ethnicity, and educational level. Knowledge of the relationship between physical inactivity and specific chronic diseases was a function of age, ethnicity, and gender. CONCLUSIONS: Differential awareness of the Report and its contents by various segments of the population has significant implications for the messages transmitted and interventions developed to help individuals adopt and maintain active lifestyles.

Adolescent↗
PubMed1998

Effect of oral creatine ingestion on parameters of the work rate-time relationship and time to exhaustion in high-intensity cycling.

The relationship between work rate (W) and time to exhaustion (t) during intense exercise is commonly described by either a hyperbolic function (NLin), t= W'/(W-Wcp), or by its linear equivalent (LinW) Wlim=W' + Wcp(t). The parameter Wcp (critical power) has been described as an inherent characteristic of the aerobic energy system, while W' has been shown to be a ralid estimate of anaerobic work capacity. Recent studies have demonstrated that oral supplementation of creatine monohydrate (CrH2O) increases total muscle creatine stores, and have linked these increases to improved performances in intense intermittent exercise. This study was conducted to determine the effect of CrH2O supplementation on estimates of W' and Wcp derived from the NLin and LinW equations, and to determine the effect of CrH2O on t in exhaustive constant power exercise of different intensities. Fifteen active but untrained university students completed three phases of testing on a cycle ergometer: (1) familiarization, three learning trials, (2) baseline determination of W' and Wcp, four bouts performed at a W selected to elicit fatigue in 90-600 s, and (3) experimental determination of W' and Wcp, four bouts performed at the same W as baseline, but performed after 5 days of ingesting either a placebo (4 x 6 g of glucose/day) or CrH2O (4 x 5 g of CrH2O and 1 g glucose/day). Testing was administered in a double-blind manner. Analyses of covariance revealed a significant effect for CrH2O on both estimates of W' (NLin, P=0.04; LinW, P < 0.01), but not on estimates of Wcp (NLin, P=0.37; LinW; P=0.30). Within groups, t was significantly different for only CrH2O at the two highest Ws (P=0.04). It is concluded that oral ingestion of CrH2O increases estimates of W' due to an improved t at the shorter, more intense exercise bouts.

Administration, Oral↗
PubMed1998

The use of heavy metal soil analysis for archaeological surveying.

An evaluation of the geochemical analysis of soils as an archaeological investigative technique is illustrated with reference to a site with a known history of human use and settlement. The results show certain elements, including the heavy metals Pb, Zn, Cd, Cu etc., to be associated with locations of past human activity, and support such analyses as significant additions to the means by which archaeologists might investigate the archaeological record.

Animals↗
PubMed1998

Relations of sit-up and sit-and-reach tests to low back pain in adults.

The sit-up and sit-and-reach tests are found on nearly all youth and adult fitness tests because of the perceived relation between performance on these tests and low back pain. However, this relationship has not been well validated. Therefore, the purpose of the study was to examine the relationship between performance on these two common field tests of muscular strength and flexibility (the sit-up and the sit-and-reach tests) and self-reported low back pain (LBP). The sample included 2,747 adults with a mean age of 44.6 +/- 9.8 years. The 1-minute sit-up (mean = 30.9 +/- 10.6) and sit-and-reach tests (mean = 39.88 +/- 10.49 cm) were administered to participants as part of a voluntary clinical health and fitness evaluation between 1980 and 1990. Participants completed a mail-back survey in 1990 on musculoskeletal health problems. Low back pain was quantified by developing on ordinal variable from questionnaire responses which represented a range of severity of LBP from none (0) to LBP which required medical care (3). With an average of 6.1 (+/- 2.0) years of follow-up, LBP was reported by 54% of the study participants (men = 45%, women = 54%). Pearson correlations between sit-up (r = .002; p = .94), sit-and-reach (r = -.043; p = .03), and LBP indicated poor LBP criterion-related validity from the sit-up and sit-and-reach tests. Partial correlations, where age, gender, percent of body fat, and time between testing and survey response were controlled, displayed no increase in the relationship. This study does not support the validity of sit-up and sit-and-reach test items for health-related fitness batteries because they were unrelated to LBP.

Adult↗
PubMed1995

A comparison of grip strength and selected psychomotor performance measures in healthy and frail elderly females.

Researchers have examined the relationships between strength and psychomotor skills among healthy male subjects far more thoroughly than among female subjects, especially elderly females. The purpose of the present investigation was to compare healthy and frail elderly females on grip strength and psychomotor performance measures. Nineteen healthy elderly females (M = 75.7 years of age) and 20 frail elderly females (M = 80.5 years of age) performed simple aiming movements in order for the investigators to obtain psychomotor measures (e.g., reaction time, movement time, kinematic movement characteristics). In addition, strength measures were obtained in the dominant and nondominant hands. Significant differences were found between elderly females on grip strength and psychomotor performance measures. In general, healthy subjects were stronger and exhibited superior control of movements (e.g., greater impulse, fewer movement adjustments).

Aged↗
PubMed1994

Pilot studies of 2 and 1 course carboplatin as adjuvant for stage I seminoma: should it be tested in a randomized trial against radiotherapy?

PURPOSE: Underpinned by increased confidence in cure of metastatic seminoma by chemotherapy during the past 12 years, three management strategies for Stage I seminoma have been evaluated by six collaborating centers within the Anglian Germ Cell Tumor Group. This paper evaluates the efficacy of surveillance, prophylactic radiotherapy and adjuvant chemotherapy, and discusses these differing management approaches. METHODS AND MATERIALS: Patients were recruited into the study between 1982 and 1992. There was no randomization between treatment groups. Seventy-nine patients received prophylactic radiotherapy (median follow-up = 51 months), 67 patients had surveillance alone (median follow-up = 61 months) and 78 patients were treated with adjuvant single agent platinum (median follow-up = 44 months). Fifty-three of these patients received two courses of platinum (median follow-up = 51 months) and 25 patients received one course (median follow-up = 29 months, range 22-72 months). RESULTS: There were 18 (27%) recurrences on surveillance, five (6%) after radiotherapy, one (1%) after two courses of adjuvant single agent platinum and none after one course of carboplatin. There was one death from testis cancer after radiotherapy and none after adjuvant chemotherapy treatments. Two patients died with drug resistant disease after relapse on surveillance. There was one death from a myocardial infarction after prophylactic radiotherapy and one death from suicide in the surveillance group. A retrospective quality of life questionnaire reviewing the incidence of early and late toxicity revealed no major differences though they suggest that those treated with one course adjuvant carboplatin had somewhat less sickness and an earlier return to work. CONCLUSION: Single agent carboplatin appears well tolerated and is an effective adjuvant treatment for Stage I seminoma. A multicenter randomized trial of the different treatment modalities is required to further evaluate its use.

Adult↗
PubMed1994

Interdevice reliability and validity assessment of the Nicholas Hand-Held Dynamometer.

The Nicholas Hand-Held Dynamometer (HHD) has been shown to have excellent interday and intraday reliability when using the same HHD. Since clinics may have more than one HHD with which to evaluate patients, it would be of value to know if two identical HHDs measure the same variable consistently. The purpose of this investigation was to assess interdevice reliability of the Nicholas HHD as well as to determine its validity. Thirty healthy female subjects between the ages of 20 and 56 years (mean age = 28.4) were tested for hamstring strength. Three measurements of maximum hamstring contractions were obtained using the first HHD (Device A). The average of these three measurements was compared with the average of three measurements obtained after a brief rest using a second HHD (Device B). Measurements from the two HHDs were also compared with measurements obtained from a Kin-Com isokinetic dynamometer. The Kin-Com measurements were used as criteria to determine validity of the HHD. An intraclass correlation coefficient (ICC) calculated to determine reliability between the two HHDs was low (ICC = .58). Pearson product-moment correlation coefficients were calculated between the Kin-Com and each of the two HHDs. These values were .85 and .83 for Device A and B, respectively. Analysis of variance showed no significant difference between the Kin-Com and Device A but a significant difference between the Kin-Com and Device B (p < .001). Measurements obtained from two identical HHDs may be significantly different and should not be compared.

Adult↗
PubMed1992

A comparison of results of a national cholesterol and blood pressure screening with the NHANES II Study: implications for further emphasis on reducing cardiovascular risk among Americans.

A comparison was made of serum total cholesterol and blood pressure levels taken from participants in a voluntary national health screening (N = 257,665) in 1988 with estimates for the general U.S. population from the NHANES II Study (1976-80). Although total serum cholesterol and blood pressure levels in the national health screening may be biased due to a higher proportion of females and whites, curvilinear age-related increases in mean total serum cholesterol (peak years 60-69) of approximately the same proportions among "desirable" to "high" classifications, and similar proportional increases in elevated blood pressure readings across age groups, were found in both the voluntary screening and NHANES II population estimates. Within and between gender-comparisons of total cholesterol and blood pressure measures showed greater risk among participants in the present study. The findings suggest that both blood cholesterol and blood pressure levels in the U.S. may not have decreased appreciably in the past decade, and that continued national, state and local public health efforts to modify behaviors related to hypercholesteremia and hypertension are warranted.

Adolescent↗
PubMed1992

Effects of exercise training on men seropositive for the human immunodeficiency virus-1.

We examined the effects of chronic exercise on fitness and immune status in Caucasian males (34.9 +/- 5.6 yr) diagnosed by Western blot as seropositive for the HIV-1 virus. The exercise regimen involved 12 wk of 1 h sessions 3 d.wk: 20 min of cycle exercise at 60-80% HRreserve was followed by 35 min of strength and flexibility training. After matching subjects on health status (modified Walter Reed criteria), subjects (N = 37) were randomly assigned to exercise or a counseling control condition. Changes in strength, responses to the YMCA cycle test, and serum lymphocytes were tested by MANOVA in a condition (exercise or counseling)-by-time (pretest, posttest) design with repeated measures on time. Results indicated significant (P less than 0.001) group-by-time interactions for strength (N.m) (chest press and leg extension) and for HR (beats.min-1) and total time (TT) on the cycle test at 150 W. Strength and TT increased and HR decreased in the exercise condition, while control subjects did not change. Total leukocyte, lymphocyte, CD4+, and CD8+ cell counts, and the CD4+/CD8+ ratio were statistically unchanged for each condition. We conclude that HIV-1+ men, including those symptomatic for AIDS-related complex, can experience significant increases in neuromuscular strength and cardiorespiratory fitness without changes in lymphocyte phenotypes or clinical diagnosis when the exercise regimen is prescribed and monitored in accordance with ACSM guidelines for healthy adults.

Adult↗